Photo: Ptelea, CC BY-SA 4.0 · Wikimedia Commons

September Elm

Ulmus serotina

Also called red elm.

A rare southern elm that blooms in September and ripens fringed seed by November, a fast-growing shade tree of limestone bluffs and stream sides.

RareWildlife value

Type: Large tree
Mature height: 60–70 ft
USDA zones: 4–8
Growth rate: Fast
Sun: Full, Part
Soil moisture: Dry, Average
Grows wild in: Rocky ground, stream banks, rich moist slopes and floodplain forests
Native range: 8 states, north to Illinois, south to Georgia and west to Oklahoma
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Alabama, Arkansas, Georgia, Illinois, Kentucky, Mississippi, Oklahoma and Tennessee
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September elm is one of the two native elms that flower in the fall. It has the general form of American elm, but its branches are smaller, somewhat drooping and often corky-winged. It is never abundant, and it is easily mistaken for other elms. NatureServe ranks it critically imperiled in Georgia and Oklahoma and imperiled in Mississippi, and Kentucky lists it as a species of special concern. Grow it as a shade tree on a limestone slope or beside a stream, where its autumn flowers and seed can be watched.

Size, growth and what to expect

September elm grows fast, about 2.75 feet a year in our growth estimator. PLANTS puts it at up to 30 feet at 20 years. It reaches 60 to 70 feet with a spreading, rounded crown and a trunk 2 to 3 feet through.

The flowers open in September, in slender hanging clusters, and the samaras ripen in late October or early November. Each is about half an inch long, deeply notched at the tip and fringed with white hairs. Birds and small mammals, squirrels among them, eat the seeds.

It grows wild in scattered stands from southern Illinois across Kentucky and Tennessee to north Georgia, Alabama and Mississippi, and west to Arkansas and eastern Oklahoma. It is most common in Arkansas and Tennessee, and few stands are known outside Tennessee. Its sites are limestone bluffs, stream sides, rich woods and upland coves.

How to grow September Elm

September elm grows in full sun or light shade on a moist soil that drains well, from clay loam to sandy loam. It also grows on dry, rocky limestone soils, but not on poorly drained lowland, where it is absent in the wild. Plant it 30 feet from a wall and more than 50 feet from overhead wires, and set trees 40 feet apart.

Saplings ship bare-root or potted. Plant them dormant, from leaf fall until bud swell, in a hole wider than the roots and no deeper. Set the root flare at the soil line, put the native soil back in, and keep the mulch clear of the trunk. Sow the seed outdoors in late fall, no deeper than a quarter inch, and seedlings come up in spring. For spring, hold it damp in the refrigerator for 60 to 90 days first.

Water weekly through the first summer. Deer browse the twigs and buds, so guard young trees for the first few years. Keep one leader as it grows.

September elm carries both male and female parts in each flower, but elms seldom set seed with their own pollen, so plant two or more seedlings from different parents for seed. Dutch elm disease is the great danger. It has killed all three mature September elms at the National Arboretum since 1965, and seedlings are very susceptible too. It is also a host of American mistletoe.

Heights and zones are typical ranges for the species in cultivation; local conditions and seed source shift them.

Sources (11)