Pecans
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The Pecan is the state tree of Texas. They will grow in every county. This link was written by some of the best students of Fred Bryson. Fred was one of the original experts of the Texas pecan industry.
For those willing to try here is the a link to the four flap graph method XXX that you can use on that volunteer tree that seem to appear out of nowhere in older landscapes.
For trees consider Womack Nursery. They have been the primary supplier to commercial groves for over 80 years.