Ulmus americana is a tree to 40 m; 130 cm dbh; 200 yrs; root depth variable with soil moisture, roots associated with VA mycorrhizae (Brundrett and Kendrick 1988); bark gray, interlacing fissures; vase shaped habit, trunk divides low; twigs and leaf buds relatively hairless, buds smooth to slightly pale hairy, less than 0.6 cm long, scales pale brown with dark edges.
Leaves alternate, stalk to 0.8 cm long, blade 8-14 cm long, doubly toothed, base unequal, smooth to slightly rough above, sometimes hairy below; leaves expand early May; winter plant leafless 166 days (Britton 1874).
Flowers greenish, calyx reddish, in tassels, stigmas white, anthers red, (Rehder 1986) wind pollinated; blooms March.
Fruit dry, 1-seeded, flat, winged, margin hairy, 1 cm, tip deeply notched, wind dispersed, April-May. Seeds eaten by birds and mammals (Martin et al. 1951). Seed germinates soon after dispersal or the following spring.
Wetland status: FACW-.
Frequency in NYC: Frequent.
Habitat: Pioneer on moist to wet soil, second growth, old fields, flood plains. Soil pH 5-8 (USDA, NRCS 2010). Tolerant of drought and heat. Moderately tolerant of flooding, salt, soil compaction and shade, index 6.4 (Hightshoe 1988). Buds and twigs eaten by rabbits (Martin et al. 1951). Saplings persist under light shade of other pioneer species.
Notes: Young trees stump sprout if cut. Population limited by Dutch elm disease caused by the fungus, Ceratocystis ulmi (Ascomycotina). Fungus transmitted by sap feeding elm bark beetles, Scolytus multistriatus and Hylurgopinus rufipes. Dutch elm disease causes wilting, yellowing, death of foliage and eventually of tree. Mortality also caused by elm yellows (also called phloem necrosis). This is caused by mycoplasma like organisms (MLOs) that are transmitted by the white-banded elm leafhopper (Scaphoideus luteolus) or by root grafting. Infected trees have yellowing, drooping foliage, leaf drop followed by death of tree within weeks of infection. Virticillium albo-atrum (Deuteromycotina), a soil fungus, also kills trees. Trees attacked by many insects, leaf miners, wood borers, and leaf eaters such as forest tent caterpillar (Malacosoma disstria, Lasiocampidae); larvae of the question mark butterfly (Polygonia interrogationis), mourning cloak (Nymphalis antiopa, Nymphalidae), polyphemus moth (Antheraea polyphemus, Saturniidae), imperial moth (Eacles imperialis, Saturniidae), four-horned/elm sphinx moth (Ceratomia amyntor, Arctiidae), banded tussock moth (Halysidota tessellaris), white-marked tussock moth (Orgyia leucostigma, Lymantriidae), yellow-necked caterpillar moth (Datana ministra, Notodontidae), large tolype moth (Tolype velleda), Lepidoptera (Covell 1984; Opler 1992; Tallamy 2003), and the elm leaf beetle, Pyrrhalta luteola. Elm bladder galls caused by the mite Eriophyes ulmi, makes small pointed leaf galls. Cockscomb galls, caused by the aphid Colopha ulmicola, are corky (Burns and Honkala 1990; Johnson and Lyon 1991; Sinclair et al. 1987). A host tree of the Asian longhorn beetle, Anoplophora glabripennis (see Norway maple).