Pecan trees (Carya illinoensis) are native to the Mississippi flood plain of North America and are related to the English walnut, black walnut and hickory. The pecan tree is the state tree of Texas, lives for a long time (sometimes 200 years or more), is relatively resistant to diseases and is the largest of all the trees in the hickory family.
Pecan trees grow as tall as 70-100 feet and the trunk reaches a diameter of 6 feet. Under ideal conditions, the tree can reach a height of 180 feet. The leaves are made up of small leaflets that grow on opposite sides of the stems. The tree produces both male and female flowers. The male flowers are catkins--small, soft flowers that hang down from the stems--and the female flowers are star-shaped. Both types grow on the current year's twigs.
The nuts grow in clusters of two to six. They start out as a liquid and are enclosed in a husk. The tree will not start to produce nuts until it is 10-12 years old, and it will continue producing fruit for 4-12 years.
Pecan trees need long, hot summers--average temperatures from 80 to 115 degrees F--and cool, not cold, winters (average temperatures from 30 to 50 degrees F). They can survive with short periods with temperatures of 0 to -20 degrees F. The trees are hardy in zones 5-9--all but the coldest and the hottest zones in the continental United States.
The tree needs deep, fertile, well-drained loamy soils and full sun--at least 6 hours of sunshine a day. While the tree can grow in other soils, you will not get the same nut production. It also needs 1 to 2 inches of rain each week of the growing season. The trees do not do well with long periods of flooding.
Besides being used to produce a crop, either commercially or in a private garden, pecan trees make good shade trees as long as they are not planted near a sidewalk where pecans falling off can pose a hazard. They go better in the rear of the house, unless the front lawn is very large . The wood is used to make tool handles, flooring, veneer and furniture.
Pecan trees have problems with aphids and should be sprayed with an insecticide. Other insects that can damage the tree are the pecan nut casebearer, hickory shuckworm, nut curculio, pecan weevil and the pecan phylloxera. They also suffer from a zinc deficiency and should be sprayed with zinc sulfate, and need a fertilizer that is rich in nitrogen. The only disease that poses a serious problem is the pecan scab fungus.