How to graft avocado

Avocado.

Excitement on the prospect of making a kill by growing avocados is not going away any time soon. Today, I explain the concept of grafting avocados.

Avocado tree grafting involves connecting the branch of an avocado cultivar (the scion) with the rootstock of a different tree. As the two grow together, a new tree is created. The closer the scion and the rootstock are to each other biologically, the better chance you have of successfully grafting them.

Grafting is necessary to obtain a large crop of top quality fruit and can speed up the process of fruit bearing. If you grow an avocado tree from an avocado seed, you’ll have to wait six years before you see any fruit. And even after the seedling grows, there is no certainty that the tree will be look like the parents or produce fruit of the same quality. That’s why it is not advisable to grow avocados by seed.

After removing the avocado seeds from a mature fruit, the seeds are washed and dried to remove the seed coat. Seeds can be germinated either in sawdust or sand, with careful attention to optimum moisture maintenance. Once, the germination starts the root and shoot are transplanted into a planting bag. Grafting starts about six weeks after transplanting.

Selecting grafting wood

Successful avocado propagation requires obtaining grafting wood from branches that have demonstrated high production of true-to type fruit, on healthy, vigorously growing trees. The best wood is on young trees, or older trees that have been cut back severely to force strong upright new growth.

Select graft wood that is firm and not rubbery or pithy. Each scion cut should have at least two, preferably three or four sound dormant buds. The best buds are large and plump, with a healthy green color. Undersized buds are less likely to survive and grow. However, extra-large buds and plump buds may be flower buds, which produce weaker vegetative shoots or none at all. Buds that are slim and elongate, often with tiny leaf like feathery tips, are not dormant; they will not store well and will take less successfully even when used fresh. Such immature buds have cambium that is more active and so might be considered better for propagation, but they are more vulnerable to desiccation.

How to graft

Grafting is a matter of precision. Position the branch section properly on the rootstock, such that the cambium on the branch and the cambium on the rootstock touch each other. If not, the graft is certain to fail.

Perhaps the most common method of grafting avocados is the cleft graft. Make a vertical split in the centre of the rootstock, then insert one or two branches (scions), with two or three buds, into the cambium layer of the rootstock. Place the rootstock in moist sphagnum moss. It will hold water but also allows for aeration. The temperature should be about 27oC, although the scion must remain cool. Create humidity to prevent drying of the graft union.

Avocado tree grafting is difficult. Even in ideal conditions, the odds of success are low, even for professionals.

Cut 6-inch lengths of healthy branch tips that each contain several buds, using a sharp knife. Take six to eight cuttings, wrap them in damp paper towels, and lay them in a bowl of ice to keep them cold and moist.

Make a T-shaped cut on a branch of the rootstock tree, about 12 inches from the trunk. The long part of the T should be about 1-inch long. Make a shorter, crossing cut that goes 1/3 of the way through the branch. Twist the knife slightly to pry the bark away from where the two cuts meet. Examine the bud sticks you cut and placed in the bowl. Choose a healthy bud, and cut it from the stick, beginning 1/2 inch below the bud and ending 3/4 inch beyond it. Bring the selected bud back to the rootstock. Slide the long end of the bud wood into the long part of the T-shaped cut, matching the bud to the horizontal cut in the T.

Wrap the budded graft with a rubber band, securing it above and below, but not actually on the bud. Remove the rubber bands when the bud unions have healed and buds begin to open, which should be within three to four weeks. As these new branches grow and mature, avocado fruit will be produced on them.

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Hass Avocado Tree

First called an “Alligator Pear”, the Avocado was used as a hedgerow windbreak for Citrus orchards in Southern California. The Hass Avocado was a chance seedling discovered by Mr. Rudolph Hass. Even though the plant was intended as rootstock for another popular variety of the time, his children so preferred the fruit that Rudolph patented it in 1935. We understand why!

The Hass produces outstanding fruit. Prized for its extraordinary, green-skinned, oval fruits which have a pebbly texture and present a pleasing appearance against the lush, glossy foliage. Hass Avocado, with its creamy slightly nutty flavor, is the standard that all Avocados are compared to today. This fruit will certainly delight your taste buds and be a delicious addition to a variety of dishes.

Try the latest trend… Avocado Toast! Sprinkle coarse ground pepper on top, spritz with Lemon juice and drizzle it with a bit of extra virgin olive oil. Mmm, delicious and filled with very healthy monounsaturated fats and fiber. Trying the popular Keto diet? Swap out for low carb bread. Either way, you’ll be eating clean.

Worldwide, Hass is the most popular commercially-grown avocado. Its durability in transport and reliable shelf life, make it a popular choice among growers and customers alike. While you can generally find Avocados at the grocery store, it’s such a treat to be able to grow your own. You’ll save money and gain a valuable, attractive plant for your backyard permaculture orchard.

When grown outside, Avocados are a beautiful large evergreen tree that can be pruned to any height. They do make a wonderful hedge plant which was their primary purpose in the early 1900’s.

#ProPlantTips Care

Hass Avocado trees are very sensitive to poor draining soils and care must be given when planting. If soil drainage is a concern, mound or build a raised bed at least 12 to 18 inches above the soil line and plant in the raised bed.

The Avocado’s root system is sensitive to being disturbed. Take care when transplanting not to damage or disrupt the root.

Avocados can be grown as a houseplant but will not produce fruit as an indoor/outdoor plant under normal circumstances. They can, however successfully produce fruit in containers in a heated greenhouse.

In Zone 9, this popular Avocado will require occasional protection from the cold, so a southwest-facing exposure with good winter air circulation is recommended.

In Zone 9, the Hass Avocado will produce without a pollinating companion. When grown in zones 10 and 11, the Hass Avocado needs a pollinating partner plant, such as the Bacon, Fuerte, Zutano and Sir Prize varieties.

The Hass is an ‘A’ type flower and ripens April – October and the other varieties listed have ‘B’ type flowers that ripen November – June. Both are outstanding flavored selections. Consider planting 2 different varieties for a year-round harvest at your fingertips.

Avocados are heavy feeding plants and are sensitive to micronutrients deficiencies. Avoid this by applying a balanced Organic Fertilizer such as Dr. Earth Life Organic and Natural All-Purpose Fertilizer quarterly. Remember to mulch your Hass Avocado 4 inches deep to the outside of the canopy and be careful not to overwater.

Harvesting and Storage

Hass Avocado is considered a black-skinned variety, though it is most often harvested green. This is a sharp contrast to the light green fruit within.

The best way to store Avocados is to leave them on the tree until needed. Hass will hang for months just waiting to be picked. Once picked, keep the fruit out to soften it. As the fruits ripen, their skin transitions to dark purple/black. Once soft they can be stored for a few extra days in the refrigerator.

Once planted the Hass Avocado will produce fruit in about 5 years. So be patient, this is a fruit worth waiting for and don’t wait too long to plant one. Order today!

A southern California staple, the Hass avocado tree is known far and wide for its fruit. And why wouldn’t it be? Flavorful and rich, these fruit trees produce fruit which is rich and flavorful, filled with healthy oils. It’s served sliced atop toast, rolled into sushi, and mashed to create guacamole for our Mexican fare.

But how did postman Rudolph Hass stumble across this gloriously-creamy, rich and decadent variety? Completely by accident, it turns out. The resulting fruit has swept the world, accounting to nearly 95% of US sales and 80% elsewhere.

Best of all, you can easily grow this tree yourself. A quick-bearing variety, you’ll often have produce by the tree’s second or third year. Let’s talk guac — or at least, how to grow your own Hass avocados!

This post is sponsored by Fast Growing Trees, who provided a Hass tree for this care guide.

Good Products For Avocado Growth:

  • Garden Safe Neem Oil Extract
  • Monterey Bacillus Thurigiensis
  • Tanglefoot Tangle-Trap Aerosol
  • Nature’s Good Guys Live Ladybugs

Quick Care Guide

A Hass avocado tree can be an amazing addition to your food garden. Source: 4nitsirk

Common Name(s): Hass avocado tree
Scientific Name Persea americana ‘Hass’
Family: Lauraceae
Zone: 9-11 outdoors, can be grown indoors in zones 4-11 in container
Height & Spread: Up to 7′ tall in container. Up to 20-30′ tall in ground at max height.
Light Full sun
Soil Extremely well-draining, loose, pH 6.5 or below
Water: Watering varies widely by season and size
Pests & Diseases: Various mites, thrips, mealybugs, ants, avocado worms. Also very susceptible to phytophthora rots, avocado black streak, some cankers.

The History Of Hass Avocado Trees

Avocados form on a long, thick stem. Source: frankenschulz

Alligator pear, aguacate, ahuacatl — these are all names for the fruit known as the avocado. Botanically, it’s known as Persea americana.

Prior to the market domination of the Hass cultivar, the most popular version was Fuerte. This milder, larger avocado descended from earlier versions cultivated in Central America and Mexico. And, as all delicious food does, it slowly spread to other regions. By the 1900’s, avocado was quite popular in the United States.

Enter Rudolph Hass. A postal worker who had a garden, he fell in love with avocados. Due to their expense, he sought seeds wherever he could find them. The seed which produced the tree that would eventually bear his name was purchased from a man named A. R. Rideout. Hass planted the seed in his yard in the late 1920’s, planning to graft Fuerte branches on it.

Every graft he attached failed. It wasn’t producing fruit as it was still young, and Hass threatened to cut it down to replace it. His children interceded, recommending he wait and see how it did on its own.

When it finally did produce fruit, it was bumpy and dark-colored, unlike the smooth skin of the Fuerte variety. The bumpy skin was much thicker than Fuerte’s, too. One of his children tasted the oily, creamy fruit, and immediately went in to present it to Dad to taste.

Begrudgingly, old man Hass agreed that this tasted a whole lot better than his planned Fuertes. The bumpy and thick skin also protected the tender, soft flesh inside, making it easier to ship and sell commercially.

Hass’ first sales of the fruit were at the post office where he sold avocados to coworkers. He later sold to a supermarket in Pasadena, CA, and local restaurants would sweep in and buy up the produce for full retail price.

He decided to patent his variety. Arrangements were made with a nursery to sell Fuerte rootstock with his grafted Hass branches on it. Unfortunately, he only earned $5000 from his patent over his lifetime, as people would purchase a tree and then graft to other trees.

Hass passed away in 1952, but his original mother tree survived until 2002 in front of his former La Habra Heights home. It eventually succumbed to phytophthora root rot. A sign is placed where the tree once stood, and La Habra Heights still celebrates this homegrown avocado variety during an annual festival.

Hass Avocado Tree Care

Avocado leaves are leathery with a very distinct vein pattern. Source: John and Anni

Avocados are not a difficult kind of tree to grow in warm regions. They are a bit finicky about their soil and moisture, but once established they can stubbornly cling to life. Let’s talk about the ideal planting and care for them!

Light & Temperature

As should be expected with most tree species, full sun’s essential for their growth. The more light hitting the canopy, the better they will do. A fully grown avocado tree should have plenty of light hitting the leaves.

The reason California is such a popular place for growing these plants is because of its weather. Avocados are not freeze hardy. An adult, fully grown tree can tolerate temps down to 28-32°. But younger plants are going to be much less tolerant of cold temperatures. Similarly, 100°+ temperatures reduce fruiting capability, and your plants will be at risk of sunburn if it’s too hot.

Optimal conditions for your hass avocado trees are areas which have full sun and which spend most of the year between 60-80° temperatures. Keep your seedlings sheltered from high wind.

Water & Humidity

Avocados are thirsty! When first planted, your tree may need to be watered as often as two to three times per week. Check the soil first, though. A good test is to scoop up a handful of soil and squeeze it. If it holds the impression of your fingers, it has enough water. Moisture in the top 2-4 inches is ideal, as the feeder roots are close to the surface.

Fully grown trees need more water, of course. A mature tree which is fruiting can easily suck up 20 gallons of water a day. Do not expect these to be drought tolerant. You’ll go through quite a lot of water for these tasty treats!

Keep a watchful eye on the soil moisture. You’ll need to develop a watering plan that suits your climate, and it will vary month by month. This can be tricky at first, but you will settle into a rhythm.

Ironically, despite their thirst, hass avocado trees don’t like having wet feet. Muddy, oversoggy conditions can promote root rot, and they’re quite susceptible to that. These do much better with slow drip irrigation than with a deluge.

Soil

Did I mention that this tree doesn’t like wet feet? The soil has a lot to do with that. Soil that’s enriched with a lot of compost and organic matter can hold moisture easily. If you’ve got good-quality soil, you may not need to water as often. In addition, avocados are sensitive to pH levels above 7, so you need to maintain pH no higher than 6.5.

The soil itself should be loose, friable, and in the sandy to loamy range. Avocados hate hard clay soil as it just doesn’t drain well. It’s also too tough for the tender feeder roots to permeate. The feeder roots are generally in the upper 6″ of soil around the tree.

Commercial growers often amend an area that’s 1′ deep by 3-5′ across heavily to improve it. They’ll then create a domed mound of soil, 2′ in height, over their amended area and plant in the center of that. This ensures good drainage and provides the right soil type.

Mulch in a 6″ deep layer with wood chips around your tree. Keep the mulch at least 6″ away from the trunk. This helps reduce moisture evaporation while preventing weed development.

Fertilizer

The branch structure of a mature avocado tree. Source: Prof. Mortel

There are a list of essential nutrients which avocados require for best growth. These should always be included in your fertilizer regimen.

  • Nitrogen: helps with growth and development
  • Potassium: helps with growth and fruit-bearing
  • Boron: helps with growth
  • Zinc: needed for fruiting

In addition to these, the following list is recommended but not as essential as the above:

  • Phosphorous: helps tree metabolism
  • Calcium: promotes good structure and healthy roots
  • Magnesium: required for photosynthesis
  • Iron: overall tree health
  • Manganese: overall tree health
  • Sulfur: lowers soil pH to maintain tree health

Fertilize in small doses over the entire growing season. The shallow roots can more readily absorb small doses.

Newly-planted trees don’t need much fertilizer, but in the first year applying about 1oz of nitrogen on a monthly basis from spring through fall is good. Don’t fertilize from November through February. In subsequent years, go by the trunk diameter. A total of a half pound of nitrogen per inch of trunk diameter per year is essential to good growth.

A professional soil test is recommended to determine annual amounts to apply of the other nutrients. Most home soil tests do not test for anything beyond NPK. But as a good rule of thumb, applying the first four annually will be required. The other nutrients should be tested for.

Propagation & Fruiting

Hass avocados are propagated by grafting only. They will not grow true from seed.

Unless you’re skilled at grafting, you’ll want to buy a grafted seedling from a reliable source like Fast Growing Trees. This ensures you’ve got a healthy young seedling to start with!

All avocados fall into one of two flower types: type A, and type B.

Hass are type A. They flower from February through May. When new flowers open the first time, they are female until they close that afternoon. When they reopen the following afternoon, it’s as pollen-producing male flowers. This means they’re somewhat self-pollinating.

Having a type B avocado nearby can increase the amount of pollination your tree will get, which increases crop size. Type B avocados produce female flowers in the afternoon, and the next morning the flowers are male. The timing is perfect for both types to cross-pollinate.

Pruning

Any new growth that appears below the graft joint should be removed when you notice it. This includes small branches or leaves. Growth below the graft is usually from the rootstock cultivar, and won’t form Hass produce.

Most pruning is for one of three purposes: to keep the trees at a certain height, to shape them, or to remove deadwood or diseased portions. Other pruning simply isn’t necessary.

When pruning for height, trim back only the tallest of the branch tips at any given time. This encourages the tree to grow wide rather than tall.

Most pruning is done while the tree is dormant in winter. As an evergreen, it never loses its leaves, but will still have a period of slow growth during the cold season. In warm climates like California, the earliest you should prune is November, but it’s best if done in late December to mid-January. Try not to prune after mid-February, as it should be coming out of dormancy then.

Troubleshooting

Early signs of a zinc deficiency are visible in a few of this tree’s leaves. Source: RobotSkirts

There are a few things to watch for. Let’s go over a quick list of the most common problems you’ll face.

Growing Problems

New growers often report that flowers fall off the tree without producing. This isn’t uncommon, and isn’t a danger.

Watch for yellow-veined leaves or paler leaves and poor growth as a symptom of nitrogen deficiencies. Zinc deficiencies cause yellow patches between veins on leaves, and the avocados may form as round ball-like produce.

Sunburn can cause the bark to peel away from the trunk and blackening of branches. Applying a whitewash to the trunk helps reflect the heat away. If you don’t have whitewash or a flat white latex paint, you can use white cardboard instead.

Pests

Many different mites can attack your hass avocado trees. The most common are the avocado mite, the persea mite, and the avocado brown mite. All of these respond well to treatment with neem oil.

A particular kind of thrips, avocado thrips are a relatively new pest that California growers are battling. At this time, the University of California recommends using environmental controls like beneficial insects to get rid of them. They generally cause cosmetic damage to your avocados rather than permanent tree damage.

Mealybugs and ants are an evil pairing for avocado growers. Getting rid of both simultaneously is wise. A wide band of sticky material around the trunk can prevent ants from climbing the tree. Ladybugs will then handle your mealybugs while they’re keeping your plant thrips-free.

Three different forms of avocado worm exist. These are all forms of leafrollers, and they go after your produce as well as the leaves. Bacillus thurigiensis is effective against them without causing damage to your beneficial insects.

Diseases

The most damaging fungus to an avocado is phytophthora. This in various forms can cause root rot, collar rot (a form of canker on the trunk) and fruit rot. In all cases, this spreads via watering. Keep trees and leaves dry. Ensure your soil drains extremely well without becoming muddy. Prevention is essential as there are no cures for phytophthora once established in your tree.

Avocado black streak is a canker-causing pathogen, but its cause is unknown. This creates black lesions on the trunk or branches which can crack and ooze sap. It appears most often after drought stress or exposure to excess salts, and can be fatal to the tree. Practice good irrigation with high-quality water.

Dothiorella canker is also common in Hass trees. These cankers are not black, but they also crack. The sap they exude dries into a white powder. Carefully scraping off the outer bark on the canker to remove it can help portions to heal. It can cause the tree to look sickly, but the trunk generally continues to survive.

Frequently Asked Questions

Not only are avocado trees productive, but they make excellent shade trees. Source: Travis S.

Q: How tall do Hass avocado trees grow?

A: Container-grown trees reach 5-7 feet. Those planted directly in the ground can reach 25-30 feet at max height. Many people opt to maintain their trees at about 15 feet tall.

Q: Are Hass avocado trees self pollinating?

A: Generally, yes. But as mentioned above, they cross-pollinate extremely well with a type B avocado. You don’t have to plant a second tree, but it will greatly increase your potential harvest.

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Lorin Nielsen
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Growing Fruit: Grafting Fruit Trees in the Home Orchard [fact sheet]

Grafting as a means of propagating fruit trees dates back several thousand years or more. Grafting is used for two principal reasons: most fruit trees don’t come true to seed (seeds from a McIntosh apple won’t grow into McIntosh trees) and cuttings don’t root easily. The technique of grafting is used to join a piece of vegetative wood (the scion) from a tree we wish to propagate to a rootstock.

Grafting is a fun way to get more enjoyment from your home orchard. You can use grafting to create trees with several varieties or to introduce new varieties into your home orchard. Grafting can also be used to change varieties of trees in your existing orchard (see Cleft Grafting, below).

Remember that you are almost always limited to grafting within a species… most apple varieties are compatible with each other as are most pears. You cannot graft an apple scion on a pear rootstock or vice versa.

Choice of rootstock

Today we have a wide range of rootstock choices that will produce trees of varying sizes, from full-size “standard” trees to true dwarfs (less than 10 feet tall at maturity). Different rootstocks vary not only in final tree size, but also in their winter hardiness, resistance to certain insects and diseases, and performance in various soil drainage types. Most dwarf rootstocks are also precocious, meaning that they bear fruit early in the tree’s life.

Rootstocks are propagated either by seed (for seedling rootstocks), or by the process of rooting cuttings, known as layering. Dwarfing rootstocks are usually rooted cuttings (Fig. 1). Several nurseries offer rootstocks in small quantities to home growers interested in grafting, and many nurseries offer fruit trees on a wide selection of rootstocks. Descriptions of some of the common apple rootstocks follow.


Figure 1: Rooted rootstock layer.

Seedling: Seedling rootstocks produce large trees that are very difficult to prune, harvest and manage for pests. Seedling rootstocks are not recommended for use in home gardens. Few home gardens have space for these large trees and the wait until first fruit will discourage most growers. In addition, pest control with these large trees is very difficult, usually requiring power equipment for spray application. However, these trees may have value when used for wildlife plantings. They cost less than trees with dwarfing rootstock and will grow rapidly, soon outgrowing the browse reach of deer if provided protection for just a few years

M.7 (Malling 7): M.7 was the dominant dwarfing rootstock in NH orchards for many years. It produces a semi-dwarf tree that reaches 15 feet in height and needs 15 feet of lateral space. Fruiting usually begins by the fifth year from planting. M.7 has some weaknesses, for example, it produces numerous root suckers that must be cut each year. On the positive side, M.7 is tolerant of collar rot, a major soil-borne disease of apple. Further, most varieties grafted on M.7 are very fruitful. Apple trees on M.7 should be staked to provide trunk support for the first four or five years.

M.26 (Malling 26): M.26 is an excellent apple rootstock for home gardens. It is precocious, often bearing some fruit as early as the year after planting. It is quite hardy and should do well in reasonably well-drained soils throughout NH. It produces very few root suckers. It needs support (preferably a stake that will last the life of the tree), and it produces fleshy root initials (called burr knots) on the above-ground portion of the rootstock. These burr knots are attractive to borers. M.26 is also susceptible to the bacterial disease fire blight. Plant the tree with the graft union only an inch or so above ground so less rootstock is exposed. Most varieties on M.26 can be planted at an 8-foot spacing.

Bud 9 (Budagovsky 9): This is the number one choice for NH home gardens if a fully dwarf tree is desired. This rootstock is productive, very precocious and when mature, trees on this rootstock stand only seven to eight feet tall. It should be staked to provide support for heavy crop loads. It is very hardy and should do well throughout NH. Apple trees on Bud 9 rootstock can be set at 7-foot spacing in the home orchard.

Selecting and Storing Scion Wood

Several nurseries sell scion wood. Other sources of unique varieties are commercial orchardists in NH and other home fruit growers. Scion wood is collected while trees are still dormant (usually in late February or March in NH). Scion wood should be straight and smooth and about pencil thickness (Fig. 2). Water sprouts that grow upright in the center tops of trees are ideal.


Figure 2: Scion wood.

Once cut, trim to 12-18” lengths, and place in a food-grade plastic bag. Place a damp paper towel or sphagnum moss in the bag to maintain moisture, seal, and place in the refrigerator until you are ready to graft, usually in mid- to late April.

Many newer varieties of apples and pears are patented. Propagation of patented varieties requires the permission of the patent holder along with a royalty fee for each new tree created.

Whip and Tongue or Bench Grafting

A technique commonly used for spring grafting is whip and tongue grafting, also known as bench grafting. Whip and tongue grafting can be used to add multiple varieties to an apple or pear tree already growing in the home orchard. Because this technique involves joining wood of equal or nearly equal diameter, generally about pencil thickness, whip and tongue grafting is done near the ends of branches.

To complete this graft, you will need a sharp knife and either grafting tape, masking tape, or a plastic strip to seal the graft. The first cut is a smooth cut approximately 1¼ to 1½ inch long, made with a single knife stroke (Fig. 3). This cut is made on the rootstock several inches above the top root. A matching cut is made on the bottom of a 5-6 inch long piece of scion wood.


Figure 3: The face cut should be made with a single stroke of the knife and come to a sharp point.

Figure 4: The tongue cut. A sharp knife is essential.

The second cut is a bit more difficult to make. Start by holding the wood as shown in Fig. 4. Starting at a point about ⅓ inch down from the tip of the cut surface, cut down into the center of the rootstock. This cut should be nearly parallel to the grain of the wood (Fig. 4). The bottom of the scion should be prepared in exactly the same fashion as the top of the rootstock.

Join the two prepared pieces, scion and rootstock (Fig. 5). Push the two together firmly to insure a snug fit and good contact. Finally, wrap the new graft union to protect tissue from drying. Masking tape is one option. Another is specially developed grafting tape. (Fig. 6). I prefer to use 1 inch wide strips of plastic cut from bread bags. Start below the newly formed union, stretching the plastic slightly as you wrap around and up over the union. This will help insure a moisture proof seal. Once the union is completely covered, tie the plastic strip off with a simple knot. A healed whip and tongue graft is shown in Fig. 7.


Figure 5: Scion and rootstock are joined to complete the graft.

Figure 6: The completed whip and tongue graft, sealed with grafting tape

Figure 7: A healed whip and tongue graft.

Newly grafted trees are set out in a nursery row to grow. The home vegetable garden is an ideal place to grow these trees out for a year or two until they are large enough to plant out in their permanent location. When planting grafted trees, be sure to set the graft union 2” (Fig. 8) or so above ground to ensure that the scion does not root.


Figure 8: Set trees so the graft union is a couple of inches above ground. If the scion (variety) roots, a large tree will result.

Cleft Grafting

Cleft grafting is a technique that produces a union between a large rootstock trunk or limb and a much smaller scion. Using this method, an older tree can be top-worked to change to a more desirable variety.

For this method, scion wood is collected and stored as described for whip and tongue grafting. Again, this grafting is done in April in NH.

The first step in cleft grafting is to prepare the older tree for top-working. The tree is cut off at a convenient height, usually 30 inches or so above ground (Fig. 9). Alternatively, individual branches within an older tree can be top-worked using this same technique.

Figure 9: Older apple tree, cut off about 30 inches above ground in preparation of cleft grafting.

Using a hammer and either a cleft grafting tool designed for this use or alternatively, a hatchet or chisel, a split or cleft is made in the wood (Fig. 10). This cleft is then held open using the end of the cleft grafting tool designed for that purpose, or a screw driver or similar tool (Fig. 11).

Figure 10: A cleft or split made using a hammer and cleft grafting tool.
Figure 11: The cleft is held open using the end of the cleft grafting tool designed for that purpose.

Once the stock is prepared, scions are cut and inserted to complete the graft. Two scions are prepared using pieces of pencil-thick, year old wood, approximately five to six inches long. The bottom of each scion is prepared by making a single, smooth, sloped cut on each side (Fig. 12).

Figure 12: Bottom of scions used for cleft grafting. The thicker side should be set to the outside of the stock.

These scions are set into the cleft, one on each side, positioned so that the cambial zones of the stock and scion ‘line up’ or touch (Figs. 13, 14 and 15). It is important to note that the bark of the stock is much thicker than that of the scion. The key is to line up the cambial zones, not the outside edge of the bark of each.

Figure 13: The knife point marks the cambial zone of the stock. It separates the bark from the hard wood inside.
Figure 14: Scion properly inserted into cleft in stock, assuring cambial zone contact.
Figure 15: A completed cleft graft – sealing with grafting compound is the next step.

If the stock is larger than four or five inches in diameter, I like to insert additional scions using a technique called inlay or bark grafting. Scions are prepared as shown in Fig. 16. Again, a four to five inch scion is used. A one-inch long cut is made up the middle of the scion from the bottom, and one side is removed. The other side is often tapered at the tip to make joining the scion to the stock easier.

Figure 16: A scion prepared for use in inlay or bark grafting.

Place the flat, cut surface of the scion flat against the stock and trace the sides into the bark of the scion with a knife. Then cut the bark in all the way to the hardwood using the tracings as a guide. Carefully peel back the bark and slide the scion in until it seats (Fig. 17). Using the bark flap as a cushion, nail the scion in place using a wide headed, wire nail (Fig. 18).

Figure 17: Scion seated in slot cut in bark of scion.
Figure 18: Scion nailed in place.

Insert scions up to every four inches in stock circumference. After a scion has been placed in each side of the cleft and inlay grafts have been added, all cut surfaces must be covered to prevent drying of sensitive cambial tissue. Use a commercially available grafting compound for this purpose. Check newly made grafts for several days to insure that no holes in the grafting compound have opened (Fig. 19).

Figure 19: Grafting compound must cover all cut surfaces of the stock and scion. Be sure to cover the cleft or split in its entirety, including on the side of the trunk.

What Comes Next?

If the grafts were made correctly, most will grow, some quite vigorously. These grafts will be brittle for a few years, so proper training is important.

The spring following grafting, select two successful grafts and join them together by wrapping the weaker one into the stronger one and tying it off with black plastic electrical tape. Over time, these wrapped shoots will graft together and create a very strong, natural bridge (Fig. 20).

Figure 20: Wrapping the two successfully greafted scions together creates a very strong structure.

Finally

Proper tools and supplies make the grafting job easier. There are several good grafting compounds on the market. Those that do not need heating are easier to use. While a hatchet can be used to make cleft grafts, a cleft grafting tool is relatively inexpensive and makes the job easier. Lastly, A sharp knife is your most important grafting tool and it makes sense to purchase a high quality one.

Download the Resource for the complete fact sheet and a printable version.

AVOCADO TREE

Botanical Name: Persea americana Description

A valuable commercial crop, the avocado tree thrives on rich well-drained soil. Due to flowering habits, avocado varieties are categorized into A and B groups. One variety is sufficient to produce adequate crops for the home garden, however by planting a tree from both groups the harvest will be much greater. Avocados begin to ripen once picked and may take up to 10 days to reach maturity.
Fruits are rich with oily flesh and are delicious eaten when fully ripe in sandwiches, salads. Guacamole is a famous blend of mashed avocado flesh, lemon or lime juice, onion, garlic, pepper and chili, it makes a very tasty dip.
Avocados are very fussy about their soil conditions and will not tolerate wet feet or heavy soils, it is essential to prepare the ground for an avocado well before planting. Young trees are susceptible to sunburn and damage from frost so a small shelter while they establish is a very good idea.
Advanced Information
DPI Avocado Information Kit
FAQ Avocado DPI QLD
Avocado Factsheet – Explains A & B types, Location & Planting, Pruning and much more.

Dwarf Avocado – Wurtz (A)

A small tree to about 4m popular for the back yard. A moderate cropper of medium sized rich, high quality fruit. Pear-shaped with dark green skin using Guatamalan rootstock. Aug – Oct Does best if grown with a B type pollinator.

Image Price Avail. Propagation Size Buy Options
$59.00 25 Grafted Pot: 4L
Height: 70-80cm
$79.00 0 Grafted Pot: 6L
Height: 90-100cm
*Nursery Pick up only too large to ship out Seeking Propagation Material

Dwarf Avocado – Lamb Hass (A)

Larger and rounder than most other avocado varieties. It has a very dark, almost black skin that only gets darker as it ripens. The flesh is a pale green colour with a creamier consistency than the more common Hass and it has a slightly nutty and creamy taste. It has a medium-sized seed. Lamb Hass is a smaller tree that bears more fruit and it matures later in the season than regular Hass avocados. The symmetrical fruit has pebbly skin with green flecks.

Image Price Avail. Propagation Size Buy Options
$59.00 11 Grafted Pot: 2L
Height: 70-80cm
$79.00 0 Grafted Pot: 4L
Height: 40-50cm

Avocado – Reed (A)

Large, round , thick skinned variety with a smooth, green skin. They have a mild to rich flavour and have a good storing ability once cut and placed in the fridge. They are also a great choice for using in salads as they tend not to go mushy as does a Hass when very ripe. H Aug – Dec

Image Price Avail. Propagation Size Buy Options
$59.00 8 Grafted Pot: 2L
Height: 80-90cm

Avocado – Bacon (B)

Upright vigorous avocado producing pear shaped fruit of medium quality. Most cold hardy variety, down to -5degC. Great for Victoria. H March – May

Image Price Avail. Propagation Size Buy Options
$59.00 7 Grafted Pot: 2L
Height: 50-60cm
$79.00 0 Grafted Pot: 4L
Height: 80-90cm
In Production

Avocado – Edranol (B)

The flesh is a buttery yellow creamy flesh with a delicious flavour. The skin is dark with bright green bumps and is rough textured. It grows best in coastal areas, in inland regions the skin turns russet brown.

Image Price Avail. Propagation Size Buy Options
$59.00 0 Grafted Pot: 2L
Height: 40-50cm
*Pollination beneficial A Group limited to one pre person due to demand In Production

Avocado – Reed Seedling

Seedling avocado we use as a rootstock. Very hardy strong growing seedling producing large fruit. Being a seedling expect a quick growing hardy tree, but don’t expect fruit for 5-10years.

Image Price Avail. Propagation Size Buy Options
$17.75 0 Seedling Pot: Olv.Tube
Height: 20-30cm
In Production
$19.75 0 Seedling Pot: 2L
Height: 70-80cm
In Production

Avocado – Fuerte (B)

Pear shaped fruit, small to medium in size with slightly rough, thin green skin. The flesh is of a buttery texture with excellent flavour. Vigorous spreading tree that bears biennially. Harvest April – June

Image Price Avail. Propagation Size Buy Options
$49.00 0 Grafted Pot: 4L
Height: 70-80cm
*Pollinators – A group beneficial In Production
$79.00 0 Grafted Pot: 6L
Height: 100-150cm
In Production

Avocado – Hass (A)

Most popular variety due to both its superior taste and excellent keeping qualities. Medium sized, pear-shaped fruit has an excellent creamy, flesh. The leathery rough dark-purple skin turns to black when ripe. H Aug-Dec

Image Price Avail. Propagation Size Buy Options
$49.00 0 Grafted Pot: 4L
Height: 70-80cm
*Pollination beneficial B Group limited to one pre person due to demand In Production
$79.00 0 Grafted Pot: 6L
Height: 90-100cm
Seeking Propagation Material

Avocado – Secondo (A) ®

Superior flavour, with smooth, creamy flesh and pear-shaped, green-skinned, fruits that are textured like hass. A vigorous variety that commences fruiting in its 2nd year. Self pollinating. H Jul – Dec This is a local selection with Hass and Sharwill as parents that was selected by Daleys and is proving an excellent backyard variety as well as being our nursery favourite.

Image Price Avail. Propagation Size Buy Options
$49.00 0 Grafted Pot: 4L
Height: 70-80cm
*Pollination beneficial B Group In Production
$79.00 0 Grafted Pot: 6L
Height: 90-100cm
*Nursery Pick up only In Production

Avocado – Sharwill (B)

A medium sized fruit with rough green skin closely resembling the Fuerte but slightly more oval in shape. The fruit has a rich flavour, good oil content and small seed. Sensitive to frost. H June, Aug The Sharwill represents up to 20% of all avocadoes grown in NSW, is a regular and moderate bearer with excellent quality fruit.

Image Price Avail. Propagation Size Buy Options
$49.00 0 Grafted Pot: 4L
Height: 70-80cm
*Pollination beneficial A Group limited to one pre person due to demand In Production
$99.00 0 Grafted Pot: 6L
Height: 100-150cm
Seeking Propagation Material

Avocado – Shepard (B)

A small to medium pear-shaped fruit with thick, green skin that peels easily. The fruit has an excellent flavour, medium oil content and does not turn brown when cut. H Feb/March The tree has a spreading habit and is a high yielding. It displays good resistance to frost and anthracnose.

Image Price Avail. Propagation Size Buy Options
$59.00 0 Grafted Pot: 4L
Height: 60-70cm
*Limited to one per person due to demand. Pollination beneficial A Group In Production
$79.00 0 Grafted Pot: 6L
Height: 90-100cm
Seeking Propagation Material

Dwarf Avocado – Pinkerton (A)

A rounded fruit with the later crop being more pear-shaped. The thick flesh has a smooth-texture, good flavour and high oil content. It shows some cold tolerance and bears consistently heavy crops. H June to August The fruit is medium sized with green leathery pliable skin and a small seed.

Image Price Avail. Propagation Size Buy Options
$59.00 23 Grafted Pot: 2L
Height: 90-100cm
$59.00 0 Grafted Pot: 4L
Height: –
*Pollination beneficial B Group limited to one pre person due to demand In Production

Avocado – Noela

Trial Product, Daley’s is currently trialling this product, but we will not have them available for sale in the foreseeable future. If you are interested in this item please request the email notification from this page, but at this stage we cannot give you an estimated time of availability. This variety produces huge oval fruits that can weight 1-2 kg. One fruit is large enough to feed the family. It has superb flavour and delicious smooth flesh. The selection was made from a seedling trees growing in Sunnybank, Qld.

Image Price Avail. Propagation Size Buy Options
$74.00 0 Grafted Pot: 4L
Height: 80-90cm
In Production

Avocado – Choquette (A)

A giant fruit weighting over 1kg. Good eating variety with smooth flesh and a creamy, rich flavour. The trees have good disease resistance, it is a cross between a Guatemalan and a West Indian type avocado and has smooth green skin when ripe. Daleys is starting production of these in spring 2018 and anticipate having trees for sale by spring 2020.

Image Price Avail. Propagation Size Buy Options
$49.00 0 Grafted Pot: 4L
Height: 80-90cm
In Production

Avocado – Hass Seedling

Seedling avocado selected from the Hass Variety. It will not grow true to type but a good choice if you wish to establish a strong growing tree. Try cincturing to force early cropping. more vigorous than a grafted variety

Image Price Avail. Propagation Size Buy Options
$19.75 0 Seedling Pot: 4L
Height: 70-80cm
Seeking Propagation Material
$19.75 0 Seedling Pot: Olv.Tube
Height: 40-50cm
Seeking Propagation Material

Avocado – Zutano (B)

Resembles the fuerte avocado with its pear shape and thin, glossy green skin, which remains green even when ripe, however its flesh is not as creamy or as rich in flavor. It has low oil but high water content, resulting in a slightly watery flavor, and has pale green flesh with a fibrous texture. Its mild flavor and problematic peeling makes it less desirable than other avocado varieties. The Zutano avocado tree grows upright, with a rounded shape and spreading branches.

Image Price Avail. Propagation Size Buy Options
$44.00 0 Grafted Pot: 4L
Height: 80-90cm
Seeking Propagation Material

Extra Images & Youtube Videos – Click to view full size

Plant Information or Specifications

Max Height (when in the ground with good conditions)

2-5m

Plants required to Pollinate

2 compatible plants (Pollination Required)
Learn about Pollination

Can it Handle Frosts?

Yes

Amount of leaves in Winter?

All Leaves (Evergreen)

Fruiting/Harvest Months

May, June, July, August, September, October, November, December,

Question & Answer

I live in Canberra and have a small back yard but I would like to grow one or two avocado trees with hass like fruits. Can you suggest a tree for me? Additionally do I need 2 trees to cross pollinate? From: YARRALUMLA ACT

Frost is your biggest concern in Canberra. Bacon is our most cold tolerant variety. Most avocadoes will crop by themselves but you will get much heavier crops with and A and B flowering types. Check out the Pollination Youtube on our Avocado page https://www.youtube.com/watch?v=Aahzspd1Yzk #CategoryAvocado1326

Customer Comments on Avocado Tree

Tree Information on growing, planting, pruning, maintenance, ripening, taste, pick or bonsai tips. But mainly how to grow a Avocado Tree Share Your Advice or ask questions on our Forum

Avocado

Has grows and yields well and stays on tree 12 mths if left, Fuerte grows but rarely sets fruit in windy weather, Bacon is self fertile in our area and yields well | Anthony Miceli – Mornington, VIC 20-Feb-2006

Avocado Tree

Hi, I just want to point that avocado is not native to South America. In fact its origin is North/Central America (Mexico and Guatemala). In Brazil people eat it in in halves sweetened with sugar and with a bit of lemon juice to add a sour taste. | Ricardo Pollastrini – João Pessoa – Brazil, PB 14-May-2007 Spread it on butterd toast with salt and pepper a very nice snack | Scott – Caboolture, QLD 21-Aug-2007 There is a problem with the guatemalan rootstock used at daleys. that being in frosty areas the scion lives (hass and fuerte), but the stock dies. If a mexican rootstock were used then im sure my plants would have lived. Till then ill grow in large tubs | Reville – Tabulam, NSW 18-Nov-2007 Mexican rootstock is more cold hardier, the rootstock we used has been used for 20 years in the hort industry. Fuerte and Hass are guatamalan hybrid avo varieties and they will not be much hardier than the guatamalan rootstock. | Greg Daley – Kyogle, NSW 20-Nov-2007 Best place to plant avocado trees are on hills. They like drainage. | Anna Quante – Valley Center, CA 06-May-2008 Avocado trees are not necessary Central American. I have seen them in the hills of Chile at latitude 40 south, where they are as tall as Blue Gums and get covered by snow. | Gabriel Salas – Maitland, NSW 07-May-2008 I live in geelong and want to know which avacado grows best if i chose to grow one | Keb Sheridan – Geelong, VIC 14-Jun-2008 Belinda, If you don’t get frosts then the Wurtz variety would be best although you still need a huge pot. If you do get frosts you should get a Bacon avocado. | Correy – Brisbane, QLD 03-Jul-2008 Denise, The smallest avocado tree is the Wurtz. It’s an ‘A’ type & should grow ok in Rocky. I’d put in a Hass ‘A’ & Sheppard ‘B’as well:-) | Brendan – Mackay, QLD 26-Oct-2008 Alice, The small hard lumps on the inside of the avocado skin means the tree is lacking Boron (Borax). Sprinkle ~1 handful to the sq. metre under the canopy & water in. Hope that helps. | Brendan – Mackay, Queensland 26-Oct-2008 What would be good to grow in adelaide? I just want one tree and to grow it in a pot. We have been having frosts the last couple of winters as the suburb we live in is on the Adelaide plains north of the city. | Desiann Dalton – Paralowie, Adelaide, SA 28-Oct-2008 Persea Americana I have just planted one in a fairly large pot…Here’s hoping…any tips? | Ann Turnbull – Perth, W.A 15-Nov-2008 Does anyone have experience with using a product called ‘Yates Anti Rot’ to prevent Phytophthora Cinnamomi root rot disease in avocados? I’d like to know if it’s suitable and does work. I’ve read it works if you spray the leaves? Help. | Brendan – Mackay, QLD 28-Dec-2008 I’ve heard about old-time gardeners up Nth Qld planting two avocado trees in the SAME hole. e.g., a Hass (type A) and a Shepard (type B) with excellent results. The person relating the story said ‘they bear like mad’. Maybe worth a try.? | Brendan – Mackay, Queensland 30-Dec-2008 Brendan thanks for you feed back I was told that you have to plant 2 trees so you have a m/f. is this correct. | Denise Hassam – Rockhampton, QLD 04-Jan-2009 Denice, we call avocado trees type ‘A’ and type ‘B’. Most avocado trees will bear by themselves, but you get more fruit if you plant BOTH a type ‘A’ and a type ‘B’. Just have a look at what Daleys have for sale, and you’ll find both type ‘A’ & ‘B’. | Brendan – Mackay, QLD 08-Jan-2009 Can anyone tell me if Avocado will grow as far north as Townsville? | Brad – Townsville, QLD 14-Feb-2009 Brad, the main variety for up north is Shepard, it’s a type ‘B’. I have Shepard, Hass type ‘A’, Edranol type ‘B’, & Reed Type ‘A’ growing here in Mackay. The Hass is struggling a bit, but the others are growing real well. Try Walden, Hazzard & Pinkerton. | Brendan – Mackay, Q 22-Feb-2009 Brad, Sheppard is the main variety for north. Try also Edranol, Fuerte, Hass, Pinkerton, Reed & Walden. | Brendan – Mackay,q., 4740 01-Mar-2009 Bob, Pinkerton is the one you’re after, it’s an ‘A’ type that can handle the cold to -5ºC. | Brendan – Mackay, Q., 4740 01-Mar-2009 I planted an avo pip.Its now about 5m 4yrs,no fruit.Is there away to tell variety from leaf? | Mike Mackenzie – Sydney, NSW 23-Mar-2009 Sorry Mike, don’t think so. Because yours is a seedling, it WILL be an ‘unknown’ variety. It could be a good avo, or may be useless, huge seed, thin flesh etc. To help it bear quicker, give it a bit of Phosphorous (P) and Potassium (K), then mulch thickly | Brendan – Mackay, QLD 19-Apr-2009 In frosty areas try planting under a well established buddleia the droopping branches protect the seedling when young and grow up through the bush..thusfar is working exceptionally well | Kim Harvie – Bundarra, NSW 05-May-2009 Hi Rose, you won’t get a Fuerte tree from a Fuerte seed. Read my info to Mike above. You can grow the Fuerte pip, then graft a Fuerte scion onto that, if you want a Fuerte tree. | Brendan – Mackay, QLD 05-Jul-2009 I planted a pit from an avocado of Puerto Rico. It is fifteen feet tall is over20 years old look beautiful but no fruit | Antonio Diaz – Madrid , SPAIN 14-Oct-2009 Hi Antonio, cut it back by 1/3rd, give it some Sulphate of Potash, Blood & Bone, gypsum, epsom salts & zinc, mulch well to the dripline plus a bit more (keep the mulch away from the trunk) | Brendan – Mackay, , QLD. 28-Oct-2009 Hi. I recently bought a ‘lamb hass’. It’s about 1m tall, in a pot. Will it bear fruit on it’s own? Or do I need to get a partner for it? (I’m assuming the lamb hass is an ‘A’, just like the regular hass). Thanks! | Tanya K. – , 10-Dec-2009 Bought Bacon (B) in October. Planted in a larger pot with good potting mix and good drainage. But the tips are browning. I dont over water or dont let it dry out. Any ideas how to get it back? Thnks | Nil – Melbourne, VIC 11-Dec-2009 Can anyone give advice on the best avocado to grow in north-west Sydney? I have deep, well-drained soil and north-west aspect. A few light frosts in winter. | Simon Ward – Rouse Hill, NSW 17-Jan-2010 Old avocado tree and no fruits? Hit and shake its trunk at night time and (talk to it and explain :-)), observe and wait. My neighbour got fruits that way.Unbelievable! But true. | L Villar – Bradenton, FL 26-Jan-2010 Alice – Hard bits in Avo. Have bought a property with avos that received lots of NPK fertiliser. The fruit had lots of hard bits. We stopped NPK and used more natural fertilisers (or none) and the hard bits disappeared. Never had any in the last 5 years | Adrian Hofmann – Springbrook, QLD 10-Feb-2010 I grew avos in south africa,in a sub tropical climate.used to dig in iron fillings once a year.had to support branches to prevent breakage.seems to make the trees bear in abundance | Shaun Porter – Perth, WA 27-Jan-2011 Seedlings or grafted – Avocado trees die quickly due to root rot, even in sandy soils | Carl Ramirez – Kensington, NSW 15-Feb-2011 Have about 7 seedling trees that all started bearing in their 3rd year. I have access to a white flesh variety, very creamy texture. Will swap seed for a yellow flesh type which is sweet (which I tasted once at a Healthy Soil weekend near Mareeba). | Sandi Feller – Atherton Tablelands , QLD 18-May-2011 Commercial growers withhold water to stress their trees, which makes them set heaps of fruit. One year one of my trees looked like it was dying -not many leaves, but masses of fruit. After a good wet, lots of lush leaves, but not much fruit. | Sandi Feller – Ravenshoe, N QLD 18-May-2011

Avocado – Pinkerton (A)

We had a pinkerton & a haas in Adelaide hills, the pinkerton produced masses of fruit, would recommend it | Helen Western – Blackwood, SA 16-Sep-2011

Avocado – Wurtz (A)

My poor Wurtz is now going really well. It spent a year in a pot, then I planted on a solid clay slope by mounding the soil around it. It was eaten almost to the ground by a roo. But now has small fruit on it and is looking really strong. | Gary – Uki, NSW 17-Oct-2011 Planted 1 month ago. Dug a hole 1 m in diameter and 70 cm deep in a sunny position. Soil was rocky and clay. Filled hole with an equal mix of cow, sheep, horse compost (not fresh manure), mixed in handful of gypsum to sweeten. Top growth in 1 mth. | I. Birkholz – Ormeau 4208, QLD 17-Jan-2012 I just moved to Young NSW and i want to plant an avocado tree, wich 1 will be best because it gets cold here and frosty | Maria Wakeford – Young, NSW 13-Nov-2013 If growing from seed tip at about 1.5 M and every tear till mature. This will stop from becoming leggy and making fruit inaccessible. | Ken Ford – Larnook, NSW 11-Jun-2014 Tried striking seeds in water but found in good quality potting mix with pure cow manure worked better would like some b seeds if anyone hase some will pay freight thanks | Neil Robinson – Sarina, QUEEN 11-Mar-2015 They seem to love being fed cow poop & plenty of organic compost. I’ve had mine for 12 months & it’s going great guns in a pot. I have flowers at the moment but believe it’s still too young for fruit this year. | Wendy Archinal – Casino, NSW 15-Sep-2018 Did the mistake potting in big pot lost a few plants before finding out to use slightly bigger pots till you get to a huge one then still have to trim roots and repot since then not one loss (cross fingers) | Yan Koek – Macquarie Fields , NSW 31-Oct-2019

Customer Feedback
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For Further Information:

QLD DPI Information Avocado
Blog: Secondo Avocado Tree
Blog: Dwarf Avocado Trees – Fuss Pots
Avocado Maintenance Schedule
California Rare Fruit Growers
NSW DPI, AGFACTS – avocado Growing
NSW DPI , AGFACTS – avocado pests & diseases

Master Grafter

So why do you graft?

PETER YOUNG: Well Jerry, the reason…the main reason we graft is to reproduce an identical individual. If we just plant a seed, if that’s from sexual reproduction and the seedlings we grow are all different – just as we are different. So what we do is we plant a seed of the unknown seedling and then we go to a known mother tree and we take a cutting off it and we graft it onto the unknown seedling and we end up with the variety that we want. Here we have a graft avocado, so…and this happens to be the ‘fuerte’ variety or ‘fuertie’ variety. It could even be a ‘hass’, but the most important thing is, the unknown is changed into something we know.

JERRY COLEBY-WILLIAMS: So this rootstock has special qualities that maybe protect it against disease and the topstock provides the fruit that you really want to enjoy?

PETER YOUNG: Correct.

JERRY COLEBY-WILLIAMS: And when it comes down to grafting, you can’t just put anything on top of an avocado rootstock. It’s got to be something compatible?

PETER YOUNG: That’s correct. It’s got to be usually within the same genus…certainly within the same family.

JERRY COLEBY-WILLIAMS: The nursery uses a range of different grafting techniques.

PETER YOUNG: First of all, we’re going to demonstrate the ‘whip graft’. We’ve got Mike along here who’s one of our most experienced grafters.

First he makes a single cut on the rootstock and then he’ll do exactly the same thing on the piece of grafting material which we’ve collected from a ‘Pinks Mammoth’ Custard Apple Tree….puts the two together…..

JERRY COLEBY-WILLIAMS: And that’s a very close match isn’t it? They’re almost exactly the same size.

PETER YOUNG: Yep. It’s got to be very, very close. Looks really good. And then he’ll tie it up with some plastic tape. You must remove this tape afterwards, otherwise it will actually cut the rootstock in half….and that’s tied up firmly.

JERRY COLEBY-WILLIAMS: Now that keeps it together while it’s healing…

PETER YOUNG: It does….that’s right.

JERRY COLEBY-WILLIAMS: ….but it also keeps moisture in so it doesn’t dry out. So what type of graft are we going to see next?

PETER YOUNG: Terminal side graft. We often call it the ‘Asian’ graft and it’s one that we can use on evergreens like mangoes and avocados. You could use it on hibiscus, roses…you know, pretty well anything that’s evergreen.

We make a long cut on the grafting piece…turn it over and put a chisel point on the back, then we just split the rootstock the thickness of the prepared grafting piece, so we’re putting it on the side, not down the middle and this is…hence it’s on the top, which is terminal and on the side, hence the name ‘terminal side graft.’

We’re keeping some leaves on the rootstock. This is important to have some solar panels on the rootstock to feed the root system during the grafting operation until the graft grows away.

JERRY COLEBY-WILLIAMS: Traditionally, the grafted plants that you’ll find in any nursery, have only one graft which is the topstock – the fruiting or flowering part. The bottom part of the plant, the rootstock, is always seed grown and that makes it variable and a bit unpredictable. Birdwood is pioneering a new grafting technique called ‘Clonal Rootstock Production.’ They’re the only nursery in Australia doing this at the moment and what that means is that the rootstock is cloned – just like the topstock.

PETER YOUNG: First we start off with a nurse seed and this is the sexual seed. We plant an avocado seed. This is going to power the whole cloning process. When the shoot gets to around about 150 to 200 millimetres long, we graft it with the clonal rootstock graft. This has been selected for its tolerance against phytophthora root rot disease and also waterlogging.

So what we do is, we take a graft off the rootstock tree – we graft it onto the unknown sexual seedling and here, we’re going to be producing roots – so this is root cloning.

JERRY COLEBY-WILLIAMS: Ok, so now this has been grown in the dark?

PETER YOUNG: It has. Put it into a dark room.

JERRY COLEBY-WILLIAMS: And that helps the roots to be produced along the stem?

PETER YOUNG: Yeah, the chlorophyll inhibits rooting, so if we get rid of the chlorophyll, we get roots very easily on the clonal rootstock.

JERRY COLEBY-WILLIAMS: Ok and now this little thing here…?

PETER YOUNG: Eventually we want the nurse seed at the bottom that’s powering the whole process to die, so we put this little ring on to cut it off and that usually happens within 4 to 8 months.

JERRY COLEBY-WILLIAMS: The cloned rootstock then takes over with its own roots.

PETER YOUNG: So we’ve had our first graft at this for the clone roots. The second graft is for the fruit….and there’s the finished product on the end. That one there is around about 9 months.

JERRY COLEBY-WILLIAMS: So the result is a completely reliable, cloned, double-grafted avocado tree.

Grafting is an ancient art and here at Birdwood, Peter has found new ways that will benefit gardeners – wherever they may live.

After such a long time in the business, what keeps you happy coming into work on a Monday morning?

PETER YOUNG: I guess it’s the plant passion that keeps me going. Once you get chlorophyll into your veins, you just can’t get rid of it.

COSTA GEORGIADIS: It’s hard to believe that Antarctica is the driest continent on earth and that Casey Station, one of Australia’s bases there, has a thriving vegie patch.

New avocado rootstocks are high-performing and disease-tolerant

Greg Douhan, an assistant professor of plant pathology and microbiology at UC Riverside, examines an avocado plant in the greenhouse. Credit: UCR Strategic Communications

Avocado, a significant fruit crop grown in many tropical and subtropical parts of the world, is threatened by Phytophthora root rot (PRR), a disease that has already eliminated commercial avocado production in many areas in Latin America and crippled production in Australia and South Africa. Just in California the disease is estimated to cost avocado growers approximately $30-40 million a year in production losses.

Research on developing PRR-tolerant rootstocks to manage the disease has been a major focus of avocado research at the University of California, Riverside since the 1950s. The latest research now comes from a team that has released three rootstocks, available for commercial propagation by nurseries, that demonstrate superior tolerance to PRR.

The research, scheduled to appear soon in the journal HortScience, describes the three avocado root-rot-tolerant varieties: Zentmyer, Steddom, and Uzi.

Zentmyer is an extremely vigorous and highly durable variety that is PRR-tolerant under most conditions. But it is not recommended for locations, such as some parts of California, where salt is a problem and often does not yield consistently under non-root-rot condition. Steddom has both a high PRR-tolerance and good salt tolerance. Uzi is highly tolerant to PRR, and its yields are high and usually consistent.

The Zentmyer rootstock is named after George Zentmyer, a pioneer avocado pathologist at UC Riverside and a collector of avocado germplasm (hereditary material). Steddom is named after a former graduate student at UCR. Uzi is named after an Israeli scientist.

This photo shows a dying Hass avocado scion on a rootstock that is not tolerant to root rot. Credit: Douhan lab, UC Riverside

“With the release of these high-performing rootstocks, avocado growers worldwide will have more options in choosing PRR-tolerant rootstocks to determine which ones perform better under their own growing conditions,” said Greg W. Douhan, an assistant professor of plant pathology and microbiology, who led the research.

A rootstock is the part of the plant that produces the root system. For many fruit trees it is often genetically different than the scion — the top portion of the plant — that is grafted to the rootstock. The scion gives rise to leaves, stems, flowers, and fruit.

Commercial avocado trees are propagated by grafting scions of desirable cultivars onto various rootstocks with the most popular avocado cultivar being the Hass avocado. While avocados can be grown from seeds, their fruit quality and yield potential can vary dramatically. Therefore, it is more advantageous for avocado growers to have both a scion and rootstock that has the most desirable characteristics, enabling the best “plants” to be grown for profitability and consumption.

Prior to the development of specific avocado rootstocks, nurseries produced avocado trees, such as the Hass cultivar, on arbitrary avocado rootstocks, knowing almost nothing about the rootstocks’ genetics. Because different rootstocks were used, it led often to orchards producing avocados of varying quality.

Brandon McKee, a staff research associate in plant pathology and microbiology, examines root rot symptoms in an avocado plant. Credit: Douhan lab, UC Riverside

The three new rootstocks were initially selected for PRR-tolerance based on approximately two years of screening under greenhouse conditions at UCR. Eventually, the three varieties were tested throughout several locations in California over many years to determine their viability for public release.

The UCR Office of Technology Commercialization is pursuing licensees for all three new avocado rootstocks for their successful commercialization, and will give preference to California avocado nurseries and growers.

The PRR-causing pathogen (Phytophthora cinnamomi) was first identified as causing PRR in avocado in Puerto Rico in 1928. It was eventually determined in 1942 to be responsible for a general decline of avocado trees reported in California since the late 1920s and 1930s. When PRR is controlled, avocado yields, growth, and fruit quality increase dramatically, resulting in increased profitability for growers.

“The ultimate long-term objective of the UCR avocado research program is to find a truly PRR-resistant rootstock for avocado,” said Douhan, who joined UCR in 2005. “This objective has not yet been realized, but we have been making good progress and our germplasm foundation is continuing to broaden.”

Douhan is confident that with the use of more modern molecular tools research will proceed faster in understanding many aspects of avocado genetics and the genomic diversity associated with PRR and other important agronomic traits.

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Early action tipped to save tonnes of Aussie avocados Provided by University of California – Riverside Citation: New avocado rootstocks are high-performing and disease-tolerant (2012, April 27) retrieved 1 February 2020 from https://phys.org/news/2012-04-avocado-rootstocks-high-performing-disease-tolerant.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.

Bounty avocado rootstock

Maluma Hass (and other varieties like Pinkerton, etc) on the Bounty avocado rootstock grow a smaller more open tree (less leaf area) compared to all other rootstocks in the breeders orchard eg Velvick, Dusa, Martin Grande.
Don’t plant Bounty rootstock in good quality soil as it’s too vigorous.
Bounty rootstock appears to perform best in poor quality soils, waterlogged soils, heavy soils and generally in the poorest quality soil types.
Some of the orchard blocks had been in standing water for the past 3 weeks with little evidence of any effect on the variety planted on Bounty rootstock. According to the breeder, the Bounty rootstock can survive waterlogged soils for many days while any other avocado rootstock will die within 48 hours.
Phytophthora tolerance of Bounty appears to be similar to Duke 7 rootstock.
Maluma Hass propagated on Bounty in poor quality soils had an equivalent yield compared to Dusa and other rootstocks like Velvick in many of his orchard blocks. Tree size is smaller than all other rootstocks and the trees appear much calmer.
In summary, the Bounty avocado rootstock is recommended for planting in any marginal soils types including waterlogged or wet, heavy soils or in marginal climates affecting avocado production. Yield levels under these conditions would be similar to avocado trees grown in good soils on other rootstocks.”

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