Mostly hardy, leaf-losing trees or large shrubs native to Europe, eastern Asia, the Himalayas and North and Central America; they belong to the Birch family, Betulaceae. They range in height from 15-80 ft., the trees usually having short trunks, and the wood is very hard and durable. The name Carpinus is a Latin word used by Pliny.
Hornbeams grow fairly quickly when planted in well-Cultivated ground but otherwise develop slowly. The European Hornbeam and some of its varieties, and the Japanese, Chinese and American Hornbeams are interesting trees for large lawns and for the fringes of woodlands. Male and female flowers are borne separately, though both are on the same tree. The male catkins are pendulous, greenish-yellow, the female catkins are erect and shorter at first but they gradually elongate and become pendulous. The ribbed, nutlike fruits enclosed in large bracts ripen in autumn.
When to Plant and Sow Seeds. The Hornbeams thrive best in an open sunny position, in deep moist loam, but they will grow in any soil, including those formed of limestone. They are planted either in spring or early fall. Propagation is by seeds sown when ripe in autumn in a cold frame or in a sheltered border out of doors; by layering the lower branches in spring; or, in dealing with rare and uncommon kinds, by grafting on seedlings. Seeds germinate irregularly, sometimes not producing plants until the second year.
Pruning may be done in August or in autumn after the fall of the leaves; it consists of thinning the branches of young trees when too many are growing from the main trunk, and thinning or shortening the branches near the tops of young trees so that each tree has a distinct and straight leading shoot.
Hornbeam Hedges. Carpinus Betulus, native to Europe and Asia Minor, grows from 40-75 feet high. With its ribbed or fluted and usually short trunk and upright branches, it is a beautiful specimen for park planting. It makes a useful thick and tall hedge for boundary and shelter.
Of numerous varieties of C. Betulus the following are the most distinct and useful: asplenifolia, deeply lobed, fernlike leaves; columnaris, a compact and erect-growing tree; incisa, with deeply toothed small leaves; pendula, a graceful weeping form; purpurea, young leaves purplish; and pyramidalis, an upright growing tree.
Carpinus caroliniana, the American Hornbeam or Blue Beech, is a bushy headed tree 2040 ft. high, having leaves which take on beautiful orange-yellow tints before they fall in autumn. It is a handsome tree but it stands pruning and shearing less well than C. Betulus.
C. cordata, a 30-40-ft.-high native of Japan, Asia and northern China, is notable for its large cordate leaves; the variety chinensis, introduced by Wilson from eastern Szechuan in 1901, has smaller leaves and hairy young shoots.
C. laxiflora variety macrostachya, a graceful tree said to reach a height of 40 ft. in western and central China, was first introduced in 1900 by Wilson; as the new leaves develop, they are of rich red color. C. Tschonoskii, a graceful shrubby tree from Japan, Asia and northern China, 20-40 ft., has corrugated leaves.
Economic Uses. The wood is used in the manufacture of agricultural implements.