Years ago, I would plant seeds from avocados that I purchased at grocery stores. Avocado trees would easily sprout from the seeds and begin to grow. If I was lucky and winters were not too cold, I could get the tree to live through winters. No matter how hard I tried, or how old the tree became, it never flowered or fruited.
I learned very early that Hass and other varieties that are sold in groceries would not produce in Houston. And year in and year out, I hear stories of people growing from seed and wondering why the tree didn't produce.
The answer is simple. Most avocado varieties do not like freezes or frosts, and some require pollinators.
And then came the Mexican avocado varieties that are cold hardy and actually produce good tasting fruit. Bill Schneider of Devine Avocados near San Antonio starting raising Mexican avocados and produced a couple of really cold hardy varieties named Wilma and Opal. This was the start of a renaissance of growing avocado trees in metro Houston. Other varieties are also cold hardy such as Poncho and Fantastic.
The trees can grow quite large over time taking up 15' or more in diameter and 25' or more tall. They can be pruned to keep at a manageable height.
There is a little care needed the first year after purchasing one of these beauties. The trunk, which is green the first year outside of cold frame, has to be protected from the summer sun, and the tree has to be protected from winter freezes. After the first year of protection, they will thrive in all temperatures.
To protect from the summer sun the first year, the trunk can be wrapped in burlap or other cloth, or a tent of your own making can protect from the southern and western sun. To protect from freezes, place a 5-gallon bucket of water next to the trunk. When there is going to be a frost or freeze, wrap the tree in a blanket or two with the bucket inside of the blanket. This will keep the temperature around 32 degrees rather than lower.
My Opal avocado tree has produced for two years, but didn't this year, I think because of the exceedingly cold weather, but still looks great and has grown a lot. It is now about 10' tall and 7' wide and ready to put on lots of flowers during the winter and fruit in the spring.
I'm still experimenting on when to pick the fruit, for it matures on the tree, but needs to sit on a kitchen counter top for a few days to ripen.
The trees need to be purchased when they are available which is usually during the winter fruit tree sales, and then planted in the ground in early April. The tree can be planted in a slightly raised bed to insure good drainage. I built up a mound, planted the tree and then mulched heavily with leaves over the soil.
I fertilized the first year in May, and subsequent years in late February and May, with an organic granular fertilizer. I sprinkled about 4 cups under the canopy of the tree, and watered. You definitely need to keep this tree watered during the summer, but make sure the roots don't stay wet all the time.