Fl. Bor.-Amer. 2: 226. 1803.
Trees, 5–10 m. Stems: branches ± brittle at base, gray-brown to redbrown, glabrous, villous, or tomentose; branchlets yellowbrown to redbrown, glabrous, sparsely or densely villous or tomentose. Leaves: stipules rudimentary or foliaceous on early ones, foliaceous on late ones, apex convex to acute; petiole (with spherical glands distally), (3–) 4.5–14 (–22) mm, tomentose or pilose adaxially; largest medial blade lorate or lanceolate to narrowly lanceolate, (50–) 75–115 (–220) × 10–22 (–35) mm, 5–10 times as long as wide, base usually convex or cuneate, sometimes rounded to cordate, margins serrate or serrulate, apex acuminate, acute, or caudate, abaxial surface glabrous or sparsely tomentose on midribs, hairs white and/or ferruginous, wavy, adaxial highly glossy, glabrous or pilose, hairs white and/or ferruginous; proximal blade margins entire or serrulate; juvenile blade glabrous, or moderately densely tomentose or silky abaxially, hairs white and ferruginous. Catkins: staminate 28–97 × 5–11 mm, flowering branchlet 4–25 mm; pistillate 33–93 × 7–15 mm, flowering branchlet 3–35 mm; floral bract 1–3 mm, apex acute or rounded, entire or erose, abaxially sparsely hairy, hairs wavy; pistillate bract deciduous after flowering. Staminate flowers: abaxial nectary 0.3–0.5 mm, adaxial nectary oblong to narrowly oblong, 0.3–0.6 mm, nectaries distinct; stamens 4–7; filaments (sometimes connate less than 1/2 their lengths), hairy basally; anthers 0.4–0.6 mm. Pistillate flowers: adaxial nectary oblong, square, or ovate, 0.3–0.7 mm; stipe 1.3–5.3 mm; ovary pyriform to obclavate, beak slightly bulged below styles; ovules 12–16 per ovary; styles (sometimes distinct distally), 0.1–0.2 mm; stigmas 0.16–0.2–0.28 mm. Capsules 4–6 mm.
Phenology: Flowering (south) Dec-early May, (north) mid Apr-early Jun.
Habitat: Alluvial woods on floodplains, swamps, hummocks, marshes, wet interdunal depressions, rocky or gravelly streambeds, ditches, canals, usually on calcareous substrates
Elevation: 0-600 m
Ala., Ark., D.C., Fla., Ga., Ill., Ind., Kans., Ky., La., Md., Miss., Mo., N.C., Ohio, Okla., Pa., S.C., Tenn., Tex., Va., W.Va., Mexico (Nuevo León), West Indies (Cuba), Central America (Guatemala)
Salix caroliniana forms natural hybrids with S. nigra. Hybrids with S. amygdaloides have been reported (N. M. Glatfelter 1898); no convincing specimens have been seen.
Salix caroliniana × S. nigra: This hybrid is characterized by stipes to 1.3 mm and leaves glaucous; it probably occurs wherever the two parents come into contact. In the southeastern United States, it occurs from northern Florida to West Virginia and Maryland with intergradation mainly on the Atlantic coastal plain from northern Florida and southern Georgia (G. W. Argus 1986). Reports (N. M. Glatfelter 1898) of it from the vicinity of St. Louis, Missouri, are unconfirmed.
"-0.28mm" is not declared as a valid unit of measurement for this property.