9. Rubus argutus Link

Pl. 542 h, i; Map 2507

Canes to 450 cm long and 120–400 cm tall, 3–7 mm in diameter. Prickles sparse, 0.3–1.0 per cm of cane, 4–5 mm long, sometimes strongly downward-curved near the tip of the cane. Petioles with sparse to dense nonglandular hairs, armed with downward-curved prickles to 2 mm long. Stipules 6–13 mm long, linear to threadlike. Primocane leaflet margins finely to sharply toothed, the upper surface thinly hairy, the undersurface velvety hairy. Central primocane leaflets 5.0–13.5 cm long, 2.5–5.5 cm wide, narrowly elliptic, often less than 1/2 as wide as long, rounded to angled at the base, angled (or occasionally tapered) to a sharply pointed tip, the leaflet stalk about 1/10–1/4(–1/3) as long as the leaflet blade; lateral leaflets resembling but smaller than the central leaflet, the middle pair stalked, the basal pair nearly sessile. Inflorescences typically racemose or clustered, (4.5–)6.0–12.0 cm long, 3–5 cm wide, with 2–5(–11) flowers and 3–7 bracts, these typically jaggedly toothed, about evenly divided between simple bracts and those with 3 leaflets; flower and inflorescence stalks rather delicate, with nonglandular hairs and occasional needlelike or small, downward-curved prickles. Sepals 4–5 mm long, 2.5–3.0 mm wide, ovate-triangular, tapered to a sharply pointed tip or abruptly tapered to a short, slender point. Petals 7–13 mm long, narrowly obovate. Fruits 9–14 mm long, 7–12 mm wide, short cylindric. 2n=14, 21. May–June.

Scattered, mostly south of the Missouri River (southeastern U.S. west to Texas and Oklahoma). Bottomland forests, mesic upland forests, banks of streams and spring branches, swamps, ledges and tops of bluffs, glades, and upland prairies; also pastures, fencerows, margins of crop fields, and roadsides.

A white-fruited, horticultural variant, cv. ‘Crystal White’, closely resembles R. argutus, but has been recognized as a distinct species, R. louisianus A. Berger by some botanists. Specimens from Oregon and Texas Counties may represent escapes of cv. ‘Crystal White’ from cultivation, but such plants would key to R. argutus in the present treatment and can only be distinguished from the range of variation present in R. argutus when fruits are present.