elms

Ulmus is a large genus of deciduous trees. It occurs throughout the temperate regions of the Northern Hemisphere.

There are 35 Ulmus species worldwide, 10 species in North America north of Mexico, and 4 species in Minnesota. Three of the species in Minnesota are native, one is naturalized. Three additional species occur in the state but are not naturalized. Ulmus parvifolia has been widely planted in hedgerows and groves in the Midwest. Ulmus glabra and Ulmus procera have been planted as ornamentals in parks and residential yards.

Elms are important components of hardwood forests. They have been widely planted as ornamental trees and shade trees on streets, in parks, and in gardens. They are easy to propagate by seed, are fast growing, and are moderately shade tolerant. They occur in both wet and well drained soils.

Dutch Elm disease has decimated elm populations in Europe and North America. Elm trees on streets and in fields have been killed by the disease. It is controlled in cities to a limited extent by the prompt removal of diseased trees. Of the species occurring in Minnesota, only Siberian elm is resistant to the disease.

The four elm species in Minnesota are all large or medium-sized trees.

The trunk is often forked below the crown. Side branches are produced in two rows. They are spreading and often arched. Twigs are slightly zigzagged. The pith is solid and round in cross section.

The leaves are deciduous, alternate, undivided, and unlobed. The blade is oval, thick, and tapered to a sharp point at the tip. The base on most species is asymmetric. The margins are doubly toothed. The veins are straight and prominent, and they end in a large tooth. Whether veins are forked, and how many are forked, are important features in determining the species.

The flowers are small and inconspicuous. They appear in groups of 3 or 4 before the leaf buds open.

The fruit is a winged, one-seeded, seed case (samara). The samara is flattened, papery, and oval or almost round. It matures and falls away in the spring before the leaves reach full size.

Sources

2, 3, 4, 5, 7, 8, 22, 24, 28, 29, 30.

Location: Fairview Twp.