The longleaf pine tree is a survivor. It grows well on nutrient-poor and sandy soils and requires very little maintenance once established---it is even partially fire resistant. Part of its hardiness is due to its slow but steady growth. The longleaf pine can grow to 80 feet. But you are unlikely to see your longleaf pine tree reach its height potential in your lifetime. It takes 100 to 150 years for a longleaf pine tree to reach its maximum height.
Remove all vegetation in at least a 5-foot circle centered around the planting site. Dig up weeds and grass directly or first spray them with a broad-spectrum herbicide before digging. Any trees or large bushes should be dug by hand.
Water the soil with 2 to 3 inches after all the vegetation has been killed and removed.
Dig up the planting area (at least 2 feet deep in circle with 5-foot diameter centered around the planting site) with a shovel to loosen the soil. Break up any large clumps of soil and remove any rocks or plant debris that you encounter along the way. Stop when the soil has a fairly even, loose texture. Walk over the soil when you're done to remove any air pockets and smooth the soil.
Dig a hole that is three times the diameter but just as deep as the container that your longleaf pine tree seedling is currently in. Fill the hole with water and allow it to drain.
Remove the seedling from its container. Take care not to disturb any of its root, especially the long taproot at the center of the root ball. Loosen the tree's roots by gently pulling them away from the root ball with your hands.
Plant the tree in the hole so that its taproot is pointing straight down and its root collar (the point where the roots meet the trunk) is less than 1 inch above the ground line. Pat the soil down with your hands to firm it when you are done.
Water the pine tree with a slow-running hose placed near its base until the soil is moist below the tree's root ball. Insert a wooden dowel into the soil to help you ascertain the moisture depth. Continue to keep the soil moist to this depth with regular watering and frequent moisture-level checks.
Spread a 3-inch layer of pine-needle mulch around the cleared planting area to help keep the soil moist and the weeds at bay.