Avocados have a creamy texture and buttery, slghtly nutty flavor that make them popular. In addition to tasting good, they are also a source of healthy fats, fiber, vitamins and minerals.
Avocados are native to southern Mexico, Central America and the West Indies. The fruit has long been used as a food by Native Americans in these regions and was known by the Aztecs as “ahuacatl.” They grow best when temperatures do not drop below 32 degrees F. Because of their temperature sensitivity, avocados are mostly grown in coastal California from San Diego to Monterey, frost free inland areas in San Diego and Riverside, and temperate areas of the San Joaquin Valley.
Varieties
Avocado varieties are defined as Guatemalan, Mexican, West Indian, or a hybrid. West Indian varieties do not tolerate cold well and are not typically grown in this area. Guatemalan varieties such as ‘Nabal’ and ‘Reed’ are sensitive to cold temperature/frost. Mexican varieties can tolerate cold, even below freezing temperatures in moderation. The Mexicola variety is the most frost tolerant and stays healthy even with temperatures in the low 20’s. One of the most popular varieties, Hass, is a Guatemalan/Mexican hybrid and is damaged if temperatures remain at 30 for four hours. Another popular Guatemalan/Mexican hybrid, Fuerte, can tolerate up to four hours at 27 degrees F.
Protective measures such as a blanket to trap warm air, a heat lamp, or water offer protection. Heat is also a concern. Temperatures exceeding 1000 F for long periods of time cause poor fruit set and excessive fruit drop. Temperatures that are too low can affect fruit set if spring daytime temperatures remain below 700 for extended periods of time. Providing shade, overhead sprinklers, evaporative cooling, and other cooling measures help reduce these problems and many home gardeners successfully grow this popular fruit.
For success, choose a variety that is the most frost tolerant, and take precautions to protect trees from extreme temperatures. Here are a few varieties and information about each of them:
| Variety | A or B | Frost Sensitivity |
| Haas | A | Tolerant to 30 F |
| Fuerte | B | Tolerant to 27 F |
| Stewart | A | Tolerant to 18 F |
| Mexicola | A | Tolerant 18 to 20 F |
Cultivation
Growing an avocado tree from a seed is a fun experiment for kids but be aware that it can take 5 to 10 or more years for those trees to bear fruit. Most commercially grown avocados consist of a disease resistant root stock. Growing a plant from seed may not yield a healthy tree. An easier way is to purchase ready to plant trees.
Avocados need well drained soil and grow well in sandy loam soils with good drainage, which is common in Stanislaus County, but they don’t do well in clay soils. Mulching with green waste compost is valuable but manures are too high in salts and ammonia and can lead to root and tip burn.
Avocados can grow to be quite tall, so plan to prune them regularly, or plant away from structures. When possible, avoid planting in lawn areas as their water needs are different and grasses will compete with avocados for water. Avocados are prone to dropping leaves so avoid areas near water features such as pools. Avocados prefer full sun.
Avocados do well in native soil and do not require expensive soil amendments. Roots are shallow, generally no deeper than 8-10 inches. Dig a hole twice the diameter of the container and the same depth as the plant. Place the tree in the middle of the hole and backfill with native soil. Tamp lightly but don’t pack too heavily.
Pollination
Each variety of avocado has a gender. Avocados are generally characterized as A – female and B –Type A avocado flowers open as female in the morning of the first day, then close and reopen as male in the afternoon of day 2. Type B avocado flowers open as female the afternoon of day 1, close and reopen as male the morning of day 2. This allows a single avocado tree to self-pollinate, with a bit of help from Mother Nature in the form of gravity, mild winds, or insects to transmit pollen among flowers. For better results plant two trees or make sure there is another avocado close by as avocados prefer cross pollination for good fruit set. If both flowering types are nearby and bees are available, maximum pollination occurs. A chart listing the avocado varieties and type (A or B) can be found here. https://ucanr.edu/sites/alternativefruits/files/151223.pdf
Irrigation
Avocados require a lot of water, with fully mature trees needing up to 50 gallons per day. Soil type, sunlight, temperature, humidity, and wind all affect the amount of irrigation needed. Drip irrigation is best as it can be moved as the tree grows. Initially place drippers close to the root ball. As the tree grows move the drippers to the drip line and add drippers if needed to thoroughly water the tree.
Our hot dry climate necessitates watering more frequently than the more moderate climate conditions of the coast or southern California. Check the soil regularly and water before the soil is completely dry. You may need to water more often if you have a sandy soil, and less for clay soils. To be sure, dig down in another area to 18” deep to see how deeply water penetrates and how quickly soil dries out.
Fertilization
To maintain a healthy tree and good fruit production, avocados require regular fertilization. Native soil provides most of the nutrients but is often lacking the amounts of nitrogen and zinc needed for optimal growth. Generally young trees will require a quarter pound of nitrogen while mature trees will require 1.5 to 2 pounds. A typical fertilization schedule for mature trees is to apply 6 pounds 15-15-15 in February, 3 pounds 15-0-0 in June, and 3 pounds 15-0-0 in September. Young trees will require ¾ pound 15-15-15 in February and ¼ pound 15-0-0 in June and September.
Pest Problems
Avocado root rot is caused by the fungus Phytophthora cinnamomi and is the most important disease of avocados. It is worse in poorly drained soils so plant trees in these conditions on mounds to improve drainage. Often, trees are buried too deeply, which results helps provide the disease with an entry point. See figure X for how to plant correctly.
Sunblotch is a viroid disease that causes sunken yellow blotches on fruit and stems. It cannot be treated and diseased trees should be removed. Several varieties of thrips and mites also attack avocados. More information on recognizing and treating pests can be found in the reference material.
Happy Planting!
Avocados are fruits, but because of their savory flavors they are often considered a vegetable. Growing an avocado tree(s) will reward you with your own source of fresh avocados to put in yummy foods such as salads, soups, guacamole, eggs, and pasta!
Resources on planting and caring for avocados:
https://ucanr.edu/sites/alternativefruits/files/151223.pdf
Growing Healthy Citrus and Avocados in the Backyard
https://ucanr.edu/sites/alternativefruits/files/151223.pdf
UC Riverside Avocado Variety Collection
https://avocado.ucr.edu/
Barbara Kissinger Santos has been a UC Master Gardener in Stanislaus County since 2024.