Flower:

Dense, round clusters ¾ to 1 inch across from lateral buds on 1-year-old branches, each with 10 to 20 flowers and appearing before leaves emerge. Flowers have no petals, the green to reddish, cone-shaped calyx is hairy, only about 1/8 inch wide with 5 to 8 rounded, papery lobes. In the center is a 2-parted, pinkish-red, feathery style and 5 to 8 erect, white stamens that are at least twice as long as the calyx, the stamen tips initially reddish-purple turning purplish black. Flower stalks are hairy and less than 1/8 inch long.

Leaves and bark:

Leaves are simple and alternate, oval-elliptic to obovate (widest above the middle), 3½ to 7 inches long, 2 to 4 inches wide, abruptly tapered to a pointed tip, rounded and asymmetrical at the base, on a short, hairy stalk. Edges are double-toothed with roughly half the veins forking towards the tip (easily seen on the underside). The upper surface is medium to dark green with stiff, short hairs making it rough to the touch, the lower surface light green with similar stiff hairs though not as rough to the touch, and dense tufts of hairs in vein axils.

Young twigs are hairy and initially green, turning gray to gray-brown. Buds are up to ¼ inch long, elliptic, hairy at the tip, with hairy, dark brown to blackish scales; flower buds are larger, round, densely covered in rusty-colored hairs.

Older branches are hairless with gray bark. Older bark has ridges and furrows that are somewhat shallow and generally running parallel. Trunks are up to 35 inches diameter at breast height.

Fruit:

Fruit is a winged seed called a samara: flat, egg shaped to somewhat oblong, 1/3 to ¾ inch long, hairy only in the center directly over the seed, and the remnant styles often persistent at the tip.

Notes:

Red elm is a large forest tree, restricted mostly to the southern 2/3s of Minnesota, typically in more upland sites. The inner bark is sticky and a bit slimy, hence the other common name, Slippery Elm. While never as common as American Elm (Ulmus americana), its populations were also devastated by Dutch Elm Disease and today it is somewhat scarce. It certainly does not have the regeneration of American Elm and, while very similar, it can be distinguished by its round, button-like clusters of nearly stalkless flowers, leaf veins that frequently fork towards their tips and short, soft hairs on the fruit surfaces but not around the edges. The flower clusters much resemble those of the non-native Siberian Elm (Ulmus pumila), which are about half the size of Red Elm and have creamy yellowish styles, not red. These two species do hybridize, resulting in trees with intermediate characteristics.