This species generally occurs in the ecotones or edges between longleaf pine uplands and pond pine pocosins (areas of dense shrub and vine growth usually on a wet, peaty, poorly drained soil) on moist to seasonally saturated sands and on shallow organic soils overlaying sand. Rough-leaf loosestrife has also been found on deep peat in the low shrub community of large Carolina bays (shallow, elliptical, poorly drained depressions of unknown origin). The grass-shrub ecotone, where rough-leaf loosestrife is found, is fire-maintained, as are the adjacent plant communities (longleaf pine - scrub oak, savanna, flatwoods, and pocosin). Suppression of naturally-occurring fire in these ecotones results in shrubs increasing in density and height and expanding to eliminate the open edges required by this plant. Several populations are known from roadsides and power line rights of way where regular maintenance mimics fire and maintains vegetation so that herbaceous species are open to sunlight.

 Rough-leaf loosestrife is a perennial herb that grows 11.8 – 23.6 inches (in) (30 - 60 centimeters; cm) tall. The triangular shaped leaves are often opposite on shorter stems (less than 30 cm tall) and tend to be arranged in whorls of three or four encircling taller stems. The leaves are widest at the base (0.3 – 0.8 in or 0.8 - 2.0 cm wide) and have three prominent veins. Contrary to the common name, the leaf surfaces are smooth to the touch. The yellow flowers are 0.6 (1.5 cm) across with yellow-orange anthers and occur on terminal racemes that are 1.2 – 3.9 in (3 - 10 cm) long. Flowering occurs from mid-May through June, with fruits (capsules) present from July through October. Since only a few stems in each population flower in any given year, surveyors shoud look for the leaves rather than yellow flowers. Stipitate glands are usually present on most parts of the plant. This species is easily distinguished from Loomis’ yellow loosestrife (Lysimachia loomisii) a similar southeastern species by its broader, glandular leaves and much larger flowers.

Rough-leaf loosestrife is easily distinguished from Loomis’ yellow loosestrife (Lysimachia loomisii) a similar southeastern species by its broader, glandular leaves and much larger flowers.