These are mostly big trees with horizontal to drooping branches and an unusually graceful appearance. Needlelike leaves are banded with white beneath, flattened and narrowed at the base to form distinct, short stalks. Small, oval, medium brown cones hang down from branches. Bark is deeply furrowed, cinnamon colored to brown.
All hemlocks need some winter chill; all are shallow rooted. They do best in acid soil and high summer humidity, with protection from hot sun and wind. Hemlocks take well to heavy pruning and make excellent clipped hedges and screens. Subject to browsing deer.
T. canadensis. CANADIAN HEMLOCK. Native from Nova Scotia to Minnesota, southward along mountain ranges to Alabama and Georgia. Dense, pyramidal tree grows 4070 ft. or taller, half as wide. Tends to be multitrunked. Outer branchlets droop gracefully. Dark green, about 12-in.-long needles are mostly arranged in opposite rows on branchlets. Fine specimen tree, tall screen, or clipped hedge. 'Cole's Prostrate' is 1 ft. tall (usually less) and spreads to 3 ft. or more. 'Gentsch White', to 2 ft. high and 112 ft. wide, has white-tipped new growth. 'Jeddeloh' spreads to 34 ft. tall and 46 ft. wide, with a bird's nestlike depression in the center. 'Moon Frost' is rounded, 3 ft. high and wide, with white new growth that blushes pink in winter. 'Pendula', Sargent weeping hemlock, grows slowly to 1015 ft. tall and twice as wide, with pendulous branches; with careful pruning, it can easily be kept to handsome, 2- to 3-ft., cascading mound suitable for a large rock garden. Many other dwarf, weeping, and variegated selections are sold.
T. caroliniana. CAROLINA HEMLOCK. Native to mountains in the southeastern U.S. Resembles T. canadensis but is somewhat slower growing, a little stiffer in habit, and darker green in color. Longer needles are arranged all around the twigs instead of in opposite rows.
Easily damaged by salt and drought. Subject to various pests and diseases, but damage is not always serious if plants are well grown. A woolly adelgid (a type of aphid) is causing the decline and even death of many hemlocks in the Southern Appa- lachians. Check with your local Cooperative Extension Service for best treatment practices in your area.