How to grow Avocado

Where to plant

Avocados need warmth, full sun and, above all, good drainage. They do not tolerate flooding or soil that stays wet, which brings Phytophthora root rot and kills trees. UC also advises avoiding sites with hardpan or rock within 3 feet (1 m) of the surface, or lime deposits. Give the tree plenty of room, as shade from buildings and other trees cuts the crop.

In Florida, the warmest areas along the southeast and southwest coasts suit every type. In Central Florida, choose the hardier hybrids, and in North Florida, the Gulf South and Texas, only cold hardy Mexican types such as Joey or Lila, planted in the warmest spot and covered on freeze nights. In California, avocados grow along the coast and in frost free inland valleys of Southern California, and in the warmest sheltered parts of Northern California. The low desert is too hot and dry, and the rest of the country is too cold except in a greenhouse.

Choosing a variety

Avocados come in three races. West Indian types have large, mild, lower oil fruit and are the least cold tolerant, suited to South Florida and Hawaii. Guatemalan types and their hybrids are a little hardier. Mexican types have small, thin skinned, rich fruit and the most cold tolerance. California's Hass is mostly Guatemalan; Florida grows mostly West Indian and West Indian by Guatemalan hybrids, which mature from June to March depending on variety, so a few varieties can spread the season.

Avocado flowers open as female and male at different times of day, and varieties are either A type or B type depending on that timing. A single tree usually sets some fruit, but UF/IFAS suggests planting one of each type for better pollination.

How to plant

1. Plant a grafted container tree in spring, after the last frost, so it settles in before summer heat and has a full season before winter.
2. Dig a hole about twice the width of the root ball and only as deep. Do not add compost, topsoil or fertilizer to the hole.
3. Set the tree so the top of the root ball sits level with the soil or about an inch above it. Planting too deep lets water stand against the trunk and invites root and crown rot.
4. Backfill with the native soil, make a shallow watering basin about a foot from the trunk, and water well.
5. Paint an exposed trunk with white interior latex paint diluted half and half with water to prevent sunburn.
6. Mulch over the root zone, keeping the mulch a few inches from the trunk.

Watering and feeding

UF/IFAS advises watering a new tree at planting, every other day for the first week or so, then once or twice a week for the first couple of months. Through the first three years, water young trees twice a week during dry spells of five days or more. Older trees benefit from watering in long dry spells, especially from bloom through fruit growth. In California's dry summers, UC suggests about 2 inches of water a week for a mature tree, split into several waterings depending on soil. Underwatering gives small, sunburned fruit, and overwatering brings root rot.

Mature trees need regular nitrogen; UC suggests applying it in fall or winter in California. In Florida, young trees are fed lightly and often. Trees in containers or dwarf trees need less.

Pruning and care through the year

• Pinch the tips of young upright trees from the second season to make them branch, so the fruit forms lower down and the tree stays manageable.
• Prune sparingly and avoid late season pruning, which pushes tender growth that frost can damage. Paint newly exposed branches white to prevent sunburn.
• Cover young trees on freeze nights. Cold damage depends on the variety, how long the cold lasts and the tree's exposure.
• In Florida, never bring in firewood or wood from laurel family trees, which can carry the beetles that spread laurel wilt.

Harvesting

Avocados do not soften on the tree; they ripen after picking, once mature. In Florida, maturity is set by calendar date and fruit size for each variety. In California, maturity depends on oil content. The simple home test is to pick one full sized fruit and leave it indoors: if it softens evenly in about a week without shriveling, the rest are ready. Green skinned varieties often turn yellowish green, and dark types turn from green to black.

Clip fruit with a short piece of stem rather than pulling it off, which hastens decay. Many varieties hold on the tree for weeks after maturing, so pick as needed. Mature trees in Florida average 2 to 3 bushels a year.

Growing in pots

Avocados grow into large trees, so a pot is a short term option. A compact or dwarf variety in a pot at least 24 inches (60 cm) wide can be kept on a sunny patio and moved under cover in cold areas, but expect few fruit. Use a fast draining mix and never let the pot sit in water.