Unless you live in isolated pockets of east, central and south Texas, you will need to grow your olive tree as an ornamental, and here's why. Fruiting of the olive tree, which occurs in the winter, depends completely on temperature, more precisely what agriculturalists call vernalization. The olive tree must be exposed to cool night and warm daytime temperatures in order to set fruit. It will, however, sustain damage if the temperature drops to below 17 degrees F and die if it goes down to 10 degrees, F. These climactic requirements leave out all but a few sites in Texas as suitable for olive growing, according to botanists at Texas A&M University.
Water the olive tree enough to ensure that it doesn't dry out. The roots are shallow, so if the weather is particularly warm, you may need to water more often. Keep an eye on the soil and if it appears dry, and a finger poked one inch into the soil comes out dry, it's time to water.
Fertilize the olive tree in December. Agriculturalists at Texas A&M University suggest 1/2 to 2 pounds of nitrogen per year, for the mature tree. You will find nitrogen fertilizer in a gardening center sold as ammonium nitrate, or sodium nitrate.
Prune the olive tree in early spring. Thin out any dead or loose branches. If you are planting a young olive tree it should be trimmed to three or four scaffold branches. This is known as training the tree and to do this, begin by trimming away any weak branches. Choose 4 strong branches, equally spaced around the tree. The lowest two branches should be longer than the top two, giving the olive tree a Christmas-tree effect. Remove all other branches from the tree. Finally, go back to your four scaffolding branches and remove any shoots that are pointing up, and all those that are less that 12 inches in length.
Prepare the olive tree for winter in late November. Pile one and one half feet of soil around the base of the tree, and up the trunk. Remove the soil in March. If winter temperatures below 17 degrees F are expected, cover the tree with a blanket or tarp.