Temperature for tomato plants

Ministry of Agriculture, Food and Rural Affairs

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The Effect of Extreme Temperatures on the Tomato and Pepper Crop

Freezing and chilling injury in tomato and pepper plants

Although frost occurs, by definition, when the temperature drops to 0° C at 1.5 meters above the ground, this may or may not result in freeze damage to crops. The actual temperature at which freezing will occur depends on such factors as plant species and variety, plant vigor, soil conditions, surface cover, duration of the freezing temperature, thawing conditions, cloud cover, and wind conditions.

In tomato, freezing causes a darkening of the leaf or stem tissues. Damaged areas later wilt and turn brown. It may be difficult, initially, to determine whether the growing point has been killed and damage may become more evident on the day after the frost. Peppers are more sensitive than tomatoes to freezing temperatures and may be injured or killed by a light frost.

Tomato plants are also susceptible to chilling injury at temperatures between 0 and 5° C. Chilling can cause stunted growth, wilting, surface pitting or necrosis of foliage, and increased susceptibility to disease. Low soil temperatures also stunt plant growth and prevent root development. Temperatures below 10° C during flowering can interfere with pollination and result in catfacing of fruit.

Pepper plants experience chilling injury with prolonged temps of 0-10° C (32-50° F). Injury may show up as puckering of the leaves and stunting of the plant.

The effect of temperature on flowering in tomatoes and peppers

It is well known that flowering, pollination, and fruit set of tomatoes and peppers can be adversely affected by temperature extremes. The effect of various temperatures during flowering and fruit set of peppers and tomatoes is shown in Tables 1 and 2.

Table 1: The effect of temperature during flowering and fruit set of tomato


Effect on flowering, pollination, fruit set

Greater than 35° C (95° F)

Reduced fruit set

18.5 – 26.5° C (65-80° F)

Optimum for fruit set

Less than 13° C (55° F)

Misshapen or catfaced fruit may result

Less than 10° C (50° F)

Poor fruit set

Table 2: The effect of temperature during flowering and fruit set of pepper


Effect on flowering, pollination, fruit set

Greater than 32° C (90° ) day temp.

Pollen sterility occurs, flowers may drop

16° C (61 ° F)

Optimum for flowering and fruit set

Less than 15.5° C (60° F) or greater than 24° C (75° F) night temp.

Poor fruit set

What you may not think about when you see blossoms and fruit developing, is that low temperatures experienced by the plant weeks before flower buds were visible, can also affect flowering and fruit set.

A tomato plant which experiences temperatures below 15.5° C (60° F) for extended periods of time will begin to flower profusely. These flowers may remain open on the plant for several weeks, without fruit being formed. Larger flowers and increased branching of clusters can show up as a result of low temperatures experienced by the plant weeks before flower buds are visible.

Believe it or not…

Daytime temperatures of 15.5°C (60°F) with night-time temperatures of 10°C (50°F), four to five weeks before a tomato flower cluster blooms, may result in misshapen or catfaced fruit.


Night temperatures of 7-10°C (45-50°F) during pepper flower development can cause the fruit to be smaller than normal, or somewhat misshapen.

Chilling and freezing injury of tomato and pepper fruit

The fruit of warm season crops like tomato and pepper can be injured by low temperatures. Chilling injury occurs in tomato fruit if they experience temperatures of 10° C for longer than 14 days or temperatures of 5° C for more than 6 to 8 days. Tomato fruit exposed to a shorter duration of low temperatures may still be prone to storage problems, even if obvious injury did not occur in the field. Pepper fruit can be injured by prolonged temperatures below 8° C.

Frost injury is more severe than chilling injury. Tomato and pepper fruit are usually damaged between 0 and -1 ° C.


There is nothing like a fresh, sun-warmed tomato, so growing tomatoes is on everyone’s list. There are many kinds of tomatoes to consider, from beefsteak to cherry to heirloom varieties. There are also petite types bred specifically for hanging baskets. Tall and rangy cherry types can be trained up a trellis or over an arch.
Tomatoes grow best when the daytime temperature is between 65 and 85 degrees Fahrenheit. They stop growing above 95 degrees Fahrenheit. If nighttime temperatures are above 85 degrees Fahrenheit, the fruit will not turn red. Tomatoes need full sun and warm, well-drained soil.

©2007 Publications International, Ltd.
Stake tomatoes to help them grow.

Start tomatoes either by seed planted in the garden on the average date of last frost or from transplants set in the garden about a week after the average date of last frost. If you use transplants, either purchase them from a reputable nursery or garden center or start your own indoors six to eight weeks before the planting date. Plant transplants 18 to 36 inches apart, depending on whether you will stake or cage the plants or let them sprawl.
Set transplants out on a cloudy day or in the late afternoon. If the sun is very hot, protect the plants with a temporary shade of newspapers. Disturb the roots of transplants as little as possible. If the stems are leggy or crooked, set the plants deeply or in a trench. Side roots will develop along the stem, and the top will turn in the right direction.
Harvesting Tomatoes
The time from planting to harvest is 50 to 180 days from transplants, depending on the variety. The color when ripe depends on the variety. Ripe tomatoes should feel firm, neither squashy nor too hard.
Tomato Growing Tips
These tips will help you grow sweet, delicious tomatoes:

  • Prune tomato plants to direct maximum energy into tomato production. Choose your pruning plan based on what you want from your tomatoes. For larger and earlier (but fewer) tomatoes, remove any shoots that emerge on or beside the main stem, and tie the stem to a stake. For more tomatoes later, let plants bush out and support them in tomato cages. Pinch off any flowers that open before July 4.
  • Choose between determinate and indeterminate tomatoes according to the way you prefer to harvest. Determinate tomatoes (such as Celebrity) tend to stay compact and produce most of their tomatoes at about the same time. This is convenient for freezing, canning, and sauce making. Indeterminate tomatoes (such as Big Beef) keep growing and developing new tomatoes as they go. They produce a greater yield but spread it over a longer harvest period.
  • Dozens of different cultivars are in each class; there are plenty to pick from. You might have to check seed catalogs to find out whether a particular tomato is determinate or not.
  • Stake your tomato cages so a bumper crop won’t pull them over. Work a tall stake through the wire mesh near the perimeter of the cage, and stab or pound it to 8 inches deep in the ground. This will anchor the cage (and the plant inside) firmly despite the pull of strong winds and branchfuls of ripening tomatoes.

In the next section, we’ll talk about all of the different kinds of tomato types.
Want more information about tomatoes? Try:

  • Tomato Recipes: Cook with this delicious plant.
  • How to Remove Tomato Stains: Have a spill? Learn how to get tomato stains out of everything.
  • Vegetable Gardens: Grow a full harvest of great vegetables this year.
  • Gardening: We answer your questions about all things that come from the garden.


1. Q. Why do my pepper plants often bloom but fail to set fruit?

A. Peppers, like tomatoes, are sensitive to temperature. Most peppers will drop their blooms when daytime temperatures get much above 90 degrees F. in combination with night temperatures above 75 degrees F. They will also drop their blooms in the early spring if temperatures remain cool for extended periods. Hot peppers, such as jalapenos, withstand hot weather fairly well and can often produce fruit through the summer in most areas. Optimum temperatures fall between 70 degrees and 80 degrees F. for bell-type peppers and between 70 degrees and 85 degrees F. for hot varieties.

2. Q. If I remove the first few blooms on a pepper plant, will my overall production be increased?

A. Maybe. Occasionally, if a bell pepper plant sets the first bloom that flowers, the plant will be stunted as it matures that fruit. This is likely to happen if the plant is growing under marginal conditions which might include low fertility or perhaps low moisture. With the first bloom removed, the plant will grow larger before setting fruit which often does result in higher total yields. However, if the plant is grown under satisfactory cultural conditions removing the first bloom should not affect subsequent yield.

3. Q. If you plant hot peppers beside sweet peppers, will the sweet pepper plant produce hot fruit?

A. Absolutely not. Pepper flowers are self-pollinated, although occasionally cross-pollinate. However, the result of this crossing will appear only if seed is saved from this year’s crop and planted next year. It will not result in off-flavor or differences in fruit characteristics of this year’s crop.

4. Q. Can I cut back my spring planted pepper plants in late summer or early fall for increased production later?

A. Yes, although this is not a recommended practice. In the northern parts of the state spring-planted pepper plants can often be carried through to first killing frost without pruning. However, in southern parts, judiciously pruning the pepper plants and applying additional fertilizer as a sidedress application can prolong pepper production until the first killing frost. Pruning should not be severe in southern parts of the state as excess foliage removal can often result in burn, stunting or death of the plants.

5. Q. Is there any difference in taste or nutritive value between green peppers and those that mature and turn red?

A. Peppers that are allowed to mature and ripen entirely, from green to yellow to red, are higher in vitamin content, especially vitamin A. There is little difference in taste although there is a considerable difference in texture caused by the ripening process.

6. Q. How can you tell when jalapeno peppers are mature?

A. Jalapeno peppers are edible and flavorful at all stages of their growth. However, a connoisseur of jalapeno peppers can distinguish a definite flavor difference between a fully mature jalapeno and one harvested early. A fully mature jalapeno pepper, regardless of size, generally exhibits small cracks around the shoulders of the fruit. Often a darkened area on the fruit indicates maturity and the initial stages of a color change in the fruit.

7. Q. Can I save seed from this year’s pepper crop for planting in my next garden?

A. Yes. Peppers are self-pollinated and consequently will breed if seed is saved from this year’s garden for planting in next year’s garden. Although an occasional cross-pollination will occur, this is generally not a problem. Do not save seed from hybrid pepper plants as these will not breed true and will result in plants exhibiting characteristics different than the desired hybrid.

8. Q. The foliage on my pepper plants developed spots or lesions and the leaves have dropped off.

A. This could be a combination of three foliage diseases: Alternaria leaf spot, Cercospora leaf spot and bacterial leaf spot. In most cases, two or more of these occur simultaneously on the foliage. They can be controlled with foliar sprays using a combination of chlorothalanoil and Kocide or any other copper fungicide. Begin at the first sign of the disease and continue at 1- to 2- week intervals during the critical disease periods.

9. Q. The foliage and fruit of my pepper plants are distorted and small. The leaves have a mosaic pattern.

A. This could be one of five viruses that attack peppers in Texas. The best control is to buy healthy plants and to follow approved cultural practices and a good insecticide program. The viruses are transmitted by aphids. For this reason, it is important to control insects. Also, when a plant becomes infected with one of the viruses, remove the plant.

10. Q. After the recent rainfall, my plants wilted and died soon. The inner stems of the plants were dark.

A. This is Phytophthora stem rot. It is a soilborne fungus that attacks peppers. It is particularly severe in areas where water stands around the plant. Plant on a raised bed for optimal drainage.

11. Q. After a summer rain, my pepper plants died rapidly. I found a white growth at the base of the plant. Intermingled with this growth were small, round, bead-like structures the size of a pinhead.

A. This is southern blight, caused by a soilborne fungus. Crop rotation and deep burial of organic material will help control it. Do not allow leaves to collect around the base of the plant because the fungus will feed on them and later develop on the peppers.

12. Q. There are small wiggly trails all over the leaves of my pepper plants. What are these?

A. These trails are caused by leaf miners. Heavy infestations can defoliate plants and reduce yields. Control this pest by treating with diazinon or a recommended insecticide. Two or three applications at 5-7 day intervals may be necessary to achieve control. Use as directed on the label.

13. Q. We have just moved to this area and enjoy the Mexican food. What makes Mexican food so hot? Is it the pepper they add?

A. The cooks add pepper alright but not the black stuff you shake from a can – they add green peppers, Capsicum annum. These peppers contain a chemical named capsaicin. When you eat these “green bullets from hell” there’s a cellular response that releases neurotransmitters. These are proteins that mimic chemically the sensation of burning or pain. They go to the end plate of our sensory nerves and create the sensation of pain. The body’s response is to remove the chemical irritant by increasing heart rate to increase metabolism, by increasing salivation and increasing sweating. Your nose runs and the gastrointestinal tract goes to work in high gear to remove the irritant. You sweat to cool yourself.

The body’s strong reaction to capsaicin is why many people claim chili has medicinal properties. A paper by a New Mexico biologist noted that the death rate from heart disease in the state was about half the national rate. She also said the rate of heart disease among Hispanics and Indians was low. Presumed reason? They all eat lots of chile pepper and that reduces blood fat levels. Hot peppers are said to protect against blood clots that could cause thromboembolism.

So why do folks eat this hot food? When people eat hot chili the brain secretes endorphins, the opiate-like substances that block pain. Endorphins are produced when runners “hit the wall” and get their second wind. Who needs to jog and watch their diet? Just eat peppers and keep on burning!

14. Q. Can good pickled jalapenos be made from garden grown jalapeno peppers?

A. Yes, if you have a good recipe. Here is THE BEST:

Using fresh TAM Mild Jalapeno peppers, blanch peppers for 3 minutes in boiling water. To prevent collapsing, puncture each pepper. Add the following ingredients to a pint jar packed with the blanched peppers before cooling occurs.

1/4 medium-sized garlic clove 1/4 teaspoon of onion flakes 1 small or medium bay leaf 1/8 teaspoon of ground oregano 1/8 teaspoon of thyme leaf (not seed) 1/8 teaspoon of marjoram 1 tablespoon of vegetable oil (olive, refined sesame, corn)

Cover with boiling brine solution prepared as follows:
Mix together:

3 tablespoons sugar 9 tablespoons salt 2 pints water 2 pints vinegar (5 percent) Close the containers and process 10 minutes in boiling water, then cool.

Note: Jalapenos must be hot when brine solution is added. The addition of carrot slices adds color to the product.

15 Q: We have 2 bell pepper plants, in containers, that have until recently been very healthy and produced several beautiful peppers. Within the last week or two the peppers have developed small round tannish spots on the some of the fruit. The fruit were not fully developed, but we harvested then in order to save the fruit, if possible. In cleaning the fruit, the only damage is the small spot or two on the bottom of the peppers. I thought perhaps it was sunscald, but these plants have plenty of leaves. Could they be getting too much sun and would moving them to a shadier location help?

A: Tan or translucent spots on developing pepper fruit is DEFINITELY sunscald. All the young pepper has to be exposed to is a few minutes of direct sun during the hottest part of the day and that does it. Remember the last time you burned your body parts the first sun exposure of the spring?! The same situation! If you can see the pepper on the plant SO CAN THE SUN and it is not protected. A bacterial spot would be black so you can rule that out. You did right by removing the fruit; such removal may stimulate more foliage growth and subsequently more fruit protection.

16. Q. Do you have any information on the hot pepper used in Mexican dishes?

A. Is the Pope Catholic? Does a bear eat in the woods? OF COURSE, I have information on the pepper which made Mexican food famous! Peppers are hot, trendy items. Look at a recent crop of mail-order gift catalogs. Inside you can order pure silk chili pepper ties, sterling silver red or green chili pepper tie tacks; t-shirts, shorts, cotton caps blazing with red peppers or the red chili pepper string of Christmas lights. These gifts indicate the popularity of peppers. If you can’t grow peppers, the least you can do is wear one to show your support. The National Garden Bureau declares 1993, ‘The Year of the Pepper’ to encourage more folks to grow this New World native. With basic information, anyone in North America should be able to successfully grow pepper plants in pots or in the garden. Grow a hot or a sweet pepper for the flavor and satisfaction of saying “I grew it myself.”

The pepper, native to the tropics of Central and South America, has probably been cultivated for thousands of years. Archaeologists exploring prehistoric caves in Peru have found the remains of pepper seeds.

South America, Spain, England and the Caribbean all played roles in the introduction of the pepper to North America. Columbus explored the seas in search of a better trade route to the Indies. Dangerous, lengthy overland journeys made spices an expensive commodity for Europeans. When Columbus reached the Caribbean, he tasted a vegetable being grown by the Indians. Its sharp taste reminded him of the familiar black pepper from the East Indies and so he called this vegetable “pepper,” as we do to this day. However, Columbus was incorrect as the newly found vegetable was not the pepper of “salt and pepper” (Piper nigrum) but an entirely different genus, Capsicum.

He brought peppers back to Spain where they were considered an appealing alternative to the more traditional spice. The instant popularity of the vegetable is apparent from the comment of Peter Martyr, writing in 1493 that “…in the New World can be found plants hotter than pepper of Caucasus.” (He was referring to Piper nigrum.) From Spain the cultivation of the pepper soon spread to the rest of the continent and England. History does not tell us whether peppers reached North America via Europe or the Caribbean.

The first of the English immigrants to the colonies brought the seed of precious vegetables with them to plant in the New World. By the middle of the 18th century, North Americans could import many varieties of flowers and vegetables from England. John Randolph (1727-1784) of Williams-burg, Virginia wrote a treatise on vegetables grown in the New World colonies. In the essays, he referred to “Capsicum…it should be gathered before the pods grow hard for pickles.” Research conducted by the National Garden Bureau found that records kept at Mount Vernon indicate George Washington grew a “cayan” pepper.

While conducting research for this column an obvious nomenclature conflict became apparent. Some folks used ‘chili’ and others used ‘chile’ to describe a pepper. We reached several conclusions. Namely, that Chile is a country in South America. Seed companies use chili to designate a ‘ hot� pepper, and chile is generally an ingredient in ethnic foods. So if you purchase green ‘chili’ pepper seed, and grow the plants, you will harvest ‘chile’ peppers for ‘Chile rellenos’! Peppers are part of the Solanaceae or Nightshade family which contains over 2000 species of ornamental, medicinal and poisonous plants. This makes the pepper a close cousin to tomato, potato, tobacco, eggplant and petunia.

There are over 20 species of pepper but only one is commonly known to North American gardeners, Capsicum annuum. This species contains the pepper varieties widely cultivated in North America. Although Hortus lists five groups within the C. annuum species, we will refer to peppers as one of two kinds–sweet or hot.

Bell–This pepper is mostly blocky in shape with three or four lobes on the bottom of the pepper. For years, gardeners could choose only one color of bell, a green that matured to red, Through modern breeding efforts e can now grow bell peppers that mature to an artist’s palette of colors including red, yellow, orange, lavender, purple and chocolaTe. The bell peppers have a crisp, thick flesh and are suitable for eating fresh, or stuffing and baking.

Paprika–When dried and ground, this thin-walled pepper becomes the flavorful condiment paprika.

Pimiento–This heart-shaped pepper measures 3 1/2 by 4 1/2 inches. Fruits have very thick flesh. Strips of this fully mature, bright red, mild tasting pepper are found in stuffed greenolives.

Sweet Banana, Sweet Hungarian, Cubanelle–All of these are also referred to as sweet frying or pickling peppers. The shape is long, narrow tapering down to one, two or three lobes. These are thinner-walled than bells and Cubanelle has the thinnest walls of the three. They are usually picked when immature as a light yellow or green. Because they have less water content than bells, they are excellent choices for frying. ‘Sweet Banana’ is a variety that has withstood the test of time–it was a 1941 All- America Selections Winner. ‘Gypsy,’ a 1981 AAS Winner is early to mature–only 62 days and performs very well in cotainers as well as in regular gardens.

Sweet Cherry–Here is a pepper that looks like its name in that it is globe or cherry-shaped and about 1 1/2 inches across. This pepper is harvested when mature green to deep red and is generally used in processing as pickled.

Cayenne–This pepper is slim and tapered, ranging in length from 3 1/2 to 8 inches. Cayennes are often dried. The hybrid ‘Super Cayenee’ is a 1990 All American Selections Winner. It is very productive, early to mature and hot, hot, hot.

Red Chili–The small cone-shape peppers of this type are 1 to 3 inches long and have medium thick flesh. They are often used dried and ground in chili powder. ‘Super Chili,’ a 1988 AAS Winner is the first hybrid chili. The compact plants were bred for increased yields.

Green Chili–These are the long (7 to 8 inch) green, two celled mildly pungent Anaheim type peppers that are so flavorful in chile rellenos. They turn red at maturity but are nearly always harvested, green, roasted and peeled. They’re the kind you’ll find in the canned goods section of supermarkets labeled “Green Chile Peppers.”

Hungarian Yellow Wax (also called Hot Banana)–This pepper is pungent but still one of the more mild “hots.” It is 5 to 6 inches long and picked when an immature greenish yellow color but matures to orangish red. This type is good for pickling or canning.

Jalapeno–Jalapenos are the popular peppers used in many Mexican entrees. They are 2 1/2 to 3 1/2 inches long and have a thick-walled pungent flesh. They may be harvested when immatue green or mature red and are good for pickling or canning. There are many varieties of jalapeno peppers with varying degrees of pungency. It has been said that more than 200,000 pounds of jalapeno seed is planted in Mexico annually.

Red Cherry–This hot pepper is only 1 1/2 inches across and ahped like a cherry. It may be used fresh or pickled, primarily pickled.

Red Hot Peppers–There are other Capsicum annuum in the Longum Group that add distinct flavor to their native regional cuisines. These vary in plant and fruit size and shape. Smaller plants are attractive in patio containers and hanging baskets. These scorchers such as Chili Tepine, Chile Peguin, Tabasco, and Thai, mature red and zest-up foods. Many additional kinds are available. Small hot yellow peppers like Cascabella and Santa Fe Grande are used primarily for canning and pickling. There is the hot Serrano type that is popular in the Southwest. There is Habanero, said to be 50 times hotter than Jalapeno peppers.

Choose a sunny area of the garden as peppers need full sun to blossom and set fruit. Growth in full sun will result in a more productive plant. Select a spot protected from the wind as pepper plants have shallow, easily disturbed roots and brittle branches. A strong wind may break stems or completely uproot the plants.

The plant will perform best in well drained soil with adequate nutrition for plant growth. To insure adequate nutrition use fertilizes or work in well-rotted compost when preparing the garden soil in the spring.

A pepper plant does not take up a lot of garden space, at least when compared to vines like watermelon or pumpkin. Depending on the variety, most pepper plants will measure 2 to 3 feet tall. A half dozen plants should provide a family with a summer long crop of peppers. Gardeners with limited space can even grow peppers in containers. A large patio container will support one of the compact varieties such as ‘Gypsy.’

Many gardeners start seeds indoors early, then transplant to their garden, but seeds can be planted directly into prepared garden soil in long season areas. Sow pepper seed outdoors once the soil temperature has warmed to 75 degrees F. Place seed 1/4 to 1/4 inch deep, cover with finely textured soil and water gently but thoroughly. Peppers need moist conditions to germinate and are hungry for water during the seedling stage and throughout the growing season.

No time to sow and grow from seed? Head to the local nursery or garden center. You will find pepper plants that are just the right size for transplanting into the garden. Look for healthy plants that are green with with strong foliage. Yellowed leaves, spindly stems or sparse foliage indicate the plant is not thriving and probably will not perform well in your garden.

The same procedure and care are recommended for planting bedding plants or peppers home grown from seed. Wait until the weather has warmed to a daytime temperature of 65 to 70 degrees F. and nighttime temperature above 55 degrees F. To help warm the soil, black plastic may be placed on the ground. Slits can be made in the plastic to accommodate the plants.

Space plants about 2 feet apart. This distance will vary slightly depending on the variety. Rows should be spaced at least 2 feet apart. This will allow enough air circulation for the plants, permit easy cultivation and harvest. A time release fertilizer can be added to the soil now according to directions on the package. This fertilizer releases nutrients into the soil for about 120 days.

Peppers should grow rapidly given warm day and night temperatures. During this period of rapid growth be sure to provide adequate water and nutrients. Water the soil before plant foliage begins to droop or show signs of wilting. Take care to watch plants and look for any insect problems. Most locaTions in North America can grow any type of hot or bell pepper without any major problem.

If you notice blossoms dropping of your pepper plant, temperature may be the reason. The pepper is a warm season vegetable. It grows and produces fruit when the soil and air temperatures are warm. The temperature range for fruit set is quite narrow. When nighttime temperatures fall below 60 degrees F. or above 75 degrees F., blossoms are likely to drop and fruit will not set. Daytime temperatures above 90 degrees F. will also inhibit fruit set, but fruits will again begin to form when cooler daytime temperatures appear.

Gardeners may find that pests cause occasional problems. Early detection can prevent damage; inspect plants frequently for telltale signs of insects; presence. Large insects can often be removed from the plant. Any damaged leaves or stems should be removed and destroyed. Insects often make their homes among garden debris, quickly moving on to healthy plants. Remove debris from pruning or weeding once the yard chore is finished. If increasing insect populations appear, contact a garden center or a county Extension agent for information about insecticides to reduce insect populations.

Aphids are a major souce of pepper problems. They are very small insects (under 1/10 inch) found clustered on the undersides of leaves and on new growth. As they feed they suck plant juices; leaves become yellowed and distorted. They can sread all viruses, particularly Cucumber Mosaic Virus.

Thrips are another likely source of pepper problems. These small flying insects congregate by the undreds. Thrips are active insects, wounding plants to suck sap like aphids. Thrips damage leaves which generally curl upward into a “boat-shape.” These insects can infect peppers with Tomato Spotted Wilt Virus (TSWV).

While there are many viruses that can harm peppers, the following are the most prevalent in North America.

Tobacco Mosaic Virus–Leaves become yellow and a mosaic pattern can be seen on them. Eventually plants become stunted and fruit discolored. Because TMV can be found in tobacco, refrain from smoking near the plants. Do not handle plants after smoking tobacco. Many pepper varieties have resistance or tolerance to Tobacco Mosaic Virus.

Wilt diseases–These are caused by the fungi Verticilium and Fusarium present in the soil. The initial symptoms are wilting, upward curling of leaves, and yellowing. Eventually the stems and roots of the plant are affected. Verticilium wilt is more common in the western and northern parts of North America. Fusarium wilt is more likely to occur under conditions of wet soil and high temperatures.

Phytophthora root rot is caused by organisms found in heavy, poorly drained soils. These diseases are best prevented by good water management and crop rotation.

Cucumber Mosaic Virus–Plants are severely stunted with light green, leathery foliage. Leaves and fruit may develop yellow spots and rings. This virus is worldwide and can infect many food crops and weeds. Aphids can transmit CMV from weeds to vegetables and back to weeds.

Viruses and wilts are not very common in gardens. If a pepper plant appears to have the symptoms of a wilt or virus, the only action to take is to remove and destroy the plant.

There is no cure for a wilt or virus. Plants can be burned or put through a garbage disposal, if small, but do not allow the plant to be put into a community or home compost pile where the virus or wilt could infect other plants.

Peppers may be harvested and enjoyed when immature or mature. There is not a “best” time ti harvest, let personal taste preference be the guide. Remember that sweet peppers become sweeter as they mature and hot peppers come hotter.

To harvest, do not pull or tear a pepper from a plant. Peppers have shallow root systems and it doesn’t take too forceful a pull to dislodge the etire plant from the ground. Fruits of many varieties will easily snap off at the tem. With some varieties you will need to use a sharp knife or scissors to cut the fruit stem from the plant. Harvesting regularly will encourage the plant to keep blossoming and setting fruit, especially early in the growing season. If the temperature just drops belwo 32 degrees F. for a short time, covering the pepper plants will protec them from damaGe. At the end of the growing season such as September in Minneapolis, if there is a threat of killing frost, pick all fruit regardless of the size. This is the last harvest for the plants.

A cautionary note on preparing HOT peppers for storage or cooking. The “heat” in hot peppers is an oil called capsaicin that is contained in the placenta (membranes that join the seed to the fruit). This oil will easily get on hands and fingers during the cutting and cleaning process.

If you then rub your eyes, nose or mouth, the oils will be transferred to these areas with a distinctly painful burning. Wear plastic gloves while cutting the hot peppers to prevent any of the oil from covering your hands. Wash hands after preparing is finished. Do not rub your eyes!

Should you forget to use caution and end up with burning hands, gel from the leaf stem of an aloe vera plant offers immediate relief when applied to hands or other burning areas. Use the gel carefully. A 10 percent solution of chlorox will also neutralize.

The temperature of a ‘hot’ pepper can be controlled by using or excluding the seed san dplacenta of the pepper when cooking. If you wish a dish to be ‘hot’ include the hot pepper parts. If you want less heat, use the flesh only and dispose of the placenta and seeds.

Peppers may be stored fresh, frozen, dried or pickled. Peppers will continue to ripen after being picked. Store peppers at room temperature if you wish them to ripen. The ripening process will be slowed if the peppers are stored under cool conditions. If whole fresh peppers are placed in plastic wrap and stored in the refrigerator, they should keep for at least a week.

Peppers are among the easiest of vegetables to freeze. Most peppers such as sweet bell or jalapeno need not be cooked or blanched prior to freezing. Simply wash, slice open and remove seeds. They may be cut into strips, chopped or diced and placed in a freezer container. Once thawed the peppers will be soft but well-suited for use in soups, stews or cooked vegetable dishes.

Mature peppers may also be dried for long term storage. Make a Mexican ristra, a long string of dried chili peppers that can be hung on the wall for easy accessiblity as well as a colorful decoration. Use fresh chili peppers leaving the stems on. Make a small slit on each side of the pepper just below the stem. Insert a needle and thread through these slits and string the peppers together. Hang in a warm dry place. Use them in appropriate recipes or as a decoration. To dry “hot” peppers such as jalapeno, use waxed dental floss because the capsaicin oil dissolves thread.

Peppers are the right food for people seeking a healthy, nutritious diet. Low in calories, high in Vitamins A and C, peppers are also high in a very important mineral–potassium. One cup of raw sweet green peppers contains 22 calories. For comparison a cup of cucumber is 16, cottage cheese is 223 and whole orange is about 41 calories.

A red sweet or hot pepper contains about ten times more vitamin A and double the amount of Vitamin C than an immature green pepper. A 100 gram serving of red hot peppers eaten raw contains 369 milligrams of Vitamin C. The same serving size of sweet raw green pepper contains 128 milligrams, about one third less.

Whether green or red a pepper contains more Vitamin C than a whole orange which contains only about 50 milligrams. For potassium rich foods, an average banana contains 370 milligrams and a cup of green sweet pepper has 213 mg raw and 149 mg if boiled before being eaten.

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Tomato Temperature Tolerance: Best Growing Temp For Tomatoes

Tomatoes are the most popular home garden vegetable to grow. With a veritable plethora of tomato varieties, from heirloom to cherry, and every size and color imaginable, it’s no wonder. A suitable tomato plant can be found to grow in almost any climate and environment. The warmest growing temp for tomatoes and the lowest temperature to grow tomatoes are the eternal conundrum for the home gardener. Tomato temperature tolerance varies depending upon the cultivar, and there are many.

Tomato Plants and Temperature

Most tomatoes are warm season plants and should only be planted after the danger of frost has passed. Tomato temperature tolerance for extreme heat or cold snaps is of extreme importance to the development of blossoms and subsequent fruit set.

Blossom drop will occur in the spring if daytime temperatures are warm but night temps drop below 55 F. (13 C.). In the summer when temperatures soar over 90 F. (32 C.) with nights over 76 F. (24 C.); again, the tomato plant will suffer damage to immature fruit or loss of flowers.

Additionally, when nights become too warm, the pollen grains of the tomato flower begin to burst, thwarting pollination, hence no fruit set. This is doubly true when the air is saturated with relative humidity.

The growing temp for tomato seedlings should be maintained at constant temps of between 58-60 F. (14-16 C.), whether starting in the greenhouse or indoors, and then not transplanted until the last frost has passed.

Cold Hardy Tomatoes

There are specific tomato varietals bred for cold hardiness which will tolerate conditions at or below 55 degrees F. (13 C.). The best choices for colder climates are short to mid-season tomatoes. These tomatoes set fruit not only in cooler temps, but also reach maturity in the shortest number of days; around 52-70 days. One of the most popular is called Early Girl, but there are many different cold hardy varieties to choose from.

Some examples of hybrid tomatoes for cool climates are:

  • Celebrity
  • Golden Nugget
  • Husky Gold
  • Orange Pixie
  • Oregon Spring
  • Siletz

Heirlooms varieties include:

  • Bush Beefsteak
  • Galina
  • Glacier
  • Gregori’s Altai
  • Grushovka
  • Kimberly
  • Legend
  • Manitoba
  • New Yorker

These are just to name a few. A little research should turn up a dizzying list to choose from.

Heat Tolerant Tomato Varieties

Just as there are those of us who live in cooler climates, there are also those who live where temperature conditions run to the more extreme heat index. There are tomato varieties bred for those conditions as well.

Some examples of hybrids which are heat tolerant are:

  • Bella Rosa
  • Big Beef
  • Florida
  • Fourth of July
  • Grape
  • Heat Wave
  • Homestead
  • Manalucie
  • Mountain Crest
  • Porter
  • Sanibel
  • Solar Fire
  • Spitfire
  • Sunbeam
  • Sun Leaper
  • Sun Chaser
  • Sunmaster
  • Super Fantastic
  • Sweet 100

Heirlooms include:

  • Arkansas Traveler
  • Costoluto Genovese
  • Green Zebra
  • Quarter Century
  • Sioux
  • Super Sioux

Tomato Frost Protection

Besides planting cold hardy tomato varieties, some tomato frost protection may be provided by using plastic “mulches” or covering which will trap the heat to keep the fruit warm if temps drop below 55 F. (13 C.). Dark plastic coverings will raise the temps by 5-10 degrees while clear warm the tomatoes by up to 20 degrees. This may be just enough to save the tomato crop.

The answer is, of course, to remove all the tomatoes you can when chilly nighttime temperatures start to become the norm. But while just about any fruit with even the slightest hint of red should ripen off the vine, green tomatoes will only do so if they’re sufficiently mature. There are a couple of ways to tell if they’ve reached that point. The easiest is to assess the color. Fruit that has reached the “white stage,” when it turns from medium green to a very light (almost white) green, is mature enough to ripen off the vine.

If you’re not quite sure if the color is pale enough, though, here’s another option: Choose a fruit that’s representative of the remaining green fruits on the plant, then grab a knife and slice through it. If the seeds are contained in a gel sac, all of the similar tomatoes on that vine should ripen. (A gel sac refers to the jelly-like tissue that surrounds the seeds—it’s part of the delicious drippings when you slice a ripe tomato!) If no gel sac is present and you can slice through a seed, however, similar (and smaller) tomatoes on the plant will never turn red. (That doesn’t mean you have to give them up for lost, though—fry them, or use them in green tomato salsa, relish, jelly, or pie, or make pickles.)

So when temperatures start dipping below 50º F, leave the tomatoes on the vine if warmer days and nights are forecast. But if temperatures have started on a steady downward slide, go ahead and pick the mature green tomatoes and bring them indoors. Arrange them in a single layer in a shallow cardboard box, grouping them by color stage if you have more than one box’s worth. Lay a sheet of newspaper over the top and store at 55º to 70º F.

Check ripening tomatoes every few days, and cook or compost any that develop soft spots before ripening. Fully mature green tomatoes typically ripen in about two weeks at 70º F, or in about four weeks at 55º F. As tomatoes start to color, bring them somewhere you’ll see them regularly (like the kitchen windowsill or counter) and let them sit for a few more days to finish up. Tomatoes ripened this way may not taste quite the same as the ones you picked in the height of summer, but they’ll be head and shoulders above any you could buy at the supermarket.

Article written by Julie Martens.

Ideal Temperatures for Growing Tomatoes

The tomato is an import from a warmer climate to Britain so it’s no surprise that the ideal temperatures for growing tomatoes are higher than is usual outdoors here. Tomatoes can be grown successfully outdoors in the warmer parts of Britain, if the weather is kind.

Not too hot, not too cold!

‘Wild’ tomatoes used to be a common feature around sewerage works in the south of England. The reason being that the seed will pass through the gut and use our manure as fertiliser. Down in the south and south east it was just about warm enough for tomatoes to grow and fruit.

Tomato Varieties for Cooler Climates

Some varieties have been bred for cooler climates, notably Glacier and Sub Arctic Plenty.

Sub Arctic Plenty Tomato

The Sub Arctic Plenty tomato was developed after WW2 by the US military to supply troops stationed in Iceland with a fresh tomato despite a very challenging climate. Being able to thrive in cooler temperatures reduced greenhouse heating costs.

Glacier Tomato

Glacier is a Swedish bush (determinate) ultra-early variety that starts to produce ripe fruit in just 55 days from germination. Ideal for the short summer season enjoyed in much of Scandinavia.

In general though tomatoes require a temperature between 15ºC and 32ºC to survive.

Germination Temperatures for Tomatoes

The minimum temperature to germinate tomatoes is 15ºC but germination will be faster and more certain at 20ºC to 24ºC

Growing Temperatures for Tomatoes

Tomatoes can tolerate a night time temperature falling to 13.5ºC but if the daytime temperature falls below 15ºC for a week or more, growth will be stunted at best and crops reduced.

If night time temperatures drop below 13.5ºC, pollen fails to develop and flowers that open the following morning will not set fruit.

If growing in cloches or other shelter outdoors, the soil temperature should be over 12.5ºC although warmer is better.

The ideal temperature for tomatoes growth and fruit production ranges between 20ºC and 24ºC

Too Hot for Tomatoes!

It is common for home greenhouse growers to raise temperatures too high, especially in a hot summer. Just as we suffer when it’s too hot, so does the tomato plant. Energy that could be profitably going into fruit or growth is diverted into temperature control

Once temperatures rise above 27ºC plants really begin to suffer and above 32ºC fruit will fail to set.

In countries that enjoy a hot climate, tomatoes are often grown under shade for those reasons.

Further Information: Tomato Growing Guides

  • Grow Unusual Tomatoes!
  • Types of Tomatoes – An Introduction to Tomato Growing Part 1
  • Sowing and Starting off Tomatoes – Introduction to Tomato Growing Part 2
  • Growing Tomatoes in a Tomato Grow-house (Mini-Greenhouse)
  • Growing Tomatoes in a Greenhouse
  • Growing Tomatoes in the Greenhouse Border
  • Growing Tomatoes in Pots or Grow Bags in the Greenhouse
  • Growing Tomatoes by Ring Culture
  • Growing Tomatoes in Straw Bales
  • Growing Tomatoes Outdoors
  • Planting & Growing Tomatoes Outdoors
  • Growing Patio Tomatoes – Dwarf Bush Variety Patio Tomatoes
  • Water Requirements for Tomatoes
  • Ideal Temperatures for Growing Tomatoes
  • Removing Tomato Side Shoots (Suckers) & Stopping Tomatoes
  • Best Tomato Varieties – My Top Tasty Tomato Picks
  • Heirloom Tomatoes (Heritage Tomatoes)
  • Best Tomatoes for Greenhouse Growing
  • Tomato Troubles & Diseases | Causes & Cures of Tomato Problems
    • Tomato Blight – Blight Resistant Tomato Varieties
    • Tomato Blossom End Rot | Causes & Cures for Tomato Blossom End Rot
    • Tomatoes Magnesium Deficiency – Yellow Leaves, Epsom Salts
  • Raising Tomato Plants from Seed

Nothing says summer like a freshly picked, ripe tomato from the vine. However, in cold climate and short growing seasons it does not happen very often, if at all. Most tomato growers around here pick green tomatoes in the fall and after ripen them indoors. Our summer seem to be just too short and too cool to ripen tomatoes.

We have good news for you today: With these 9 simple tips you too can harvest ripe tomatoes in the summer.

Tomatoes are a summer crop. They die when freezing weather occurs. But they also do not like it cold, windy, and wet. In order to grow tomatoes and get them to ripen they need a warm, dry spot. However, with summer night temperatures dropping under 10C (50F) tomatoes will be shivering. What to do? Here are some simple tips for growing tomatoes in cold climate and harvest ripe tomatoes in the summer.

Note: To achieve ripe tomatoes in a greenhouse is much easier than it is outdoors, and I think it is the best way to go for us northern growers. Still, in this post I will concentrate on outdoor growing and just give some tips on greenhouse growing.

1. Choose an early tomato variety

Not all tomatoes are the same. Some ripen faster and tolerate cool weather better then others. Generally determinate or dwarf tomatoes are earlier and better suited for outdoor growing. Caseys heirloom tomatoes catalog has a guide to the best (non-cherry) tomatoes to grow outdoors in Calgary (zone 3a) and also a guide to the best tomatoes to grow in pots. You might find your favorite variety on that list.

Other seed suppliers have great tomatoes for outdoor short and cool season, too. Just make sure they are early. It is best to get seeds from local growers, or a climate similar to yours. Those tomato plants have already been adjusted to the weather, and will grow and produce better.

2. Start tomatoes about 6 – 8 weeks prior to planting them out

You want the seedling to be just about setting out buds. Not bloomed yet. In our area, our last frost date is May 26. Since tomatoes do not tolerate any frost, you might have to wait till June 1 to plant them outdoors. Start the seeds indoors end of March to mid April. If you have grow lights or a very sunny window, the seedlings will grow faster so plant them later. In most cases it does not work to start seedlings earlier to get ripe tomatoes earlier. If the seedling is overgrown, it will suffer, and you will get ripe tomatoes later, or not at all. Read all about starting tomatoes from seeds here. If you do have a greenhouse, and or use protection (see below) you might be able to plant them a few weeks earlier.

3. Choose a sheltered location

Location is everything when it comes to growing tomatoes. If you have a spot in your garden that is too hot for most crops, it might be just right for tomatoes. If you do not have a warm spot in your garden, but on your deck, tomatoes can be grown in pots or grow bags. We grow ours in grow bags on our driveway. The heat from the concrete and the black bags will help to keep the heat loving plants warm. See how to grow in grow bags.

Note, if you are in a warm climate, tomatoes might be to hot in containers on yurt driveway. We are speaking here about a cool climate.

4. Add manure to the soil while planting

Manure ha the tendency to warm up the soil. Especially horse manure is known for that. Just make sure the manure is composted. Later in the season, water with compost tea. The boost will help the plants to grow better and mature earlier.

5. Protect young tomato plants

You get what you pay for, or in this case what you invest in. To plant tomatoes in open field, and leave them to the elements, will not lead to early ripe tomatoes. Give them as much protection as you can give outdoors. I like the Plant Protection Blanket, it is light weighted and can be left on for days, as needed. You can cover a tomato bed with it, or wrap an individual plant.

Built a wind barrier for the tomatoes out of recycled windows. This simple frame works very well in creating an micro climate. You can also use a Kozy Coats Water Filled Garden Teepee, add water and place the filled teepees over the plants. The Kozy Coat becomes an igloo, keeping in the heat and warmth from the soil.

6. Add thermal mass

The Kozy Coat already works as protection and thermal mass, or you can simply put a milk jar filled with water next to the plant. Rocks work the same way, build a little wall behind your plants, the rocks will heat up during the day and give the heat back at night, giving some wind protection as well.

Thermal mass seems to be even more important in a greenhouse (See water tank in a greenhouse). A plastic covered greenhouse gives you only about 3 degrees at night, but heats up the place beyond comfortable during the day. The fluctuation is very hard on plants. Thermal mass helps to regulate it.

7. Hand pollinate

Pollinating tomato plants is very easy, just shake the plants, or the flower cluster a bit, that’s it. Sure, wind or insects can do it for you, but while waiting for them you might lose some precious ripening time.

8. Water with stagnant water

Watering plants with tap water may or may not harm beneficial bacteria in the soil, but it sure is to cold for heat loving plants. It is better to use stagnant water that is warmed up from the sun. That way the plants will not go into shock every time you water.

9. Prune your plant

Most determinate plants do not need pruning. Still, if you have very big tomato clusters, cut them back some, they will ripen faster. If the plant is indeterminate, definitely prune it back. See whether to prune or not to prune tomato plants. Outdoors you want to prune the plants even more than in a greenhouse. You will get less fruit, but they will be bigger and ripen faster. It’s the better choice.

Here you have it, 9 simple tips to grow tomatoes successfully in cold climate and harvest ripe tomatoes in the summer. The more protection, love, and care you give, the earlier the plant will grow and ripen. However, for growing ripe tomatoes around here some summers are better than others. If the weather is just too cool, and it snows in between, do not beat yourself up about it. Tomatoes do ripen nicely indoors. Happy tomato growing!

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