Ulmus

The American elm is the great vase-shaped shade tree that once arched over Main Streets and town commons across eastern North America - a fast, extremely cold-hardy deciduous tree of 60 to 80 feet whose upright trunk divides into a fountain of high, spreading limbs that meet overhead to form a living cathedral ceiling. That iconic form, and the species' tolerance of wet soil and tough urban conditions, made it the default American street tree for a century. Then Dutch elm disease (DED) - an introduced fungal disease carried by elm bark beetles - swept through in the 20th century and killed the vast majority of mature street and shade elms across the continent. The honest reality for a gardener today is blunt: do not plant the unselected wild species expecting it to survive. If you want the American-elm form, plant a DED-tolerant cultivar bred and selected for resistance - 'Princeton', 'Valley Forge', 'New Harmony', or 'Jefferson' - and say so plainly. Where it does grow, it is fast, hardy to USDA zone 3, and remarkably forgiving of wet ground and city stress.

An East Asian elm, also called lacebark elm, planted across North America as a tough street, shade and bonsai tree: small glossy leaves, a rounded crown of long drooping branches, bark that flakes into patches of grey, cream, orange and green, and good resistance to Dutch elm disease. It flowers and seeds in late summer and fall, and it self-seeds: it has naturalised in several US states and is listed as invasive in others, so NC State Extension asks gardeners to plant a native tree instead.

The native elm of moist bottomlands, stream banks and rich woods across eastern North America: a coarse, vase-shaped to round-crowned tree with sandpapery leaves, red-hairy winter buds and the slimy, sweet red inner bark that gives it its name. Smaller and rougher than American elm and also susceptible to Dutch elm disease, it is a tree for naturalized ground and wildlife plantings rather than a street or lawn.