4. Ulmus rubra Muhlenberg, Trans. Amer. Philos. Soc. 5: 169. 1793.
Slippery elm, orme rouge
Ulmus crispa Willdenow; U. fulva Michaux; U. pendula Willdenow; U. pubescens Walter
Trees , 18-35 m; crowns open. Bark brown to red, deeply and irregularly furrowed. Wood soft. Branches spreading; twigs gray, densely pubescent when young, glabrous with age. Buds obtuse; scales red, margins red-tomentose. Leaves: petiole 5-7 mm, pubescent. Leaf blade obovate to ovate, 8-16 × 5-7.5 cm, base oblique, margins doubly serrate in distal 1/2-3/4, singly serrate proximally, basal teeth 6 or fewer, rounded, less distinct, apex acuminate; surfaces abaxially tomentose, dense tufts of white hair in axils of major veins, adaxially harshly scabrous, trichomes pointed toward apex, margins ciliate. Inflorescences dense fascicles less than 2.5 cm, 8-20-flowered, flowers and fruits not pendulous, subsessile; pedicel 1-2 mm. Flowers: calyx green to reddish, shallowly lobed, lobes 5-9, reddish pubescent; stamens 5-9; anthers reddish; stigmas exserted, pink reddish. Samaras yellow to cream, suborbiculate, 12-18 mm diam., broadly winged, samaras pubescent on body only, rusty-tomentose, margins glabrous. Seeds thickened, not inflated. 2 n = 28.
Flowering late winter-early spring. Lower slopes, alluvial flood plains, stream banks, riverbanks, and wooded bottom lands; 0-600(-900) m; Ont., Que.; Ala., Ark., Conn., Del., D.C., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Nebr., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Okla., Pa., S.C., S.Dak., Tenn., Tex., Vt., Va., W.Va., Wis.
Scabrous-leaved Ulmus rubra is often confused with U . americana . Where ranges coincide, U . rubra may freely intergrade with Ulmus pumila Linnaeus, a widely introduced species.
The red-rust, mucilaginous inner bark of Ulmus rubra is distinctive; its sticky slime gives this tree its common name of slippery elm. Native American tribes used Ulmus rubra for a wide variety of medicinal purposes, including inducing labor, soothing stomach and bowels, treating dysentary, coughs, colds, and catarrhs, dressing burns and sores, and as a laxative (D. E. Moerman 1986). Various preparations utilizing it are still marketed.