How to Plant and Grow Hemlock

Of about ten species of hemlock in the world, only two—the eastern (Canadian) hemlock and western hemlock—are commonly planted in landscapes. With their soft petite needles and cascading branches, hemlock is one of the most graceful evergreen trees. Whether you employ it as a specimen tree, a hedge plant, or a living screen, hemlock is an eye-catching year-round addition to the landscape. These native trees are favorite nesting spots for wildlife, making hemlock a great plant for habitat-friendly backyards. With a mature height of 70 feet or more, they don’t fit in the average-size yard but there are also dwarf cultivars.

Where to Plant Hemlock

Plant hemlock in a location with partial to full sun (depending on the species) and well-draining, acidic soil. The shade-tolerant hemlock is especially useful for planting in the shadow of taller trees.

You can use hemlock to create a living screen on a property line or near a patio or porch. Its graceful branches will mask views in and out of your yard 12 months a year. Dwarf hemlock trees make welcome additions to foundation plantings, perennial gardens, and shrub borders where they provide an upright accent and all-season interest.

How and When to Plant Hemlock

Plant the tree in the early spring to give it as much time as possible to root before the onset of winter. Dig a hole that is as deep as the root ball and at least twice as wide. Place the tree in the center of the hole and backfill with the original soil. Tamp down the soil and water it well. Continue to water the tree weekly in the absence of rain.

Plant regular-size (non-dwarf varieties) trees 30 feet apart and trees for a hedge 6 feet apart.

Hemlock Care Tips

Hemlock is a low-maintenance tree. It is slow-growing but long-lived. It may take 250 years for the tree just to reach maturity.

Light

The light tolerance of hemlocks varies. Western hemlock is more tolerant of full sun than Canadian hemlock but they both do fine in partial shade, especially in a spot where they are sheltered from the hot afternoon sun.

Soil and Water

In addition to good soil drainage, hemlocks need acidic soil with a pH between 4.0 and 6.0. Before planting a hemlock, test your soil acidity to find out if you might need to modify it.

Moisture is equally important for healthy growth. Water the tree regularly during the first two years after planting to help it develop a strong root system. Cover the root zone with a 2-inch-thick layer of shredded bark mulch to prevent soil-moisture evaporation. Hemlock trees are sensitive to drought. Water them deeply during drought conditions and monitor them year-round for drought stress, which is evidenced by needles that turn yellow and die.

Temperature and Humidity

Hemlocks, especially Canadian hemlock, are hardy trees. They do not grow well in areas with hot and humid summers, especially where the temperature consistently exceeds 95 degrees F. They also do poorly in areas with hot drying winds.

Fertilizer

If planted in rich, fertile soil, hemlocks don’t need much fertilizer other than an annual springtime application of a granular slow-release tree and shrub fertilizer. For the amount to use, follow product label directions.

Pruning

Hemlock rarely needs pruning. If necessary to control the growth, shape the tree lightly in late spring. Damaged or diseased branches should be removed at any time of the year as soon as you notice them.

Pests and Problems

Especially when they are under drought stress, hemlocks can get a range of pests and diseases. The most serious and devastating pest affecting hemlocks is hemlock wooly adelgid, an insect native to East Asia that has no natural predators in North America. Affected trees have dry, white wooly masses on the underside of the outermost branch tips. If you detect wooly adelgid on your tree, it is key to treat it promptly with a systemic insecticide.

Types of Hemlock

Canadian Hemlock

Tsuga canadensis, also called eastern hemlock, is native to dense forests from eastern Canada south to the Appalachian Mountains to Georgia and Alabama. It is a stately tree that grows up to 75 feet tall with graceful green needles and small cones. Zone 3-8

'Gentsch White' Canadian Hemlock

This variety of Tsuga canadensis is a shrub form that bears distinctly white-tipped new growth on a rounded tree that reaches 4 feet tall and wide. Zone 3-7

‘Moon Frost’ Canadian Hemlock

‘Moon Frost’ is a variegated dwarf cultivar of Canadian hemlock reaching 2 to 4 feet in height and width when mature. New needles are white and although they darken over time, they retain a hint of white. Zone 4-7

Weeping Canadian Hemlock

This cultivar, also known as Sargent’s weeping hemlock, is a mounding shrub rather than a tree. Tsuga canadensis ‘Pendula’ has dense, deep green, finely textured foliage. It grows 5 feet tall and at least 8 to 10 feet wide. Zone 4-8 

Western Hemlock

Western hemlock (Tsuga heterophylla) can grow over 100 feet tall and 30 feet wide. Its native habitat is from Alaska to northern California all along the coast as well as in parts of British Columbia, Idaho, and Montana. It grows best in full sun but also tolerates partial shade. Zone 5-8

‘Thorsen’s Weeping’ Western Hemlock

If you let it trail on the ground, this dwarf cultivar grows only 3 to 6 inches tall and slowly spreads 1 to 5 feet. Instead of growing it as a groundcover, it can also be staked to form a cascading mound. Zone 6-8