The Encyclopedia Americana (1920)/Elm

ELM, Ulmus, a genus of trees and a few shrubs of the family Ulmaceæ. The species, of which about 20 are known, are natives of the North Temperate zone and the southern portions of the Arctic zone. Their southern limits seem to be the Himalayas in Asia and the mountains of southern Mexico. None are natives of the Pacific slope of North America. They are characterized by short-petioled, alternate, rough, usually deciduous leaves with serrate edges; axillary racemes of perfect, apetalous flowers which appear in early spring before or with the leaves; and compressed, winged, dry fruits. Many of the species are of wide economic importance. Their hard, heavy, tough, pliable wood is largely used in the manufacture of barrels, agricultural implements, boats, wagon wheels, buildings, etc., and for fuel. The inner bark of some species furnishes an article of food, and that of others a tough

bast fibre used for cordage and cloth making. The outer bark of some is used in dyeing and sugar refining. Various parts of several species were formerly popular remedies employed in medicine, but except in domestic and local practice are rarely prescribed. Most of the species are highly valued as ornamental trees in street and park planting, those specially popular being the straight-trunked, tall-growing, vase-formed species, which quickly over-arch the streets and cast an abundant shade. Many cultivated varieties of fantastic form, color of foliage, or habit of growth are also planted as curiosities.

The best known American species is the white, water, or American elm (U. americana), which grows in rich moist woods, especially on the shores of streams, from Newfoundland to Florida and westward to the eastern side of the Rocky Mountains. It is a tall tree, often attaining a height of 120 feet when growing in the forest, and with a wide-spreading, less lofty top when growing in the open, where it may be seen in several different forms, popularly known as vase, plume, oak-tree, etc., according to the arrangement of the branches. Some specimens of each one develop numerous twiggy growths upon the trunk and main branches, which are thus rendered very attractive because of their feathery appearance. The most common form is the vase, in which the main branches develop at about 20 feet or more, and at their bases gradually, and toward their extremities widely diverge. This is probably the most popular street form in America. Another well-known American species is the slippery or red elm (U. fulva), which attains a naght of 70 feet in rich soils and is found from Quebec to Florida and westward to Texas and the Dakotas. It is called red because the bud scales are reddish and conspicuous when unfolding in spring; and it is called slippery because of its mucilaginous inner bark. Its wood is less valued than that of the Elnglish elm, but more than that of the white elm. The cork or rock elm (U. racemosa), which grows on river banks from New England to Nebraska and as far south as Kentucky and Tennessee, attains a height of 100 feet and is noted for the corky developments resembling wings on the smaller branches. Its wood is specially valued for its great durability, strength, pliability and toughness. Another species with corky, winged branches is the wahoo or winged elm (U. alata), which ranses from Virginia to Florida and westward to Texas and Illinois. It rarely exceeds 70 teet in height, is very attractive in habit, and is planted for ornament in the South, but not in the North, as it is not sufficiently hardy for the rigors of winter.

The most noted European species is the English elm (U. campestris), which ranges through middle and southern Europe, northern Africa, and eastward to Japan. It reaches 100 feet in height and has a rather round-topped or open head, on account of its spreading branches. It is frequently planted for ornament at home and abroad, and in America is valued because its foliage continues green for several weeks after that of the white elm. It has several distinct varieties, which are sometimes considered as distinct species, and of which there are a large number of horticultural varieties. The next most important European species is probably the Scotch or wych elm (U. scabra),

which has much the same range as the preceding species, like which it attains a height of about 100 feet. It is a variable species with many cultivated varieties, one of the best-known of which is the Camperdown elm, which has long, pendulous branches, on account of which the tree is frequently planted as a curiosity in parks and gardens. The Chinese elm (U. parvifolia) is a semi-evergreen shrub or small tree, a native of eastern Asia, which has proved hardy in America as far north as Massachusetts.

Elms are readily propagated from seed which ripens in late spring or early summer and should be sown at once. The seedlings are easily managed, both as to cultivation, transplanting and pruning. The trees do best in rich soil, especially if moist. The choice varieties are generally grafted. The trees, especially of the American or white elm, are specially liable to the attacks of certain insects and diseases, which often defoliate them. Tbc latter may be kept in check by the timely and proper application of a standard fungicide (q.v.).

The name elm is also given to various unrelated trees, the best-known of which are probably the following: Water elm (Planera aquatica); Spanish elm or Bois-de-Chypre (Cordia gerascanthus). Several Australian trees are also known as elms, especially Duboisia myoporoides and Aphananthe philippinensis, each of which is valued for its timber.