Although the longleaf forest once dominated a large area, it is not a climax forest type. It is a sub-climax forest, kept at that successional level by fire. Natural or man-made fires may have historically occurred every two to four years. Since longleaf is fire tolerant, it survives fires that kill its woody competitors. This results in a monotypic over story, sparse mid story, and diverse herbaceous under story, making functioning longleaf forests one of the most biodiverse forests in the world.
Longleaf pine seed production is quite unpredictable and good seed crops may only occur every five to seven years and seed failures may happen once every five years, depending on the stand location. Bumper crops in East Texas usually occur only once every fifteen years. The year 2014 was a bumper year for longleaf in the Angelina and Sabine National Forests in East Texas. The longleaf had an average of 45-78 green cones per tree. Autumn seed production may be predicted by visual observation of green cones in the canopy in the spring of the year.