Epilobium angustifolium is a(n) perennial herb, which grows 0.5 m to 2 m in height. This species is commonly found in moist open forsts, thickets, and clearings, often following fires. It is also occasionally found at mid to high elevations in the central and northern Balck Hills and the Bear Lodge Mts. The leaves are spirally arranged, sessile or nearly so, lanceolate to narrowly lanceolate with a prominent midrib. Epilobium angustifolium has deep pink to pinkish-purple, rarely white, flowers that bloom from June to August.