Where do oranges grow best?

Zone 8 Orange Trees – Tips On Growing Oranges In Zone 8

Growing oranges in zone 8 is possible if you are willing to take precautions. In general, oranges don’t do well in regions with cold winters, so you may have to take care in selecting a cultivar and a planting site. Read on for tips on growing oranges in zone 8 and hardy orange tree varieties.

Oranges for Zone 8

Both sweet oranges (Citrus sinensis) and sour oranges (Citrus aurantium) grow in U.S. Department of Agriculture plant hardiness zones 9 through 11. Although it is possible to start growing oranges in zone 8, you’ll have to take some precautions.

First, select cold hardy orange tree varieties. Try “Hamlin” if you are growing oranges for juice. It is fairly cold hardy but the fruit is damaged during hard freezes. “Ambersweet,” “Valencia” and “Blood Oranges” are other orange cultivars that might grow outdoors in zone 8.

Mandarin oranges are a good bet for zone 8. These are hardy trees, especially Satsuma mandarins. They survive in temperatures as low as 15 degrees F. (-9 C.).

Ask at your local garden store for hardy orange tree varieties that thrive in your location. Local gardeners can also provide invaluable tips.

Growing Oranges in Zone 8

When you start growing oranges in zone 8, you’ll want to select an outdoor planting site very carefully. Look for the most protected and warmest site on your property. Oranges for zone 8 should be planted in a full sun location on the south or southeast side of your home. This gives the orange trees maximum sun exposure and also protects the trees from cold northwestern winds.

Position the orange trees close to a wall. This could be your home or garage. These structures provide some warmth during dips in winter temperatures. Plant the trees in deep, fertile soil to protect and nurture the roots.

It is also possible to grow oranges in containers. This is a good idea if your area gets frost or freeze in the winter. Citrus trees grow well in containers and they can be moved into a protected area when winter cold arrives.

Select a container with adequate drainage. Although clay pots are attractive, they may be too heavy to move them easily. Start your young tree in a small container, then transplant it as it grows bigger.

Put a layer of grave in the bottom of the container, then add 2 parts potting soil to one part redwood or cedar shavings. Put the orange tree in the container when it is partially filled, then add soil until the plant is at the same depth as it was in the original container. Water well.

Look for a sunny spot to place the container during the summer months. Zone 8 orange trees need at least 8 hours per day of sun. Water as needed, when the soil surface is dry to the touch.

Citrus Fruit for Southern and Coastal Georgia

Arlie A. Powell, Former Extension Horticulturist

  • Historical Background of Citrus in the United States
  • Selecting Varieties
    • Sweet Types of Citrus
    • Acid Types of Citrus
  • Rootstock Selection
  • Pollination
  • Establishment and Care of Young Citrus
    • Tree Selection and Planting Procedures
    • Fertilization
    • Cold Protection
    • Cold Hardiness and Factors Affecting Freeze Damage
  • Care of the Bearing Tree
  • Other Cultural Problems
    • Fruit Shedding
    • Leaf Drop
    • Fruit Splitting
    • Insect and Disease Control

Citrus plants are very versatile around the home and may be used as individual specimens, hedges or container plants. Their natural beauty and ripe fruits make them attractive additions to the South Georgia home scene. Cold-hardy varieties that receive recommended care may grow successfully in the coastal and extreme southern areas of the state (and to a lesser degree in more northern locations). Areas where citrus are best adapted within the state are shown in Figure 1.

The most significant limiting factor to citrus culture in these areas is damage from severe winter temperature. The following brief history of citrus culture in the United States vividly illustrates the devastating effect of winter freezes.

Figure 1. Citrus is best adapted to Zone A. With adequate cold protection, cold hardy selections may be grown in Zone B with some success. Citrus can be grown in lower Zone C, but extensive cold protection measures will be needed in some years.

Historical Background of Citrus in the U.S.

Citrus was first introduced into the continental United States by early Spanish explorers at Saint Augustine, Florida, in 1565. Considerable time elapsed before citrus was introduced into Arizona (1707) and California (1769).

History indicates that citrus plants have been grown for many years in gardens near the Gulf of Mexico and even as far north as Charleston, South Carolina. Small satsuma plantings were developed in the Gulf states as early as the 1890s but were destroyed by the freezes of 1894-95 and 1899. Plantings resumed until the freeze of 1916-17 struck, killing thousands of acres. By the early 1940s the hardy satsuma had again made a comeback, with some 12,000 acres growing in the Gulf states of Louisiana, Alabama and northern Florida. But freezes in the two decades following World War II mostly eliminated these plantings. Currently the main commercial areas are on the Gulf Coast of Louisiana and Florida.

Selecting Varieties

Sweet Types of Citrus

The three general classes of citrus that produce sweet fruits are mandarins, sweet oranges and grapefruit. All of these citrus types develop into attractive, medium- to large-size trees. However, some are better adapted to South Georgia conditions than others.

Mandarins

This citrus class includes a large group of loose-skinned, deeply-colored, highly-flavored fruits. They are sometimes referred to as the kid-glove (easily peeled) fruits. Within this group are the mandarins, satsumas, tangerines and tangerine hybrids. The terms mandarin and tangerine are used interchangeably for a number of loose-skinned fruits, depending upon where they are grown. For example Dancy is called a tangerine in Florida and a mandarin in California. Unlike other types of citrus, crosspollination is required for optimum fruiting of a number of tangerine varieties and hybrids.

Satsuma

The highest degree of success and greatest satisfaction in growing citrus in Georgia will be realized with the satsuma. It will withstand colder temperatures, produce more consistent crops over a longer period of time and requires less cold protection than other types of sweet citrus.

The satsuma is distinctly different from the mandarin. It is self-fruitful, has excellent cold hardiness and ripens its fruit well ahead of any freeze problems (September to November). Owari is the most popular variety, and is generally available at retail outlets. Fruits retain their peak quality for about two weeks, after which they may become puffy, rough in appearance and lose flavor and juice content. Silverhill is another good variety. Changsha is seed-propagated. Some have good flavor, but most are very seedy.

An important fact to remember when growing satsumas is that fruits become fully ripened for eating while the peel color is still rather green. Certain fruits will ripen ahead of others, but by beginning to harvest when the first few fruits become ripe, at least one to two weeks may be added to the length of the harvesting period.

Tangerines (Mandarin)

The next best type of citrus to plant from the standpoint of cropping and cold hardiness is the tangerine. Satsumas and tangerines will escape damage from many freezes that will severely damage grapefruit and sweet oranges.

Dancy and Ponkan are exceptionally good tangerine varieties that produce quality fruits. However, their fruits may not develop good flavor before early- to mid-December, so they may be exposed to freezing temperatures before attaining optimum ripeness. The Ponkan reportedly is less cold-resistant than most mandarins. Its fruits lose quality and the rind puffs if it is not picked when ripe. Earlier-ripening selections such as the Clementine (Algerian) tangerine should be planted where possible. Dancy and Ponkan are self-fruitful, but Clementine requires cross-pollination from another tangerine or tangerine hybrid. The tangerine hybrids described below provide some exceptionally good early-maturing varieties that should be of interest to the homeowner.

Tangerine Hybrids

Tangelos are tangerine-grapefruit hybrids that produce loose-skinned, tangerine-like fruits. Orlando is an ideal selection for homeowner use. It is cold hardy and produces excellent quality fruits that ripen early (October to December). Dancy, Clementine or some other variety should be planted with Orlando for cross-pollination. Other early-season (October to November) tangerine hybrids that could be grown include Lee, Robinson, Osceola, Nova and Page. All of these hybrids require cross-pollination for best fruiting.

Sweet Oranges

Sweet oranges may be grown along the lower coastal area with a fair degree of success if adequate cold protection is provided each year. Hamlin is suggested if fruits are desired primarily for juice. Its cold-hardiness is equal or superior to other sweet orange varieties; however, hard freezes (20 degrees F and lower) will severely damage them. Fruits are commercially seedless (six seeds or fewer per fruit) and ripen early (October to November). Ambersweet is another sweet orange suggested for trial.

The naval orange is recommended for growing seedless fruit that will be eaten fresh. Navel oranges often produce light crops and aren’t usually as fruitful as sweet orange varieties (non-navel types) such as Hamlin. Suggested varieties include Washington, Dream and Summerfield. All ripen their fruits relatively early (October to December).

Grapefruit

Because of a lack of outstanding cold hardiness, grapefruit should be grown along the same lower coastal area as sweet oranges. Although numerous selections are available, the Marsh (white seedless) and Redblush or Ruby (red seedless) varieties are the most frequently planted. Both produce excellent quality fruit and have few to no seeds. (For those homeowners who prefer exceptionally high fruit quality, the white seedy varieties Royal and Triumph are suggested.) Marsh and Ruby fruits may be harvested as early as late September and October, but their quality significantly improves if they remain on trees until November and December. The Star Ruby, released by Texas A&M University, is an outstanding red, seedless grapefruit.

Acid Types of Citrus

There are a number of hardy acid-type fruits available for homeowner use. These plants make attractive ornamental specimens and provide delightful fruits. All are self-fruitful and do not require cross-pollination.

Kumquats

Kumquats are the most cold hardy of the commonly grown acid citrus fruits, tolerating temperatures as low as 15 to 17 degrees F. They possess a delayed resumation of growth in the spring, which helps avoid late freeze damage. The kumquat is one of the most widely used citrus plants around the home and develops into an attractive shrub-like tree that bears small orange-like fruit about one inch in diameter. Fruits may be eaten fresh, peel and all, or used in making jellies, marmalade and candies. Several varieties are available, but only three are commonly propagated: Nagami, Marumi and Meiwa. Nagami fruit are oblong to pear-shaped and have acid pulp; the others are sweeter and rounder. Meiwa, which produces nearly-round, sweet fruit, has become one of the most popular for home planting.

Calamondins

This small, round fruit looks somewhat like a tangerine and has very acid pulp. It is attractive as an indoor or container plant. Fruits are yellow to orange colored, and are readily used as a substitute for limes and lemons. Calamondins have good cold hardiness (low 20s).

Lemons

Meyer, one of the most cold-hardy lemon selections, is recommended for home planting because it produces good crops of large, practically seedless, juicy lemons. The fruit ripening period usually lasts for several months, beginning in late summer. Plants developed from cuttings are often used around the home. Inherent cold hardiness approximates that of the sweet orange (mid 20s).

Lime Hybrids

The Eustis limequat is a very cold-hardy lime-kumquat hybrid and makes a very attractive small plant. It is popular as a container plant. Limequats produce fruit resembling the lime in appearance and quality and may serve as an excellent lime substitute. Cold hardiness is about equivalent to the tangerine (low 20s). Lakeland and Tavares are two less-popular varieties occasionally found in retail outlets.

Rootstock Selection

Proper rootstock selection is crucial. Trifoliate orange (Poncirus trifoliata) is a superior rootstock for satsumas, oranges, kumquats and tangerines and is strongly recommended. It induces good cold hardiness in the scion variety and results in favorable yields and high fruit quality. About the only other rootstocks of value are sour orange, Cleopatra mandarin and certain citranges (a cross of sweet orange and trifoliate orange) such as Rusk and Carrizon. Cleopatra mandarin is an outstanding rootstock for mandarins-tangerines. Sour orange is incompatible as a rootstock for kumquats.

Pollination

With the exception of Clementine tangerine and certain tangerine hybrids such as Orlando tangelo, citrus trees are self-fruitful and do not require cross-pollination. Self-fruitful types of citrus may be grown as single trees.

Establishment and Care of Young Citrus

Site Selection and Spacing

Citrus trees produce fruit best when grown in full sun. Citrus trees planted under live oaks or pines produce only light fruit crops, but often survive freezes since warmer air may be trapped under the sheltering trees.

Avoid planting trees near septic tanks or drain fields. Tree roots may clog the drain, and soaps and cleaning supplies, used in the home may prove toxic to the trees.

Citrus trees do best on well-drained sandy loam soils, but will grow on many soil types if good water drainage is provided. If drainage is problem, plant on wide raised beds. Citrus plants that develop into trees, such as satsumas and tangerines, may be planted as close as 10 to 15, feet apart although a spacing of 15 to 20 feet is ideal. Small citrus plants such as kumquats may be spaced as close as six to 10 feet.

If possible, locate citrus plants in a protected area, such as near a home or some other structure, preferably on the south side. This type of location provides maximum protection from severe freezes. Usually the wind associated with South Georgia cold weather comes from the north to northwest.

Tree Selection and Planting Procedures

Most citrus trees for home plantings are purchased in containers, or balled and wrapped in burlap. Healthy one-year-old budded trees should be ½- to ¾-inch in caliper and two-year old trees usually measure ¾- to 1¼-inches in caliper (caliper is trunk diameter measured one inch above bud union). These trees are the ideal size for home planting. Acid-type fruit plants are usually purchased in smaller sizes. Planting can be done any time during the year, although late winter to early spring (after danger of freezing temperatures has passed) is ideal. A planting site four to five feet in diameter should be cleaned of all weeds and grasses and the soil thoroughly spaded.

Dig a hole large enough to accommodate the root ball. Remove the plant from the container and place it in the hole, keeping the top of the root ball level with the soil surface. If the tree is pot-bound, make vertical cuts at several locations around the ball to stimulate new root development. Fill the hole about one-half full with soil, add water and tramp firmly to settle soil and remove air pockets. Allow the water to settle, finish filling the hole with soil and apply water again. Pack the soil firmly around the trunk, adding additional soil if needed. Do not apply any fertilizer in the planting hole, as root damage may result. Around the tree, construct a water basin 30 to 36 inches in diameter and four inches high. Water twice weekly for the first two weeks unless rainfall is adequate. Gradually reduce the number of waterings to once weekly during periods of little or no rainfall.

The first growing season is critical in the life of a citrus plant. Water is essential. Keep an area at least four feet in diameter beneath the tree free of weeds and lawn grass to minimize competition for nutrients and water. If dense lawn grass is allowed to re-establish close to the tree trunk, the small tree will grow rather slowly because of intense competition.

At the time of planting, the branches should be cut back to six- to 12-inch stubs (this pruning is sometimes already completed when plants are purchased). This practice helps balance the top of the tree with the functional root system and stimulates vigorous regrowth. Very little pruning should be required during the first growing season except to remove sprouts that arise below the scaffold limbs (the primary structural branches originating from the tree trunk).

Ideally, scaffold branches should not be allowed to develop lower than 18 to 20 inches from the soil. The natural branching habit of citrus results in structurally sound trees; thus, the type of tree training normally practiced with peaches and apples is unnecessary.

Fertilization

Newly-planted trees should not be fertilized until growth begins in the spring. If possible, use a complete fertilizer such as an 8-8-8 or 10-10-10, which contains micronutrients. A suggested fertilizer schedule for the first three years is given in Table 1. Fertilizer applications should not be made between August 1 and February 15 during the first two years to avoid inducing untimely growth flushes during the winter.

During the first year, spread fertilizer in a 30-inch circle, and avoid placing any against the trunk. In subsequent years the fertilized area should be gradually increased. A good rule of thumb is to fertilize an area twice the diameter of the tree canopy.

Ordinary lawn and shrub fertilizer may be used for citrus trees; however, it fertilizer may only contain the primary plant food elements nitrogen, phosphorus and potassium. For the best performance, apply a fertilizer containing the secondary and micronutrients (magnesium, manganese and copper). The latter two elements, plus zinc and boron as needed, may also be supplied through nutritional sprays. Some garden centers and nurseries sell special citrus fertilizers that incorporate micronutrients.

Table 1. Suggested Fertilizer Schedule for Young Citrus Trees*
(Lbs. of 8-8-8 fertilizer per tree)
Growing Season March 1 April 15-30 June 1-15 July 15-30
First 1/3** 1/2 2/3 1
Second 1 1 1/4 1 1/2 1 3/4
Third 1 3/4 2 2 1/2 3
*This schedule is designed for citrus plants that develop into medium to large trees. Only half these amounts, or less, will be needed for small, shrubby citrus plants such as kumquats, limequats, calamondins, etc.
**Make this application after growth begins in the spring, usually four to six weeks after planting.

Cold Protection

Even the most cold-hardy young citrus trees cannot withstand freezing temperatures as well as more mature, bearing trees. Before the first freeze, trees up to four years of age should be banked with clean soil to a height of about 15 inches. Soil banks should be removed after the last chance of freeze in the early spring. Wrapping material with good insulating properties such as fiberglass or foam rubber also make effective protectors and may be used in lieu of soil banks. These materials should be a minimum of six inches thick and must make good contact with the soil. Special microsprinklers can also be used to protect the trunks during freezes. When the trees grow larger, the microsprinkler is placed in the lower part of the in the tree to protect the trunk and lower scaffold limbs.

When only a few plants are involved, protective covers may be used when severe freezes occur. On extremely cold nights, placing one or two electric light bulbs beneath the cover provides good protection.

Sprinkler irrigation can also be used to protect citrus during somefreezes. Start applying ¼-inch of water per hour when temperatures drop below freezing and continue until temperatures rise above 32 degrees F. If possible, support weak limbs to prevent breakage from ice. The ice should be clear and icicles should be present. If the ice is milky white, increase the volume of water being applied. See www.smallfruits.org for a chart to determine if overhead irrigation can be used for freeze protection.

Cold Hardiness and Factors Affecting Freeze Damage

Citrons, lemons and limes are most easily killed by freezing temperatures. Temperatures from the mid- to high-20s will readily kill or severely damage these plants. Sweet oranges and grapefruit are somewhat more cold hardy and usually require temperatures in the low- to mid-20s before incurring major damage to large branches. Tangerines and mandarins are quite cold hardy, usually withstanding temperatures in the low 20s before significant wood damage occurs. Among the edible types of sweet citrus, the satsuma has the greatest degree of cold hardiness. Properly hardened bearing trees will withstand temperatures as low as 19 to 20 degrees F without appreciable wood damage.

Citrus fruits, on the other hand, easily freeze at 26 to 28 degrees F, especially when these temperatures last for several hours. A longer duration of freezing temperatures is required to freeze grapefruit than sweet oranges, and tangerines and satsuma fruits are more easily frozen than either of the former.

The particular temperature at which tissue of a given plant will freeze and the degree of the damage sustained are functions of a number of factors in addition to the species and variety involved:

  • the freezing temperature reached;
  • the duration of the minimal temperature;
  • how well the plant became hardened or conditioned before freezing temperatures occurred (the tissue freezing point of a hardened citrus plant may be five to six degrees lower than an unhardened plant);
  • whether the plant is wet or dry (the killing temperature is two to four degrees lower for a dry citrus plant); and
  • the age of the plant (a young plant cannot withstand as much cold as a more mature tree).

Some years, citrus plants seem to freeze at higher temperatures. The contributing factor seems to be the difference between air (ambient) temperature and leaf (tissue) temperature. On a windy night with clear or cloudy skies, leaf temperature will be approximately the same as air temperature. On a cold, clear night with little or no wind movement, leaf temperature may easily drop 3 to 4 degrees F below air temperature because of radiation heat loss. Thus, under the latter circumstances, while the minimum air temperature on a given night may have only been 25 degrees F, actual leaf temperature may have reached 21 to 22 degrees F. The critical temperature is that of the leaf or fruit, not the air.

Care of the Bearing Tree

The first three years should be devoted to developing a vigorous tree with strong scaffolds. Some fruit may be borne the second and third growing seasons, although the quality may not be too good. Trees should begin fruiting significant crops in the fourth growing season.

Continue using the same 8-8-8 fertilizer (or equivalent) for bearing trees. Three applications per year, in February, May or June and August or September, are suggested. Apply fertilizer from near the trunk to well beyond the leaf drip of the tree (on large trees this usually involves fertilizing about four to six feet beyond the leaf drip). A reasonable rate of application to maintain healthy foliage and good fruiting is about a half of a pound of the 8-8-8 fertilizer per year of tree age (rates are for sandy soils; clay and other soils with greater inherent fertility require less fertilizer). After a number of years, a fertilizer containing nitrogen and potassium or just nitrogen alone may prove adequate. A maximum of 1½ to 3 pounds actual nitrogen per tree per year should be adequate.

As trees age, problems may be encountered with micronutrient deficiencies. An annual nutritional spray applied in the spring usually corrects the deficiencies. Pre-packaged nutritional spray mixes may be purchased from garden supply dealers. These mixes should contain manganese, zinc and copper. Boron deficiencies may be corrected with foliar sprays or soil applications. When iron deficiency symptoms develop, chelated forms should be applied to the soil.

The pH (acidity or alkalinity) of the soil in which trees are growing should be maintained between 6.0 and 7.0. Apply dolomite, agricultural limestone or basic stag as needed to prevent the pH from dropping below 6.0. Your local county Extension agent or garden supply dealer can assist in determining if a pH adjustment is needed.

Weed control around large bearing trees becomes somewhat less essential. However, it is generally beneficial to remove all weeds and lawn grass from beneath the canopy of the tree. This approach also provides a more attractive landscape design. Do remove weeds and grass from the area immediately around the tree trunk as this growth tends to create ideal conditions for fungal organisms such as those causing foot rot at the base of the tree. Mulches are not necessary for best tree performance, but may be used on well drained sites. Mulching material should not be placed within 12 inches of the trunk.

Watering bearing citrus plants will not be necessary in some years. However, adequate water should be provided as needed, particularly during flowering and fruit setting in early spring and the dry periods of mid- to late summer. A slow application of water over a several-hour period is preferable to a rapid “lawn-type irrigation.”

Pruning citrus trees on an annual basis is unnecessary. Only remove water sprouts (suckers) and dead, damaged or diseased limbs. Make all cuts flush with the trunk or the next-largest branch (don’t leave stubs). Seal all cuts in excess of ½-inch in diameter with a safe pruning paint—those with an asphalt base are recommended. The summer is usually an ideal time for pruning.

Citrus plants in Georgia are always subject to injury from cold weather. If trees are only slightly damaged, pruning may be done as soon as new growth indicates the extent of injury. However, regardless of the amount of injury sustained, no pruning should be done until after danger of further freezes has passed. If trees incur major freeze damage, allow the first flush of growth to mature before pruning.

Other Cultural Problems

Fruit Shedding

Homeowners frequently become concerned about the excessive shed of young blossoms and fruits in early spring. This is a natural shedding of blossoms and fruits that is characteristic of all citrus. Another natural fruit shedding occurs in May and June when fruits are marble-size. Keep in mind that only one or two percent (sometimes less than one percent) of the blossoms are needed for good crops. Natural shedding of flowers and fruits prevents citrus from overproducing.

Leaf Drop

Occasionally homeowners become alarmed when healthy trees lose large numbers of their leaves. In many cases this is a natural drop; and may be most noticeable in early spring. Citrus leaves live for 18 to 24 months and then begin shedding, with some leaf dropping occurring throughout the year. Always be alert to other possible causes of leaf shedding, including mite damage, excessive or insufficient soil moisture, cold damage or root diseases.

Fruit Splitting

In late summer (August to September), fruit splitting may be a problem with certain oranges and tangerines. This is a physiological problem that usually occurs when a period of fruit growth cessation (associated with moisture stress) is followed by a rapid increase in size as the result of a heavy rain. Other than alleviating moisture stress, little can be done about this problem.

Insect and Disease Control

Citrus fruits may be grown successfully in the home or backyard orchards with limited control of insects and diseases. Fruits produced without pesticide sprays may have very poor external quality as a result of mite, insect and fungus disease damage. The tree appearance may suffer, but they are seldom critically damaged by most citrus pests. Natural biological control will assist in maintaining pests at low population levels.

For those who prefer to spray, three cover sprays during each season are helpful. A post-bloom spray for scales, mites and fungal diseases, a summer oil for scales and mites, and a fall mite spray are usually satisfactory.

Formulating a spray program can be somewhat difficult because of the many factors involved, including constantly changing government regulations regarding the use of agricultural chemicals. Consult your local county Extension agent for information on developing a spray program for home citrus trees.

Cover photo from Photobucket.com

Status and Revision History
Published on Jan 08, 2009
Published with Full Review on Feb 14, 2012
Published with Full Review on Feb 22, 2015

Citrus Tree Care

Growing citrus trees is fun and rewarding, although there are a few things you must remember to ensure that the dwarf citrus tree for sale you bought will grow healthy and become fruit bearing.

Climate

The Valencia orange tree is a subtropical tree that thrives under the sun and best planted in USDA hardiness growing zones 9 thru 11. It needs 6-8 hours of sunlight every day & temperatures ranging from 55 to 100 degrees Fahrenheit to grow and ripen their citrus tree fruit. The color of the rind becomes more intense in dry climates, while humid climates cause the fruit to become sour and less juicy. Furthermore, although Valencia orange trees can withstand drought, the fruit production declines and the oranges become smaller if exposed to dry climates.

Soil

Like all citrus trees, Valencia orange trees like light, well-drained acidic soil that is rich in nitrogen. If the leaves turn yellow, you need to make the soil more acidic by applying magnesium sulfate solution to the soil.

Water

A deep watering method is applied when growing citrus trees. Newly planted trees should be watered once to twice a week for the first few weeks to keep the soil moist. Once established, water the orange trees once every 2 weeks, depending on the weather in your area or the type of soil. Cut back to watering once every three weeks during autumn and winter. Remember, the key is to keep the soil moist but not wet since standing water or wet soil can kill your dwarf citrus tree. To easily determine the moisture level of the soil, purchase a water meter. When the meter reads under 50 per cent moisture, it is time to water the tree.

Cold Protection

Valencia orange trees can tolerate cold weather but needs to be protected when the temperature reaches 28 degrees F or below. You can either plant the tree on the south side of your house or cover your tree with a blanket with a plugged light bulb to keep the frost out and keep the warmth in.

Citrus Tree Fertilizer

Be it orange tree for sale or home grown from seed, a growing dwarf Valencia orange tree needs citrus fertilizer. One of the main causes of yellowing leaves and low fruit yield is nitrogen deficiency. Fruit trees consume the nitrogen in the soil and turn it into fruit. Nitrogen deficiency can be addressed by using 2/1/1 fertilizer for citrus trees, with nitrogen being the first number and is double the amount of the other two. You can fertilize in February, May and the start of October. If you are in the south, avoid fertilizing in October as it may encourage growth during winter when there is a danger of frost or sustained freezing weather.

Dwarf Valencia Orange Tree in Pots

Dwarf Valencia orange trees have a shallow, extensive root system and should be planted in a pot that is wide in diameter rather than a deep container.

Hamlin sweet orange

Citrus sinensis L. Osbeck

CRC 3862

PI 539626

Photos by Toni Siebert and David Karp, CVC. Photo rights.

Source: Received as a seedling from USDCS, Indio, Ca, 1961.

Parentage/origins: Parents unknown.

Rootstocks of accession: Carrizo citrange, C-35 citrange

Season of ripeness at Riverside: Unknown at this time.

Notes and observations:

Six seedling budlines fruited at Lindcove; all appeared identical. Seed had come from tree of Hamlin at USDCS.

2/8/1988, EMN: Average good size, few seeds, flesh appears somewhat coarse in cross section, good flavor (early).

Description from The Citrus Industry, Volume 1:

” Fruit medium-small, globose to slightly oblate; sometimes with low radially furrowed collar and faint areolar ring; seeds very few or none. Well-colored at maturity (one of the best in Florida). Rind thin, with smooth, finely pitted surface. Flesh well-colored; tender, juicy, lacking in acid; flavor sweet. One of the earliest to mature.
Tree moderately vigorous, medium-large, productive, and more cold-tolerant than most.
The Hamlin variety originated as a chance seedling in an orchard near Glenwood, Florida, which was planted in 1879, and was named for the owner, A. G. Hamlin, at the time its value was recognized some years later. It came into prominence following the great Florida freeze of 1894-95 as a rival of Parson, the only other variety of similar early maturity, and has gradually replaced it. Currently, it is a major variety in Florida, of considerable importance as an export variety in Brazil, of limited importance in South Africa and elsewhere, and possibly the world’s principal variety of very early maturing common sweet orange.
In semitropical climates characterized by high heat and humidity, this variety produces fruit of satisfactory size for marketing fresh, although the eating quality is generally somewhat disappointing. In arid, subtropical climates, fruit size is commonly smaller than desirable though the quality may be satisfactory. ”

Availability: Not commercially available in California.

USDA Germplasm Resources Information Network page for Hamlin sweet orange

How to Grow Hamlin Orange Trees in Pots

small orange tree image by Ergün Özsoy from Fotolia.com

Any citrus tree can be grown in a pot. The Hamlin orange is a favorite because of its early ripening season. The tree produces small oranges that are very sweet and juicy. While trees in pots will not produce as much fruit as trees planted in the ground, growing citrus trees in pots is a great way for those who do not live in warm areas to still experience the taste of homegrown tropical and subtropical fruit.

Choose a large planting container that has drainage holes. The pot should be as large as possible, yet it shouldn’t be so large that you are unable to move it with a dolly.

Line the bottom of the pot with wire mesh. This will keep the soil from running out the holes when the tree is being watered.

Fill the pot halfway full of potting soil.

Remove the tree from its container and place it in the pot. Add more potting soil, if needed, to elevate the original soil and tree up to within 1 to 3 inches of the pot’s rim. Continue filling the pot with soil.

Water the tree thoroughly. After the water has drained add more soil, if needed, to bring the soil line within 1 to 3 inches of the pot’s rim.

Place the pot in full sunlight. Avoid placing your tree in shady areas as this will cause weak growth.

Water the tree whenever the top 2 inches of the soil dries out.

Fertilize the tree monthly with a balanced tree fertilizer when new growth develops. Follow the dosage recommendations on the manufacturer’s label. Discontinue fertilization when the tree goes dormant. Start monthly fertilizer applications again the following spring.

Prune any damaged, dead or unhealthy branches as soon as they are identified. If the tree consistently drops leaves or it produces leggy growth, cut and remove one third of the branches. This will encourage bushier growth. This type of heavy pruning is best done in late winter or very early spring.

Move trees into a winter-safe place indoors as soon as frost is expected in your growing region.

Growing Seasons Chart

We grow many varieties of citrus & have made this chart to help you understand their seasons. Mother Nature can cause seasonal variations from year to year.

* indicates seedless fruit
Y indicates a great juicer!
z indicates an excellent peel flavor, choice for zest

Ojai Sweet Oranges

* z Navel Oranges: ripe in winter months December-April

Varieties we grow include Washington, Cara Cara, and Late Navel.

Considered the “eating orange”, these oranges are seedless and easy to peel and are a favorite snack in the winter! They have a thicker peel and lower juice content than Valencias making them superb for eating and using in salads. The Cara Cara variety has a red hue.

Y z Valencia Oranges: ripe in the early spring to early winter (April-December)

Considered the “juice orange”, these oranges are packed with juice, making peeling them messy; best to cut up for eating. Valencias can regreen during the hot weather of summer, so don’t be fooled by bad looks. Late-summer Valencias are the best oranges we grow! Midknight Valencias are a seedless variety.

Y z Blood Oranges: ripe in winter (mid-January-April)

Varieties we grow include Moro, Tarocco and Sanguinelli.

All varieties have a red pigmented flesh due to more natural pigments with antioxidant qualities. They have a strong aroma and a spicy taste, fresh and pleasing in the winter months.
Of the varieties Friend’s grows the Moros have the reddest flesh and Taroccos the best flavor. Blood oranges make excellent and attractive juice especially when mixed with other citrus.

Ojai Tangerines/Mandarins

* Satsuma Mandarins: ripe in winter, usually starting around Thanksgiving

The first mandarins in season after summer, just in time for the winter holidays! These juicy treats are packed with their own distinctive almost-tropical flavor. They have a zipper
skin and are seedless, making them a perfect natural snack. Friend’s picks and sells them with a few leaves attached making a very attractive display for your fruit bowl or holiday table
arrangement.

Y Dancy Tangerines: ripe January through March

Dancys are one of the traditional favorites among tangerine lovers. Their amazing flavor has made them one of the most widely grown tangerines in the world. They are easy to peel. Don’t let their seeds deter you from snacking on these tasty treats! Also great for juicing! Friend’s picks and sells them with a few leaves attached making a very attractive display
for your winter fruit bowl or lunchroom.

Clementine Mandarins: ripe in December and January

Clementines were originally called Algerians. Folks from Europe and the east coast know Clementines well as they are grown throughout the Mediterranean and exported to the eastern US and throughout Europe. They are only seedless if grown in isolation from other citrus (if they cross pollinate with other citrus they will by seedy). Medium-sized fruit, easy
to peel with a smooth and glossy look. Fruit has a distinctive flavor with a slight essence of apricot. There are many varieties of clementines, our favorite is the Fina Sodea, a very flavorful and juicy variety.

Y z Lee Tangerines: ripe December through January

One of the best-flavored tangerines we grow! The season for Lees always comes and goes too quickly and one never seems to get their fill of this astounding fruit. Lees are quite
difficult to peel and do have seeds, but their flavor surpasses most other citrus. If you can’t get the knack of peeling them, try slicing them, or squeezing them for juice. Everyone loves
the flavor of a Lee Tangerine!

Y z Page Mandarins: ripe mid-January through March

Like Clementines, Pages will only be seedless if grown in isolation from other citrus varieties. The Page variety is a cross between a Clementine and Minneola. They have a very
attractive reddish peel, which is quite easy to remove, revealing a scrumptious fruit packed with juice. Friend’s only has a few trees of Pages, so they come and go quickly. They make
an excellent juice with a yummy sweetness!

Y z W.Murcott mandarins: ripe mid-February through April

W. Murcotts are a beautiful shiny, reddish mandarin with a distinct flavor. They are not truly seedless, and will only be absent of seeds if grown in isolation from other citrus.
Their easy peelabilty, beautiful color and juicy inside has made them into one of the most planted mandarins in California. (Much of the California W. Murcott crop is marketed under
the trade name Delite®).

* Y Tahoe Gold Tangerines: ripe in March and April

* Shasta Gold Tangerines: ripe mid-March thru May

* Y Yosemite Gold Tangerines: ripe in mid-March thru May

The Shasta, Tahoe and Yosemite Gold mandarins are excellent new varieties, all derived from crossing Tangors, Dancy and Encore mandarin varieties; hence they were initially called
TDE’s. All three are beautiful, large, seedless and very juicy. They are generally easy to peel, although can be messy if full of juice and have a fruity, Minneola-like flavor. All
3 have distinctive qualities, the Yosemites tend to be very large, the Tahoes are juiciest, Shastas are rounder and easiest to peel. Try all 3 and see which you like best!

* z Gold Nuggets: ripe in March and April

Gold Nuggets were originally called “Pixie-Likes” due to their similarities with the Pixie. Gold Nuggets are truly seedless, easy to peel, juicy and very sweet. An excellent
piece of fruit! A real hit with children, great for lunchboxes.

* z Ojai Pixies: ripe mid-March until we sell them all, which is usually mid-June

Our favorite and the first choice of our customers at farmers’ markets! Seedless, easy to peel, and very sweet. These little lumpy-bumpy wonders are the perfect snack for any age. They
have a low acid content and 1-year olds and elderly are able to eat them up without a worry. Fruit size and appearance varies, they can be pale colored or lumpy-bumpy, but they
are all great on the inside! Try a few and you will be hooked! We like them so much that we helped make a bumpersticker about them….see www.ojaipixies.com

Y Minneola Tangelos: ripe April through June

The Minneola is a cross between a tangerine and a grapefruit, making a very juicy flavorful piece of fruit with a slight tang to it. This fruit has deep-orange flesh with few seeds
and minimal pith. Try making Minneola juice, it is excellent on its own, mixed with other fruit juices, or used in your favorite cocktail!

Other Ojai Citrus

Y z Eureka Lemons: ripe year-round

The traditional sour lemon. We pick ours when they are just turning yellow, which is when they have the highest vitamin content and best flavor. These lemons are great for cooking
with as their flavor is not lost with the heat of cooking.

Y z Meyer Lemons: ripe in the winter (December through February)

A sweet lemon! The Meyer lemon is the result of the hybridization of a lemon and tangerine. These lemons have a very distinct flavor and aroma, making an excellent juice or garnish for just about any dish. Their flavor is lost somewhat with cooking, so try and use Meyer lemons fresh. Try quartering these lemons in a pitcher of water to make a refreshing drink!

Y Grapefruit: ripe in the summer months (May through September)

Friend’s grows both white and pink varieties. White grapefruit tend to be more acidic, but with a more intense flavor. Our pink grapefruit tend to not color-up and sweeten until we’ve
had a few weeks of hot summer days. Both make excellent juice and are an excellent refreshing summer snack!

Ojai Avocados

A note: Avocados bruise easily even when hard (unripe)! Treat them gently whether they are ripe or not and you will have a much better piece of fruit. Many avocados in grocery
stores have been mishandled, resulting in those nasty brown spots and off-flavored fruit when they get ripe.

Bacon Avocados: ripe in the winter (December through March)

As the first variety to mature in the fall, many are picked and sold too early. A green skinned avocado, which does not turn color when ripe. Ready to eat when very soft to the touch
at both ends. Bacons have a thin skin and bruise easily. A very creamy, sweet avocado. Excellent for salads as they fall apart and make their own dressing. They can also be blended
fresh with oil and vinegar for a dressing. Also good for guacamole and sandwiches!

Fuerte Avocados: ripe in February and March

Fuertes were once the #1 avocado grown in California due to their excellent flavor and ability to withstand cooler temperatures. A green skinned avocado, which does not turn color when ripe. Fuertes are ready when soft to the touch at both ends. Fuertes are our favorite avocado for flavor with a subtle smoky flavor and balanced texture. Try them side-by-side with other varieties and see which you like!

Pinkerton Avocados: ripe in March and April

The Pinkerton variety originated from a seed of a Hass avocado that had been pollinated by another variety. Pinkertons are green skinned and do not turn color when ripe. They are ready when soft to the touch at both ends. Pinkertons are similar to Hass with a thicker skin, an excellent flavor and nice texture, but with a little less oil than a Hass.

Hass Avocados: ripe in the late spring (March through June)

The most widely grown avocado worldwide. The Hass is green skinned when immature and the skin blackens as it ripens. Ripe Hass will be evenly black and soft to the touch. Hass
have excellent flavor, nice texture and are easy to separate from the skin and pit.

A food production wiki for public health professionals

Key Facts

  • Likely native to Southeast Asia, sweet oranges are now commercially grown for fresh and processed (i.e., juice from-concentrate or not-from-concentrate) consumption.
  • Throughout the global tropical and subtropical growing regions (top producers are Brazil and United States) worldwide production slightly down, but still topped 11.2 million tons in the United States during the 2012-2013 growing season.
  • Orange juice has been implicated in 10 reported outbreaks, during which 810 persons became ill, in the United States from 1998 through 2012.
  • Confirmed pathogenic agents reported to the United States National Outbreak Reporting System in orange juice associated outbreaks are limited to Salmonella (S. saintpaul, S. typhimurium, S. muenchen, S. anatum, and S. enteritidis) and Norwalk-like virus; however, suspected chemical or toxin contaminates have been reported.

    Introduction

    The sweet orange (Citrus sinensis) is part of the genus Citrus that contains all citrus trees (e.g., oranges, grapefruits, lemons, limes, hybrids), which are interfertile. There are four distinct groups of sweet oranges including round oranges (most economically important), navel oranges, blood oranges, and acid-less oranges. While there is no universal agreement that the sour or bitter orange (Citrus aurantium) is a different species from C. sinensis, typically they are treated as separate species. While C. aurantium is produced and harvested in a similar manner as the sweet orange, uses differ. This article will focus on understanding the production process and health implications surrounding C. sinensis.

    Orange tree flowers.

    The C. sinensis tree, which is typically 22 to 30 feet (7 to 10 meters) in a pruned commercial grove, have 3 to 5 inch (8 to 13cm) long dark green evergreen leaves that last two to three years. The blade of the sweet orange leaf has a round base with pointed apex and typically has a small spine at the axil.

    The flower of the sweet orange is white and self-pollinating; although, bees do assist in pollination. Seedless fruit cultivars are produced by flowers with little to no pollen or fertile ovules.

    The sweet orange fruit is a spherical or oblong hesperidium that ranges in size from 2-1/2 to 4 inches (6 to 10cm) in diameter. The surface of the peel can be smooth to rough with pockmarks. The peel thickness ranges between a tangerine and grapefruit, and adheres tightly to the flesh of the fruit, except in navel cultivars.

    Sweet oranges were established in Florida between 1513 and 1565 near St. Augustine, with seeds having been imported from Europe. Commercial orange groves in Florida have continually been pushed further south to avoid fruit killing and impact freezes (kills juvenile and mature trees), most recently during December 1989. In the United States, Florida was the top producer of oranges for juicing, producing 6.3 million tons of oranges (88.9%). The next top producers in this category were California (8.7%), Texas (1.9%), and Arizona (0.4%) during the 2012-2013 growing season. In the same growing season, California was the top producer of oranges for fresh consumption, producing 3.2 million tons (76.6%), followed by Florida (17.6%), Texas (4.5%), and Arizona (1.3%).

    Common Sweet Orange Varieties

    A quick identification guide to the most common commercially grown orange varieties is presented below.,

    Round Oranges

    Sweet oranges on tree. Photograph by: Benjamin Klekamp

    Round Oranges are able to be harvested throughout the potential 10 month Florida orange harvest season by growing ‘early’, ‘mid-season’, and ‘late’ varietals. Hamlin, Pineapple, and Valencia are the principal varietals grown in their respective season in Florida. Round oranges are primarily processed (i.e., juice from-concentrate or not-from-concentrate).

    Hamlin

    The Hamlin orange is a varietal with ancestral roots linked to a fortuitous seed planting in the grove of namesake A.C. Hamlin near DeLand, Florida in 1879. Freezes during the 1980s allowed the Hamlin to replace the Parson-Brown as the dominant early-season orange varietal in Florida.

    With the harvest season beginning in October before the chance of a freeze of a commercially seedless fruit (0 to 6 seeds per fruit) and cold-tolerance of the tree combines to make the Hamlin very popular in Florida. The Hamlin fruit is 2-3/4 to 3 inches in diameter with a smooth, thin, and poorly colored peel. While the Hamlin is a heavy producer, consumers find the juice color to be poor. Therefore, typical commercial practice is to blend the juice with other varietals during production.

    Pineapple

    The Pineapple orange, named for the aromatic fragrance of the fruit, traces it’s roots back to a grove in Citra, Florida planted from seed in 1860. Known for it’s excellent juice color and quality, the Pineapple has a harvest season from December until February and is the dominant mid-season Florida varietal. The fruit is 2-3/4 to 3 inches in diameter and slightly flattened on each end. The peel, typically orange but can develop an appealing red-orange color if nights drop below 55 degree Fahrenheit, is smooth and thicker than a Hamlin. With counts ranging from 15 to 25 per fruit, the Pineapple is a seedy varietal and as a result is used almost exclusively in the processed market.

    Valencia

    Used in both the processed and fresh markets, the Valencia orange is the most widely grown sweet orange varietal in the United States and the world. While the economically important varietal has a disputed past, first accounts of importation to Florida occurred in 1877.

    The Valencia is Florida’s leading late-season varietal with the harvest season beginning in March and extending into June. Farmers have two unique challenges when growing Valencia oranges including fruits developing on the trees during the winter months (potential freeze damage) and the tree typically produces two crops past flower bloom. The fruit is 2-3/4 to 3 inches in diameter, commercially seedless (0 to 6 seeds per fruit), and notoriously juicy. The peel is thin and will remain green without cool nights even when the fruit is ripe. As a result, fruit bound for the fresh market may be treated with ethylene gas to turn the peel an attractive orange color consumers expect.

    Navel Oranges

    Navel oranges.

    A naturally occurring mutation is likely to have occurred in Brazil prior to the introduction of the Navel orange to the United States in 1870. This mutation provides the varietal namesake due to a unique second and sometimes tertiary embryo growth at the fruit apex, which is similar in appearance to the human navel. However, the mutation is unstable making selection of trees from a nursery of particular importance for growers.

    The Navel tree produces no pollen resulting in a commercially seedless (0 to 6 seeds) fruit. Species propagation is exclusively through budding and cloning. One of the original two parent Navel trees that all Washington Navels are descendants from was imported to Riverside, California in 1873 and is still producing fruit today. The Washington is second only to the Valencia among Sweet Orange varietal production both in the United States and worldwide. Unlike the Valencia, Navel oranges do not grow well in tropical climates; however, the sub-tropical climates of both Florida and Brazil produce quality fruit.

    The size among the over 50 Navel orange varieties can vary, but typically are on the larger side (3 to 3-1/2 inches in diameter) of the spectrum between tangerines and grapefruit. With a yellow to orange colored pebbled peel that is easy to peel and fruit with low acid concentration that is easily sectioned, the Navel is excellent for eating fresh. The juice is slightly bitter making the fruit less suitable for juicing. The Navel is harvested in Florida from October to January; fruit at the end of the season can taste and appear dried out.

    Cara Cara, or Red Navel, was discovered in Venezuela in 1976 with production today based in California, Venezuela, and South Africa. Harvest seasons of the Cara Cara typically lead to arrival from South Africa in August, Venezuela in October, and California in November.

    Blood Oranges

    Blood orange.

    The Blood orange is the product of a natural mutation in the sweet orange and is from the Mediterranean basin where it has been cultivated since the 15th century, especially in Spain and Italy.

    Smaller in size, the Blood orange (e.g., Moro, Ruby, Tarocco) has a diameter of 2-1/2 to 2-3/4 inches and is a pink blush fruit that can be oval, round, or oblate in shape. The varietal is known for its unique sweet flavor that is similar in taste and appearance to a Valencia, but with a deep red streaky pigment in the flesh. The deep red color is from increased concentrations of the pigment anthocyanin, which increases when growing conditions are cooler. As a result, Blood oranges grown in Florida typically do not have a deep red color due to the warm, humid climate. The fruit contains few seeds, ranging from four to ten.

    Acid-less Oranges

    Acid-less oranges (e.g., Lima) tend to be early-season varietals with remarkably little flavor. While grown for local consumption in the Mediterranean basin, Brazil, Egypt, Mexico, and Spain, due to the very low acid concentration these varietals are unable to be transported widely as they readily spoil.

      Foodborne Outbreaks

      From 1998 to 2014, there have been 11 outbreaks and 838 illnesses associated with oranges in the United States, with five outbreaks occurring in Florida. Of these outbreaks, four were caused by Salmonella, two were caused by norovirus, two were caused by a chemical/toxin, and three were of unknown etiology. Outbreaks associated with oranges and orange juice have led to various policy changes and recalls.

      Three outbreaks have been associated with orange juice served at hotel breakfasts. In 1944, an outbreak of Salmonella Typhi in Ohio caused illness in 18 individuals. In 1989, an outbreak of Salmonella Typhi in a New York hotel caused illness in 70 individuals. Salmonella Typhi is the pathogen that causes typhoid fever; both outbreaks were attributed to an asymptomatic food handler preparing breakfast for hotel guests. In 2004, an outbreak associated with the consumption of unpasteurized orange juice served at a hotel in Egypt was the source of a Hepatitis A outbreak, causing 351 individuals to fall ill across nine countries. An investigation of the orange juice processing facility indicated that working conditions were unsanitary and the orange juice was not properly heat treated. Results concluded the presence of a dose-response relationship; the number of days of orange juice consumption was directly proportional to infection.

      Multiple outbreaks associated with unpasteurized orange juice have been linked to Salmonella. In 1995, unpasteurized orange juice served in a large Florida theme park caused 72 illnesses across 21 states. This multi-state outbreak of Salmonella Gaminara was linked to contamination during processing. In response to this event, the theme park decided it would only sell pasteurized orange juice and the Florida Department of Citrus issued new regulations for the production of unpasteurized fresh squeezed orange juice. In 1999, separate clusters of Salmonella Muenchen were identified by the Washington state health department and the Oregon Health Division., Further investigation revealed a multi-state outbreak of 207 confirmed cases across a total of 15 states and two Canadian provinces., The source was determined as unpasteurized orange juice from Sun Orchard that was distributed under multiple brand names., Sun Orchard voluntarily issued a recall in response to the outbreak., In 2005, a multi-state outbreak of 152 cases across 23 states was caused by Salmonella Saintpaul and Typhimurium. Both pathogens were found in unpasteurized orange juice from the same company. Although the source of contamination was not identified, noncompliance with the juice Hazard Analysis and Critical Control Point (HACCP) regulation likely contributed to this outbreak.

        Production

        Planting

        “Distribution of commercial sweet orange production in Florida. With very few exceptions, production is limited north of the line shown on this map.”

        The juvenile period, where there is no fruit production, of a sweet orange tree grown from seed is approximately 8 to 12 years. Cultivars have reduced this time period to approximately 3 years by grafting a bud from the desired fruit tree (scion) onto a stem of a young seedling (rootstock) grown in a nursery. Rootstock is selected based on cold tolerance, pest resistance, and influence on the productivity, quality, and vigor of the type of scion attached.

        Orange groves are laid out in rows to maximize space, sun penetration, and harvest efficiency. As land and water have become more scarce in Florida, the within-row spacing of orange grove trees has decreased from 25 feet to 15 feet. The between-row spacing has remained constant overtime at 25 feet. Herbicide is applied under the planted tree to reduce competition for nutrients, reduce pest habitat, and allow free percolation of water and applied nutrients to the root zone. The middle of grove rows are allowed to grow over and are mowed as needed.

        Mechanical orange grove trimming.

        Sweet orange trees are trimmed with large mechanical hedgers after the seasons crop has been harvest. Trimmings are mulched into the middle of grove rows.

        Soil and Amendments

        Florida soil is primarily composed of a gray fine sand called ‘myakka’. Myakka is great for sweet orange growing as they require a well-drained soil with adequate depth avoiding a high water table. On average, Florida’s soil pH is 6.1, but locally the parent material determines the soil pH. For example, soil from under pine flatwoods is very acidic, but in parts of Central Florida and South Florida the high limestone bedrock (pH 7.8 to 8.1), which is composed of alkaline calcium carbonate, increases the soil pH. In a commercial sweet orange grove, testing the soil, typically in the fall, to adjust salinity and pH (between 6 and 7) is necessary for optimum growth; however, testing of the leaves provides more reliable information on nutrient deficiencies.,

        The nutrient limited soils of Florida need to be supplemented with the 14 elements that are needed for optimal orange growth are calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), zinc (Zn), manganese (Mn), boron (B), copper (Cu), molybdenum (Mo), chlorine (Cl), nickel (Ni), and the big three being nitrogen (N), phosphorus (P), and potassium (K). In Florida, fertilizer is usually applied 3 to 4 times per year, but use of biannual slow release dry fertilizer has recently become more economical. Fertilizer applied by fertigation has become more popular (typically nitrogen and potassium), but tractor and aerial foliar spraying is also commonly employed in Florida. Use of treated biosoilds can reduce potential contamination events.,

        Irrigation

        Gravity irrigation, also known as surface or flood irrigation, is when water is allowed to run through channels dug through the grove near the tree root zone. This method has become less popular due to the high water usage and need to maintain water channels every two to three years. Drip irrigation, allows the slow release of water through a hose network with releases near the tree root zone that can be laid on the surface or buried underground. This method is preferred when using reclaimed water as potential biological contamination does not come into contact with the fruit. Overhead sprinklers, require high pressure systems using uncontaminated water due to contact with the fruit. The most popular system used today in Florida is micro-irrigation systems that consist of a small, low pressure hose system with misters above the tree root zone.

        Freeze and Frost Protection

        A radiation frost occurs when an inversion layer develops on a clear night with calm winds and can damage flowers preventing fruit development. When the temperature falls below 28 degrees Fahrenheit for at least four hours fruit can experience freeze damage. Freeze damaged fruit can still be harvested for juicing. The greatest threat to orange groves occurs when temperatures drop to extreme lows (four hours at 20 degrees Fahrenheit) or just below freezing for extended periods of time (28 degrees Fahrenheit for 12 continuous hours) which causes ice formation in the tree tissue, potentially causing limb or tree death.

        Smudge pots, rarely used today, are filled with oil and burned throughout the orange groves to raise the temperature enough to prevent extensive crop damage. A piped fuel heater system with oil, natural gas, or propane can also be used. When a radiation frost with calm wind is predicted, windmills can be used to raise the temperature by disruption of an inversion layer. Helicopters have also be used for the same purpose.

        The most popular method for frost and freeze protection is irrigation. In the irrigation method, water is sprayed on or under the tree canopy. As the water cools latent energy is released as heat creating a micro-climate. Once the irrigation method is started, water spraying cannot be stopped until temperatures elevate to where the ice is loose and melting. This preventative method is typically used with under-canopy or micro-irrigation systems due to potential ice buildup and limb breakage when over-canopy sprinklers are used. Advantages of the irrigation method are in the cost savings as water is cheaper than fuel and the same system can be used for drought prevention, fertilizer application, and some pest control.

        Pest Management

        Orange drop as a result of citrus greening. Photograph by: Benjamin Klekamp

        The US Environmental Protection Agency sets Maximum Residue Levels for pesticides on fresh fruit. Over 90% of Florida oranges are grown to meet these standards even though the majority of Florida oranges are used for juice production

        In 2009, approximately 93 percent of Florida oranges were treated with at least one type of insecticide, but standard applications range from 6 to 12 times per year. Commonly used insecticides in Florida are abamectin, aldicarb, carbaryl, dimethoate, fenpropathrin, imidacloprid, and petroleum oil.

        Most common citrus diseases in Florida are citrus canker, citrus black spot, Phytophthora crown/foot/root rots, brown rot, greasy spot, melanose, postbloom fruit drop, and citrus scab. However, citrus greening is the most serious citrus disease in Florida and worldwide.

        Huanglongbing (Citrus Greening)

        Video: Fighting Citrus Greening Disease

        Huanglongbing (HLB), meaning “yellow shoot disease” and named for one of the disease manifestations, is suspected to be caused by the bacterium Candidatus liberibacter asiaticus. Having already impacted the citrus crops in Africa, Asia, Indian subcontinent, and Arabic peninsula, HLB was discovered in Florida in August 2005. HLB is of significant concern as it can impact all citrus. HLB is now in all Florida counties with commercial citrus production. Symptoms of HLB include yellowing of leaves, foliage drop, lopsided and bitter fruit, fruit drop, and tree stunting and death.

        Asian citrus psyllid on orange tree leaf with human fingertip in upper left.

        In 1998 the Asian citrus psyllid (Diaphorina citri Kuwayama), the vector of HLB, was identified in Florida. While unimposing at only 3 to 4 millimeters long, during its 15 to 47 day life cycle the female can lay upwards of 800 eggs. This equates to approximately 9 to 10 generations a year. HLB is transmitted when the psyllid (adult or nymph) feeds on a diseased tree. The disease needs a 21 day incubation period, but is then transmittable for life when the infected psyllid feeds on the leaves of an uninfected tree. Vertical transmission has not been indicated.

        Management of the HLB revolves around reducing psyllid populations, preventing their geographical spread, and ensuring groves receive proper nutrition. Nutrient foliar spraying has been used to keep diseased trees productive with some success. Currently no treatment is available to treat HLB infected trees. As efforts mount, public health professionals should stay informed of new methods used to combat HLB.

        Harvesting

        Harvest seasons subject to mother nature.

        Sweet oranges once picked do not ripen further; therefore, farmers must closely monitor their crop for peak maturity. An orange picked before maturity will tend to shrivel and are more likely to incur mechanical damage during processing. An orange picked after peak maturity will rapidly become soft and insipid. To assist in this delicate decision, farmers rely on visual inspection, taste testing, and laboratory analysis where a ‘soluble solid (or brix) / acid’ ratio is calculated. The minimum requirement for USDA Grade A canned orange juice is 10.5 to 1 brix/acid ratio.

        Hand picking oranges with field box below.

        Some farmers use an abscission agent (e.g., 5-chloro-3-methyl-5-nitro-1H-pyrazole (CMNP) to loosen the fruits attachment to the tree, which improves efficiency of both manual and mechanical harvesting.

        Goat loading field box onto open tractor-trailer.

        The majority of Florida oranges are picked by hand with workers climbing ladders with shoulder sacks that are then emptied in 900 pound field boxes. Field boxes are transported by a specialized truck called a ‘goat’ to an open tractor-trailer, which can hold roughly 45,000 pounds of oranges, for transport to the packing or processing facility.

        Video: Mechanical Harvesting for Orange Trees in Florida

        Finding enough workers to manually harvest the 146,600 acres of Florida orange groves in 2013 makes mechanical harvesting an attractive option. However, a significant upfront investment and concerns over tree damage to already very stressed orange trees in Florida from citrus greening has kept use of mechanical harvesting to a minimum.

        Processing, Packing, and Storage

        Fresh Oranges

        Video: Processing Florida Oranges for Fresh Consumption

        Oranges grown in a climate where the nights are not cool tend to produce oranges with some green color still in the rind even though the fruit is ripe. Some producers of oranges for fresh consumption will treat these oranges with ethylene gas. The treatment will not further ripen the orange, but will help de-green the fruit (i.e., remove the chlorophyll); however, this process may increase decay rates. A typical de-greening method may use 3-5 parts per million (ppm) ethylene under ideal conditions.

        Upon arrival at the packing plant, oranges are loaded onto conveyor belts and sent through soaking and pressure washing system. Washed oranges are then either mechanically or manually sorted to remove fruit with physical or ascetic defects. Rejected oranges are sent to be made into orange juice. A fungicide and edible polyethylene wax are then spayed onto the orange before final packaging for fresh consumption.

        Fresh oranges have an optimal holding temperature of 32 to 34 degrees Fahrenheit to maximize duration of shelf life. Moisture loss in the peel and pulp is the limiting factor in storage duration.

        Orange Juice

        Video: How Orange Juice is Made

        Oranges arriving at the processing facility are cleaned, washed, and juice extracted on high throughput mechanical squeezers. The orange peel is pressed to extract the oil, used later in processing for flavoring. The pulp is then filtered from the juice and both separately pasteurized. The pasteurized juice can be stored in large tanks to allow for blending of different varietals to create a consistent product. During final processing, if orange juice with pulp is desired, pulp is added back into the juice along with peel oil for flavoring. The juice is then aseptically filled into sterile containers.

        Unpasteurized orange juice undergoes a similar process through the extraction step, but receives little process beyond some filtering before final packaging and distribution. The final product must be continually refrigerated and typically has a short shelf-life.

        Frozen from Concentrate

        After unloading from the delivery tractor-trailer, the fruit is cleaned, washed, and juice extracted. Approximately 50% of the weight of the orange is juice. The peel of the orange is pressed for the oil, which will be added back later in the process to improve taste and smell of the frozen concentrate. The juice is filtered to remove seeds and large pieces of pulp, then pasteurized to inactivate enzymes and biological contaminates. A high heat vacuum evaporator is used to quickly remove excess water. The concentrate can be frozen in tanks until needed.

        During the final processing steps, the frozen concentrate is combined with pasteurized orange peel oil and juice to add flavor back that was taken out during the evaporation step. The final product is filled into sterile packaging. The minimum brix of the final product is 41.8 degrees, which will be diluted out to the approximate brix percent observed in freshly squeezed orange juice when the consumer adds the recommended quantity of water.

          Food Safety

          The peel of retail purchased fresh oranges, while used as a flavor enhancer in home cooking, are not usually consumed, but removed and discarded, in effect reducing the risk of illness from any potential exterior biological contamination. Public health professionals investigating an outbreak with possible fresh orange involvement should consider contamination by a food worker during hand slicing or peeling.

          Fresh and frozen from concentrate orange juice has been commonly thought to be safe for consumption solely based on a low pH; however, numerous outbreaks have shown that orange juice can harbor and transmit infectious pathogens.

          From 1922 through 2010, 14 outbreaks associated with consumption of orange juice were reported worldwide. Of these, 9 (64%) were from unpasteurized orange juice, 4 (29%) from frozen from concentrate, and 1 (7%) was unspecified. All reported outbreaks linked with unpasteurized orange juice were associated with either retail or food service establishments; whereas; outbreaks associated with consumption of frozen from concentrate orange juice were in hospitals (2, 50%), a hotel (1, 25%), and at a sporting event (1, 25%). Pathogens identified in unpasteurized orange juice outbreaks were predominately Salmonella (S. typhimurium, S. saintpaul, S. enteritidis, S. anatum, S. menchen, S. gaminara, S. hartford, S. rubislaw), but also included enterotoxigenic E. coli, Shigella flexneri, and a suspected virus. Frozen from concentrate orange juice contaminates identified in outbreaks include Salmonella typhi, Hepatitis A, and a suspected Norwalk-like virus.

          The inherent nature of manufacturing orange juice provides more opportunity for a single contaminated orange to cause an outbreak, compared to oranges consumed fresh, as the juice from thousands of oranges is combined before distribution and has more steps in the manufacturing process. Due to climatic variations that affect the fruit or manufacturer processing techniques, the pH of orange juice may rise above the normally observed range (3.6 to 4.3), which can permit pathogen growth. Also, some pathogens in orange juice, even at normally observed pH levels, will only be inhibited from reproductive growth and will remain infectious. As a result, a risk for illness from unpasteurized orange juice persists.

          The incorporation of pasteurization into the production process has made fresh and frozen from concentrate orange juice safe to consume. However, a risk remains in drinking unpasteurized orange juice as contamination can still occur by food handlers.

          A selection of outbreak reports associated with unpasteurized orange juice are provided below that highlight some of the principle food safety issues that have led to significant human illness.

          Article: Outbreak of Salmonella Serotype Hartford Infections Associated With Unpasteurized Orange Juice,1999

          Article: Major Outbreak of Hepatitis A Associated with Orange Juice among Tourists, Egypt, 2004

          Article: Multistate Outbreak of Salmonella Typhimurium and Saintpaul Infections Associated with Unpasteurized Orange Juice—United States, 2005

            Consumption

            To contribute to the Oranges Consumption section, please follow this link: https://fsi.colostate.edu/suggest-a-topic/

            Information on how to store oranges and keep them fresh can be found at FoodKeeper App.

            Nutrition

            Fresh sweet oranges are a low calorie (60 calories per 1 medium peeled orange), nutritious source of vitamin C (120% Daily Value (DV), fiber (12% DV), vitamin A (6% DV), and calcium (6% DV). The fresh fruit contains no saturated fats or cholesterol, but has high pectin concentrations, a beneficial dietary fiber. Orange juice is an excellent source for daily nutrition, however, consumers should read orange juice nutrition labels to observe a recommended severing size, as like all fruit juices, orange juice is calorie rich.

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