Carolina Hemlock

Size, growth and what to expect

Carolina hemlock grows slowly, about a foot a year in our growth estimator. It makes a narrow pyramid 40 to 60 feet tall and 20 to 25 feet wide. It begins to bear seed at about 20 years, and good crops come at 25 to 30. The oldest tree dated by its rings, in North Carolina, was 307 years old.

Its cones are 1 to 1.5 inches long, longer than the eastern hemlock's, and their scales spread wide when ripe. Pollen is shed in March and April, and the cones ripen in August and September. Birds and mammals eat the seed.

It grows wild only in the southern Appalachians, from southwest Virginia and east Tennessee to the mountains of the Carolinas and north Georgia. Most stands lie between 2,100 and 4,000 feet. In western North Carolina, hemlocks had about an even chance of surviving 12 years after the adelgid reached their county.

How to grow Carolina Hemlock

Carolina hemlock does best in part shade in a cool, sheltered spot, and it takes full shade. In sun it needs shelter from wind and hot weather, which scorch the foliage. It wants an acid soil that stays moist but drains well, and it does not stand drought. Plant it 15 feet from a wall, and set trees 15 feet apart for a screen. Keep it more than 50 feet from overhead wires.

Saplings ship bare-root or potted. Plant in early spring or early fall, in a hole wider than the roots and no deeper. Set the root flare at the soil line, put the native soil back in, and mulch a wide ring clear of the trunk. Seed needs one to three months of cold, damp storage in the refrigerator. Sow it in spring, barely covered, in a bed with light shade. The seedlings are small and burn in hot sun their first summer.

Water weekly through the first two summers and in every long dry spell after that. The roots are shallow, so keep a mulch of leaves or bark over them. Deer browse the foliage now and then in winter, so cage young trees where deer are many. It takes clipping as a hedge, and a specimen needs pruning only of dead wood.

Carolina hemlock carries male and female cones on the same tree and sets seed with its own wind-borne pollen, so one tree bears alone. The hemlock woolly adelgid, a tiny sap-sucking insect hidden under white wool on the twigs, is its gravest threat. An infested tree usually loses its needles and dies within a few years unless it is treated. Imidacloprid applied to the soil beneath the tree gives good control, and such systemic treatments suit trees away from water. Horticultural oil and insecticidal soap sprays also control it, though oil can damage hemlock in the growing season, especially in dry weather.