Although sprouting the seed of a store-bought avocado (Persea spp.) is simple, the plant may not bear fruit for up to 15 years. Avocado trees are propagated through grafting, which means the stem of one avocado variety is spliced onto another avocado variety. The technique yields quicker harvests, consistent fruit quality and disease-resistant avocado trees. Pollination, climate, soil, water and diseases are among variables that affect growing a healthy, fruitful avocado tree.
If you want to grow an avocado tree as a specimen plant without regard to fruit production, then you may plant a single avocado tree. If, however, you want to harvest your own avocado fruits, then more than one avocado tree must be planted. An avocado tree needs to cross-pollinate with another variety of avocado tree for optimal fruit set. Although avocado flowers have both male and female flower parts, each part functions at a different time during the day. Avocado trees are grouped into Type A and Type B, depending on the time of day their male and female flower parts are reproductively viable. Planting a Type A tree and a Type B tree increases successful pollination if enough insect pollinators, such as bees, are present.
The condition most limiting to growing an avocado tree is cold weather, according to the Texas A&M; System AgriLife Extension website. All three primary avocado species are tropical plants: West Indian (P. americana Mill. var. americana), Guatemalan (P. nubigena var. guatamalensis L. Wms.) and Mexican (P. americana var. drymifolia Blake). Mexican varieties are the most cold-hardy, but they can tolerate cold temperatures to only about 20 degrees Fahrenheit. In a residential setting, the south or southeast side of a house is the warmest location, and so it is the best place for an avocado tree. During freezing weather, it helps to drape blankets or tarps over a young tree and anchor the coverings to the ground. If an avocado tree is large, then mounding soil or mulch high on the tree trunk for winter can help the tree survive cold temperatures.
Soil, Water and Fertilizer
An avocado tree can grow successfully in a variety of soil types and in soil with acidic or alkaline pH levels, but the tree requires soil that has good drainage. It declines in poorly draining and saline soil. Because West Indian varieties are more salt-tolerant than Mexican varieties, they are better choices in coastal regions. An option is to plant a Mexican variety that is grafted onto a West Indian rootstock. Although an avocado tree cannot tolerate wet soil, it needs at least 1 inch of water every week during periods of insufficient rainfall. Not fertilizing the tree until it is 1 year old is recommended on the California Rare Fruit Growers Inc. website. Young trees need four applications of a balanced fertilizer, such as 10-10-10, and older trees need twice-yearly applications of a high-nitrogen product applied in early summer and late winter.
Avocado root rot is the most serious disease of avocado trees, according to University of California Integrated Pest Management Online. This disease, which is caused by the pathogen Phytophthora cinnamomi, thrives in poor drainage conditions. Pale leaves, wilted leaves, branch die-back and small fruits are consequences. Applying a layer of gypsum and a 4- to 6-inch layer of an organic, coarse mulch underneath the avocado tree's canopy but several inches from the tree's trunk supplies calcium and suppresses the development of root rot. Anthracnose, caused by the pathogen Colletotrichum gloeosporioides, infects an avocado tree's fruit, flowers, small branches and foliage, leaving spots, lesions and decay. This disease thrives in areas of high humidity, dense fog and mild winters. Pruning limbs to at least 2 feet off the ground increases air circulation at the base of the tree and raking debris from underneath the tree prevent overwintering pathogens.
- Texas A&M System AgriLife Extension: Avocados
- University of Florida IFAS Extension: Avocado Growing in the Florida Home Landscape
- California Rare Fruit Growers Inc.: Avocado
- University of California Integrated Pest Management Online: Management Guidelines for Avocado Root Rot (Phytophthora Root Rot)
- University of California Integrated Pest Management Online: Management Guidelines for Anthracnose on Avocado
- University of Florida IFAS Extension: Florida Crop/Pest Management Profile -- Avocado
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