Avocado

Avocado trees are fascinating. Unlike most fruiting trees, which can be either self-pollinating or not, avocado trees are both and neither. Confused? Read on!

Avocado fruit and foliage (B.navez) CC BY-SA 3.0

Avocado flowers

Avocado trees flower with a behavior called synchronous dichogamy. Each flower is both male and female, but at different times. Also, there are two kinds of flowers: Type “A” and Type “B”. "A" avocados include Haas, Gwen, Lamb Haas, Pinkerton, Reed, GEM and Harvest varieties. Bacon, Ettinger, Fuerte, Sharwil, Sir Prize, Walter Hole, Zutano, Marvel and Nobel are "B" avocados.
​
When an "A" avocado flower first opens in the morning, it is female for a few hours and then it closes. The next day, the same flower reopens in the afternoon, but this time it is male. When a "B" avocado flower opens for the first time, in the afternoon, it is female. Then it reopens the next morning as a male. Since a mature tree produces over one million flowers in a season and the flowers open on different days, there is no need for another tree for pollination to occur.

How to grow an avocado tree

Many of us have used toothpicks on an avocado pit with dreams of a productive tree. You can make that dream a reality with these tips (and a lot of patience).

To start an avocado tree from seed, simply insert 3 or 4 toothpicks into the sides of the seed and suspend it, fat end down, over a glass of water. One inch of the seed should be submerged. In 6-8 weeks, the stem and roots will emerge. To improve structural growth, cut the stem back to 3 inches when it reaches a height of 6-7 inches. When leaves reappear, move the young tree to a 10-12” diameter pot filled with rich soil or to your yard. Be sure to leave the seed half exposed. Water frequently and give it plenty of sunlight.

Sprouting avocado pits (KVDP)

When the seedling reaches a height of one foot, cut it back to 6 inches. This will promote the growth of fruit producing branches. It will take 5-13 years to start producing fruit.

If you don’t want to wait that long, plant a bare root tree. The best time to plant is March and April. Young avocado trees don’t take up water very well, so summer months are too hot to start a young tree. When planting, dig a hole that is twice as wide as the root ball and only as deep as the roots. Avocados are shallow rooted, which means most of the roots are in the top 6 inches of soil. Most trees fail because they are planted at the improper depth.

Also, avocado roots are very sensitive to damage, so treat them gently as you fill the hole with nutrient rich soil. If the soil is heavy clay, elevate the tree a little bit, in a mound, to avoid drainage problems. The mound should be 1-2 feet high and 3-5 feet in diameter. Be sure that there is no lawn within several feet of the tree. Mulch will help retain moisture, just don’t let it touch the trunk to avoid borers or fungal disease. Avocado trees prefer a soil pH of 6-6.5 for optimal growth and they need a lot of nitrogen and zinc.

Avocado seedling (Mark Hofstetter) CC BY 2.5

Young trees need to be watered two or three times a week. Water heavily, but let the soil dry out between waterings. By the end of the first year, water once a week. A mature tree will use as much as 20 gallons of water a day during the peak of summer.

Avocado pests and diseases

Common avocado diseases include avocado root rot, bacterial canker, dothiorella canker, leaf blight, phytophthora root and crown rot, stem blight, sunblotch, and verticillium wilt. Avocado lace bugs, latania scale, mealybugs, mites, nematodes, omnivorous loopers, orange tortrix moths, soft scales, thrips, and whiteflies will all be attracted to your avocado tree. Birds and squirrels will join in the feeding fray, so you may want to build a tree cage around part of your avocado tree.

If you have the time and the space, growing an avocado tree in your yard can provide decades of the best guacamole ever!