This small "upland" or "prairie" willow is a widespread variable eastern species, reportedly including tetraploids (2n = 76) as well as diploids (Argus 1986, FNA 7). Plants are mostly (0.3) 1-2 (3) m talll. S. humilis (sensu stricto) is often confused with occidentalis, and some records need checking; see notes under that name. Also, early records of the more northern species, S. candida Fluegge (Defries 1884; Pr, Gm), may well have been based on misidentifications of humilis (M). In Ky. both humilis and occidentalis appear to have been formerly abundant in brushy transitions from woodland to native grassland, often in association with species like Corylus americana on drier sites or Spiraea tomentosa on damper sites. These willows were "a conspicuous feature in the Barrens" (Michaux 1793-96; Short & Peter 1835, p. 338 as "conifera" and "longirostris"). S. humilis has remained relatively common in rougher woodland edges, old fields and fencerows at some localities, but it is not particularly weedy. Vegetation with an abundance of this species (or perhaps occidentalis) was probably widespread across eastern states before settlement, but it has now largely disappeared. In the National Vegetation Classification (NS), it is reported only from sandy prairies of n. Ill. and n. Ind. (CEGLs 5069 & 5072), plus some Appalachian glades of Va. (CEGL 6239).