Growing Avocados
By Bob Chapman
Whether smooth green skinned or black and warty, the avocado is a taste treat. Its many uses in the kitchen and on the table make it a very popular addition to the diet. But, they are a challenge to grow. Avocados with their large, dark green leaves are excellent shade trees, but few plants will grow under them because of the density of the shade.
Avocado oddities
Growers of avocados are often perplexed about the "funny" events that happen when growing avocados.
-Leaf drop can occur at almost any time of the year. It precedes the new foliage, which appears a coppery-red when opening.
-Cool weather during fruit set can severely limit fruit set. High temperatures after fruit set can cause the fruit to drop.
-Usually the heavy shade of the avocado tree will not allow much to be grown under it. If you decide to try a lawn, use fescue, either seed or sod, but keep the lawn three feet from the trunk.
-Green varieties of avocados take about 10 months to ripen from fruit set or pollination. Black ones take 13-14 months.
-You can't tell the variety by the time of pollination, only by the fruit itself. The "Fuerte" has smooth-skinned, green avocados. The "Hass" is rough-skinned and black.
-Avocado tree trunks can get sunburned when young. Paint the trunk with white latex paint. It is not needed when the canopy gets wide enough to provide shade to the trunk all day.
Pollination
-Pollination of avocados is strange. Most are self-fruitful, but most will bear more and better fruit if pollinated with another variety. Avocado flowers are classed as type A or B. Varieties with type A flowers are receptive to pollen in the morning, but don't release their pollen until the afternoon of the following day. The situation is reversed in type B avocados: the flowers are receptive in the afternoon but don't release pollen until the next morning.
-Combining varieties with different flower types produces higher yields. Commercial growers will graft branches on their trees to increase yields. Most trees produce enough fruit for an average family without the necessity of grafting other types.
Avocados: when they ripen, type of flower
-Hass: Black skin, ripens spring to fall, type A flower
-Fuerte: Green skin, ripens fall to spring, type B flower
-Bacon: Green skin, ripens fall to winter, type B flower
-Zutano: Green skin, ripens fall to mid-winter, type B flower
Grafting
If grafting is desired, T-budding is the preferred method. Grafting avocados is done in the spring and summer when the trees are actively growing. Select fat buds from the ends of the branch and graft these onto the desired tree on the newer growths. See Sunset's "Western Garden Book" for illustrated instructions on how to do this simple procedure.
Soils
Avocados prefer an acid soil (a pH of 7.0 or below) and you may have an alkaline soil. Applying soil sulfur, if needed, and using sulfate of ammonia, should keep the soil pH low enough. Purchase a Sudbury Garden Soil Tester. This is designed to test pH only. It costs about $4 and gives ten tests and gives suggestions for improving the pH of the soil by the addition of aluminum sulfate. Meters that register the moisture content, the pH and the light levels are a great addition to your list of tools. You'll find sulfur, sulfate of ammonia, soil testing kits and moisture and pH meters in the inside garden department of our stores. Our sales associates will be glad to show them to you.
Fertilizing avocados
Fertilize your avocado tree in March, June and August. Give it three applications of sulfate of ammonia, at the rate of ½ pound per inch of trunk diameter at each feeding. Spread it around under the canopy and water it in thoroughly after applying.
Watering your avocado
Feeder roots, sensitive to moisture excess or deprivation, are found in the upper 15 inches of the soil. Water avocado trees when the soil is dry three inches below the surface. Apply enough water to soak the soil 18 inches deep. Water it only when the soil dries, as stated above.
Pruning
Avocados can be cut down to stumps and survive. This is sometimes done to resurrect older trees that have become too big and widespread. So prune to your hearts content at any time of the year except during flowering (the branches are weakened when cut at this time). You won't harm the tree. Be aware, however, that branches severely cut back may not produce flowers for three years. It will take that long to produce fruiting wood.
Root rots
Lack of soil drainage can cause problems especially in clay-based soils. Root rots (identified by a gradual decline in size of the foliage, dying branches, no new growth and a dark streak under the bark when stripped away) are caused mainly by planting, or trying to plant, lawn around the base.
Harvesting
-When you think the fruit is ripening, (the dark skinned avocados will start turning from green to black when reaching maturity, the green ones will develop a yellowish tinge), pick one of the larger ones. Place it a brown paper bag with a ripe banana or an apple for a couple days. When ripe, it will feel soft. Remove the flesh and check the seed coat. The thin membrane surrounding the seed should be dark brown if the fruit is ripe and ready for picking. Immature fruit will have a light tan or yellowish seed coat.
-When harvesting, use a hand-held pruning shears, leaving a small piece of stem attached. This helps prevent decay during ripening or storage.
-Mature fruit will stay on the tree, as a natural storage receptacle, for 8-20 weeks after ripening. If they stay on the tree longer they may get soft and lose flavor. Pick the avocados when they are hard, softening or ripening them off the tree.