Longleaf Pine – Living with Fire

There are three common species of large pines that live within the so-called pine belt of the southeastern U.S. This swath of land stretches from the coast of North Carolina, Georgia and Florida, westward to eastern Texas. Of these, Longleaf historically dominated this landscape. It evolved to not only tolerate fire but depend on it. In many ways, it is also one of the most elegant.

Longleaf Pine (Pinus palustris) can be the easiest to identify compared to its close relatives Slash Pine (Pinus elliottii) and Loblolly Pine (Pinus taeda). As the name implies, Longleaf has the longest needles, reaching upwards of 12 inches. It also has the largest cones. But the most striking of its characteristics is its habit (shape), especially how needles are arranged on its branches.

Needles in pines are held together in bundles called fascicles. In Longleaf, there are three needles per bundle that are situated at the tip of robust branches, forming a ball. If you view the tree as a whole, this arrangement resembles a candelabra, with the balls of leaves held upward from the tip of each branch. Liberace would be proud.

Loblolly Pine needles are also in bundles of three, but much shorter (5-7 inches). Slash Pine needles are intermediate in length (7-10 inches) but usually with only 2 needles per bundle, but sometimes three – the sneaky devil. But unlike Longleaf, needles on these trees are more scattered along the branches, in some cases looking more like a fan at the tip of branches.

When it comes to the size of cones, Longleaf also takes the prize, with the largest (8-10 inches). Cones of Slash Pine are shorter (6-8 inches) with Loblolly Pine having the smallest (4-6 inches). The cones of Loblolly also persist in the tree for years, making it easier to spot.

But one of these characteristics of Longleaf Pine explains its ability to survive fire, especially in its early years. Fire is a naturally occurring factor in the southeastern pine belt, historically occurring every 3-5 years. Pines dominate here because they have fire-resistant bark and needles, both of which only burn under persistent flames. Flames of natural fires last only a minute or two at any one spot, allowing bark and some needles to survive.

Longleaf takes this strategy a step further, especially for small saplings that hug the ground in the early years. These small trees are called grass-stage pines, for their resemblance to tuffs of grass – in this case a ball of long needles that protect the central growing tip of the tree. This is when having long needles pays off. These long, fire-resistant needles keep flames away long enough to keep fire away from the growing tip.

The grass stage lasts a few years, during which the plant builds a deep tap root and robust trunk, covered with fire-resistant bark. Once the small tree does begin to grow taller, the larger diameter trunk also protects it from fire. This is not the case for Slash or Loblolly pines that shoot up quickly with small diameter trunks that are susceptible to fires in the first years of growth.

This adaptation to fire early in life explains the historical dominance of Longleaf Pine in upland forest and wet pine savannas across the pine belt. In pre-European forests, the only tree in these habitats were Longleaf, with biologically diverse grasslands beneath the canopy, also having adaptations to fire. Humans have altered that cycle.

But the queen of pines remains, if not in its former glory, certainly around enough to give our pine forest an elegant look.

Hope to see you in our great outdoors!