There are three landraces of avocados. The Guatemalan types have the highest oil content and thick, pebbly skin. Their fruit may sit on the tree for up to a year and a half before maturation. The Mexican types are the most cold tolerant. They have thin skin, fragrant leaves, and are ready to pick in six to nine months. The third race is West Indian. These are too frost sensitive for California, and have low oil content. Most of the avocados we grow here are Guatemalan-Mexican hybrids, like the Hass. They combine the richness of the Guatemalan avocados with the frost tolerance of the Mexican avocados.
All avocado tree varieties are divided into type A and type B flowering cycles. Flowers of type A cultivars open in the morning as receptive females, then close until the following afternoon when they re-open as males, and shed pollen. Flowers of type B cultivars open in the afternoon as receptive females, close and reopen the following morning as males to shed pollen.
Therefore, male and female flowers are often not flowering at the same time which can make it hard to achieve pollination. For this reason, it’s recommended to plant an A and B type together. Although some avocado trees are able to self-pollinate.
How to Plant
- Before you plant, ensure your cultivar is right for you and your site and for you – they vary significantly including tree height, hardiness, fruit flavor, ripening and harvest time, and more.
- Planting early in spring allows young trees to harden off and begin establishing before the heat of summer and winter chill. This is why Epicenter starts selling their one-year-old trees right after the first frost date.
- Baker says that new trees should be planted on mounds 18 inches to two feet high, and six feet across, even when you have fast draining soil. She uses lots of aged manure and organic fertilizer in the planting hole, and the more mulch the better: With their shallow roots, avocados thrive in deep mulch. Never rake up the leaves – leave the leaves where they fall.
- Avocados do not do well in containers – they should be planted in the ground.
- Katherine Pyle, founder of the CRFG’s Golden Gate Chapter says, “To keep your avocado under eight feet, prune annually and don’t let it get out of hand.”
Heat and Frost Protection
- Weather over 95 degrees may deter fruit set. Keep trees especially well-watered when it’s hot.
- If the temperature drops below 25 degrees, Menge recommends putting coffee hulls (available for free from coffee roasters), straw, leaves or another kind of mulch to cover the trunk six inches above the bud graft and/or cover with nursery cloth. Baker recommends putting a few Christmas lights on the tree.
- If your tree suffers frost damage, the top of the tree may look dead. Gragg says, “That dead material protects the lower branches from freezing. In spring, the dead stuff falls off and the new growth comes out.” Says Baker, “As long as the trunk isn’t black, the tree will sprout back. It’s just cosmetic.”
- Bees are the prime pollinators of avocados. Gragg recommends boosting their numbers in and around the trees during their flowering period to increase fruit set. “Try bee-loving plants such as rosemary, or establish a hive near your trees,” says Gragg. Other attractive plants to try are borage, comfrey, native buckwheats, California fuschia, sages such as white, Cleveland or Sonoma, and sunflowers. You might also establish a bat house – bats also pollinate avocados.
- Planting both an A type such as Hass or Reed, and a B type cultivar such as Bacon or Fuerte, may dramatically increase fruit set. Gragg says, “Do this even if you have to plant both trees in the same hole because of lack of space.” Or do a planting project with your neighbor, like Stephanie Pascal and Meg Ronayne in North Oakland!
- If you grow a more tender variety outside your recommended zone, protect the trees when they are young and find a favorable microclimate on your site.
- Plant on slopes. Says Gragg, “This allows for excellent drainage to prevent root rot and increase frost protection because cold air sinks and accumulates on valley floors, bypassing the trees. If the slope faces south, the trees will enjoy more winter sun and warmth.” Areas above the fog belt can be banana belts.
- Avocados can do beautifully in the flats, especially in low frost areas with good sun and mild summers, like San Leandro and Alameda. Some areas of Berkeley and Oakland are also great fruiting areas. Katherine Pyle grows a vigorous and productive Gwen in her backyard. She says, “Gwen is not recommended this far north because of cold tenderness, but that tree is over 20 years old, bears most years, and has only been seriously damaged by cold once.“
- Given the right care and conditions, Mexican cultivars like Mexicola can grow and bear inland, such as in Concord and Livermore.
- The best place to store fruit is on the tree. Some varieties hold their fruit well for up to six months, while others don’t. Picking fruit only when needed may extend the harvest period for many months. The longer avocados sit on the tree the higher the oil content.
- Avocados are mature before picking, but not ready to eat. They must be softened off the tree. The softening process takes from a few days to a week or even longer. To keep them from ripening, refrigerate them. To speed up ripening, put them in a paper bag with an apple or a banana.
- Given the space, you can harvest all year round by planting varieties that ripen successively, since different avocado varieties flower and set fruit at different times.
- Once avocados get really big, they are unruly. To harvest, you must climb up to the tree’s extremities with your fruit picker, or rent a manlift. For easy harvest, keep trees below 12 feet.