25. Rubus laciniatus Willd. (cutleaf blackberry)

Pl. 543 e, f; Map 2523

Canes to 150 cm long and 80–120 cm tall, 3–10 mm in diameter, arching and often branched. Canes at maturity with sparse, fine hairs. Prickles moderate, 1.0–2.4 per cm of cane, 5–7 mm long, broad-based and strongly downward-curved. Petioles with nonglandular hairs, armed with many broad-based, downward-curved prickles to 3 mm long. Stipules 6–13 mm long, linear to filiform, clearly lateral, diverging (2–)3–6+ mm from the base of the petiole. Primocane leaves with 5 or more leaflets, the margins irregularly and sharply toothed and deeply incised, sometimes strongly lobed, the upper surface thinly to moderately hairy, the undersurface densely and softly hairy. Central primocane leaflets 6.0–11.5 cm long and 4–11 cm wide, ovate-triangular in general outline, angled to truncate at the base, angled ultimately to a narrow, sharply pointed tip, the leaflet stalk about 2/5–1/2 as long as the leaflet blade; lateral primocane leaflets also strongly lobed or divided but typically also ovate-triangular in general outline, stalked. Inflorescences typically paniculate, 23–58 cm long and 10–27 cm wide, with 10–40 flowers, and 4–8 leafy bracts, these concentrated at the basal nodes, a mixture of simple bracts and those with 3 or 5 leaflets; flower stalks with spreading, nonglandular hairs, inflorescence stalks zigzag, with sparse to dense nonglandular hairs, both flower and inflorescence stalks with strong downward-curved prickles. Sepals 8–13(–25) mm long, 2–4 mm wide, lanceolate, armed with small, yellowish, needlelike prickles, sometimes with leafy, jagged tips. Petals 10–12 mm long, obovate, often with 2 or 3 lobes, pale pink. Fruits 15–25 mm long, 10–25 mm wide, short-cylindrical. 2n=28. June.

Introduced, uncommon, sporadic (may be of European garden origin; widely naturalized in Europe, the U.S., and Australia). Edges of mesic upland forests; also pastures and open, disturbed areas.

This distinctive taxon appears to be represented in Missouri only by escaped or persisting populations of European horticultural selections. Steyermark (1963) also considered it nonnative in the United States.