There are three types of avocados: West Indian, Guatemalan and Mexican, according to horticulturists at Texas A&M University. California avocados are generally of the Mexican variety and grow quite well in Houston. Researchers at Texas A&M University suggest the Lula variety for Houston growers as it is tolerant of the high salinity levels in South Texas soils.
Remove all weeds from within a 4-foot radius of the California avocado tree. Weeds compete with the tree's roots for water and soil nutrients. Asiatic hawksbeard is a particularly hardy and invasive weed in Houston gardens, and hand-pulling of the weed is required.
Lay down 1/3 cubic yard of redwood bark or other organic mulch around the base of the tree, keeping it at least 6 inches from the trunk. Mulch will help to conserve soil moisture during the hot Houston summer and discourage weed growth.
Water the avocado tree with a drip irrigation system or soaker hose. The tree needs to be watered slowly, with at least 3 inches of water. Wait for the soil to dry prior to watering again. Depending upon the weather in Houston, the amount of time between waterings may vary. Slow, deep watering is important for avocados being grown in Houston to avoid leaf scald.
Fertilize your California avocado tree once a month from February to September. Apply 1/2 cup of a 21-0-0 formula fertilizer at each feeding during the tree's first year in the Houston garden. Increase the amount of fertilizer to 1 cup each month (February to September) in its second year and then 2 cups per month (February to September) during each subsequent year.
Protect the avocado tree in December and January, during the blue northers, by compacting soil 18 inches up the trunk of the tree. Although winters in Houston are generally mild, there is the occasional frost. Water the tree three days before and then cover it with a plastic tarp or a blanket if frost is in the forecast.