Physiognomy and Structure: These are open woodlands. The trees are primarily needle-leaved evergreen conifers and often are straight, well-formed, and moderately tall. Open canopies and grass-dominated understories are typical of sites managed with prescribed fire. Sites lacking a hardwood midstory were more prevalent prior to the twentieth century. Serenoa repens is a dwarf palm shrub which is common in southern examples of this vegetation. These forests occur in flat lower coastal plain landscapes.

Floristics: This vegetation is naturally dominated by Pinus palustris. Low shrubs, mostly ericaceous, may be abundant, such as Vaccinium spp. and Ilex spp. In addition, Serenoa repens is a characteristic species, particularly in South Carolina, Georgia, and Florida. East of the Mississippi River, Aristida stricta (in North and South Carolina) or Aristida beyrichiana (from South Carolina to Mississippi) is usually the dominant or at least a characteristic herb. In central South Carolina and west of the Mississippi River, both of the Aristida species are absent and various other grass species dominate (Andropogon spp., among others). Some of these mesic flatwoods associations have among the highest species richness values measured at the 1/10-ha scale. Forbs, especially composites, are usually also an important herb component, and lichens are abundant in some associations. Some typical mesic to dry-mesic herbaceous species include Andropogon ternarius, Andropogon gyrans var. gyrans, Schizachyrium scoparium, Sorghastrum nutans, and Panicum virgatum. Stands in south-central Florida may contain Panicum abscissum.

Dynamics:  Frequent fire is the predominant natural disturbance of this group. Sites naturally burned every few years, many averaging as often as every two years. Fires are naturally low to moderate in intensity. They burn above-ground parts of herbs and shrubs but have little effect on the fire-tolerant Pinus palustris trees. Vegetation recovers very quickly from fire, with live herbaceous biomass often restored in just a few weeks after growing season fire. Many plants have their flowering triggered by burning. In the absence of fire, species which are less able to withstand fire increase. Acer rubrum, Liquidambar styraciflua, Quercus nigra, Ilex spp., and other shrubs are reduced by fire, but without fire these broad-leaved woody plants can become tall and dense and can reduce Pinus palustris tree regeneration. Herb layer density and diversity decline in the absence of fire. On most soils, vegetation undergoes substantial structural alteration and reduction in species richness after just a few years without burning. Canopies are naturally many-aged, consisting of a fine mosaic of small even-aged patches of Pinus palustris driven by regeneration in canopy gaps. Longleaf pine is shade-intolerant and slow to reach reproductive age but is very long-lived. Some insect populations recolonize burned areas from nearby unburned patches. Sites managed with late spring or growing season prescribed fire provide high arthropod biomass (James et al. 2001, Taylor 2003).