A small genus of evergreen coniferous trees, natives of western N. America, Mexico, Guatemala, the Mediterranean region, the Himalaya and China. The leaves are always minute, scale-like and flattened to the branchlet, being superposed in four rows. The ultimate divisions of the branchlet are usually arranged irregularly, not in flattened sprays as in Chamaecyparis and most thujas. Flowers unisexual, both sexes on the same tree but in different catkins. Males composed of numerous short-stalked stamens; fruit a globose or elliptical cone composed of mushroom-shaped (peltate) scales with a ‘boss’ or enlargement in the centre; scales with numerous seeds (usually five or less in Chamaecyparis).
The hardiest of the cypresses are now considered to belong to the separate genus Chamaecyparis. Those that remain in Cupressus are nearly all somewhat tender in the average climate of Britain, the hardiest being arizonica and the allied glabra, macnabiana and macrocarpa, though bakeri, little known here at present, may prove to be as hardy as these or hardier. C. lusitanica is on the borderline, but is hardy as far east as Sussex and Surrey. They thrive in either loamy or peaty soil, well drained; and should be given a sheltered place, as they are subject to injury by wind, especially where they grow fast. Some species, notably macrocarpa and sempervirens, show two curiously diverse types of habit, viz., the horizontal-branched and the fastigiate, but most of them are, when young, of columnar or pyramidal form.
Most of the cypresses can be increased by means of cuttings, which, although probably not so good as seeds, still make good trees. All, if growing in poor soil, are benefited by applications of manure water or by top-dressings of manure. They are subject, especially in poor soils, and during a succession of dry seasons, to attacks by white scale insects. The best remedy is spraying with Malathion in March and April, when the young hatch out.
The North American species of Cupressus are studied by C. B. Wolf in El Aliso, Vol. 1, pp. 1-250 (1948).
From the Supplement (Vol. V)
The genus is reviewed by John Silba in Phytologia, Vol. 49, pp. 390-99 and Vol. 52, pp. 349-61 (1983).