3. Morus rubra Linnaeus, Sp. Pl. 2: 986. 1753.
Red mulberry, mûrier rouge, moral
Morus rubra var. tomentosa (Rafinesque) Bureau
Shrubs or trees , to 20 m. Bark gray-brown with orange tint, furrows shallow, ridges flat, broad. Branchlets red-brown to light greenish brown, glabrous or with a few trichomes; lenticels light colored, elliptic, prominent. Buds ovoid, slightly compressed, 3-7 mm, apex acute; outer scales dark brown, often pubescent and minutely ciliate; leaf scars oval to irregularly circular, bundle scars numerous, in circle. Leaves: stipules linear, 10-13 mm, thin, pubescent; petiole 2-2.5 cm, glabrous or pubescent. Leaf blade broadly ovate, sometimes irregularly lobed, 10-18(-36) × 8-12(-15.5) cm, base rounded to nearly cordate, sometimes oblique, margins serrate or crenate, apex abruptly acuminate; surfaces abaxially sparsely to densely pubescent or puberulent, adaxially with short, antrorsely appressed trichomes, usually scabrous. Catkins: peduncle pubescent; staminate catkins 3-5 cm; pistillate catkins 8-12 × 5-7 mm. Flowers: staminate and pistillate on different plants. Staminate flowers: sepals connate at base, green tinged with red, 2-2.5 mm, pubescent outside, ciliate toward tip; stamens 4; filaments 3-3.5 mm. Pistillate flowers: calyx tightly surrounding ovary; ovary green, broadly ellipsoid or obovoid, slightly compressed, 1.5-2 × 1 mm, glabrous; style branches divergent, whitish, sessile, ca. 1.5 mm; stigma papillose. Syncarps black or deep purple, cylindric, (1.5-)2.5-4(-6) × 1 cm; fleshy calyx surrounding achenes; achenes yellowish, oval, flattened, ca. 2 mm, smooth.
Flowering spring-summer. Moist forests and thickets; 0-300 m; Ont.; Ala., Ark., Conn., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Md., Mass., Mich., Minn., Miss., Mo., Nebr., N.J., N.Y., N.C., Ohio, Okla., Pa., S.C., Tenn., Tex., Vt., Va., W.Va., Wis.
Morus rubra is sporadically established along fencerows in southern New Mexico (R. Spellenberg, pers. comm.). Rhode Island is in the range of Morus rubra , although I do not know of any documented specimens.
Morus rubra is a common tree of eastern North America. The leaves are highly variable, often with deeply lobed and entire leaves on the same plant. The abaxial surface of the leaf varies from sparsely to densely pubescent.
According to D. E. Moerman (1986), Native American tribes used infusions of the bark of Morus rubra medicinally to check dysentery, as a laxative, and as a purgative; infusions of the root for weakness and urinary problems; and tree sap rubbed directly on the skin as treatment for ringworm.