Longleaf Pine take a long time to mature. The can spend up to seven years in the "grass" stage, where looks like a clump of grass. Timber companies harvest the trees and replace them with faster growing species. Nature Conservancy is trying to restore some of the original stands in one of their preserves in this area. Here is some information on the life cycle of Longleaf Pines. http://www.longleafalliance.or...
Horntoad is correct. Longleaf pine take quite a while to get out of the grass stage. I have 3 in my yard that I have grown from grass stage. They are really interesting trees.