Avocados (Persea americana) will grow in U.S. Department of Agriculture plant hardiness 8 through 11. They are grouped into three types or groups called "families" named for the areas where they were first cultivated domestically. These families include the Mexican, the Guatemalan and the West Indian. Their growth and yielding patterns vary.
If you buy a variety grafted onto a rootstock from a nursery, you will likely get your first avocados from three to five years after you plant it. If you plant a seed, it will likely take five to 13 years. It's natural for the first flowers to drop from the tree without setting avocados.
When a tree is ready to yield it will grow spikes of 200 to 300 yellow-green flowers that appear between late winter and early spring. When an avocado tree yields avocados depends on the variety and climate.
It's not always easy to determine when an avocado is ripe. If you pick them when they're still firm, they'll will ripen off the tree, but if you pick them too early, their skin will shrivel and they won't ripen. For signs they're ready to be picked, look for softening, loss of skin glossiness or a slight change of skin color from light green or purple to a darker shade of green or purple, depending on the cultivar. Another way to see if the avocados on your tree are ready for harvest is to pick a large one and put it on your kitchen counter. If it's mature, it should ripen in three to eight days.
Mexican and Guatemalan Avocados
Mexican avocados have smooth, thin skin. They are the most cold hardy and generally blossom in winter. They yield avocados from six to eight months later, in spring and summer 'Fuerte' (Persea americana 'Fuerte'), a Mexican variety, once the standard avocado in California's dry climate, will grow in U.S. Department of Agriculture plant hardiness zone 9b through 11.
Guatemalan avocados, intermediate in cold hardiness, have thick, often rough skin, and blossom in the spring. They yield avocados from 12 to 18 month later, in the following spring and summer 'Haas' (Persea americana 'Haas'), hardy in USDA zones 10 through 11, is the most popular avocado in the United States.
West Indian Avocados
West Indian avocados are large with thin skin and do not tolerate cold well. They like the more humid climates of Florida and the Gulf Coast. They blossom in spring and typically ripen in the summer of the same year. West Indian avocados are rarely grown in California's dry climate. 'Waldin' (Persea americana 'Waldin'), a large green avocado hardy in USDA zones 10b through 11, ripens in August through November in Florida.
Growing Avocados Indoors
You can grow an avocado from a seed indoors for its decorative foliage, but it's unlikely to yield avocados. To harvest avocados indoors, you need a dwarf variety allowed to grow to maturity. Dwarfs are too large for most household indoor locations. They yield avocados in greenhouses that can handle their size.
'Gwen' (Persea americana 'Gwen'), a Guatemalan dwarf hybrid hardy in USDA zones 10 and 11, yields avocados similar to 'Haas'; it will grow up to 14 feet high and yield fruit indoors. Outdoors its avocados ripen from February through October.