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Essential Tips on How to Grow and Care for Canadian Hemlock Trees

How to Grow and Care for Canadian Hemlock Trees
You may plant a Canadian hemlock as a specimen in your garden, or you can create a unique hedge with these trees. We provide hemlock tree facts and some valuable information on hemlock tree care.
Leena Palande
Last Updated: Jul 28, 2017
Did You Know?
The Eastern Native Tree Society (ENTS) discovers and measures the height, diameter, and trunk volume of very large Canadian hemlock trees. The trunk volume of the tree which is believed to be the largest natural evergreen conifer in the eastern United States was 44.8 m3.
A Canadian hemlock is known for its graceful, drooping, evergreen foliage and long life. This slow-growing tree may take 250 to 300 years to reach maturity. Trees more than 450 years old have been seen producing excellent cones. The trees may live for 800 years or more, and they can be very tall and large.

Although it takes some effort to grow this tree, it's well worth it. Once established, hemlocks require little care. They are particularly suitable for wooded areas. You can plant them near streams, as they look natural in such environment. These long-lived trees are gorgeous additions to the landscape. If you have limited space, you can use shorter shrub forms as foundation plants. When planted along the shady part of your home near rhododendrons (another shade lover), they can help enhance the beauty of your garden.
Different Cultivars
Over 300 cultivars of Canadian helmock have been developed for landscape usage. Dwarf forms and shrubs are especially developed for circumstances in which growing a tall tree is not possible. A shrub is equally graceful and attractive. Timely pruning plays an important role in the height and width of the shrubs. 'Pendula', the popular upright weeping form grows to about 5-15 feet tall and wide. Another dwarf form, 'Horsford Contorted' comes with twisted branches.
'Cole's Prostrate' can be used as a 'groundcover', because this creeping plant grows only 1-foot tall. 'Sargentii', a popular large weeping shrub (can be 3 m tall and 6 m wide), has numerous pendulous branches, and looks beautiful when planted near water or in rock gardens. 'Jeddeloh' is similar to the popular bird's nest spruce. 'Aurea Compacta' has yellow needles.
How to Grow Canadian Hemlocks
Canadian Hemlocks
➺ The trees should be planted at the beginning of spring. This is the best time of year to plant the trees. Do not plant them in winter or summer. The tree is weak and vulnerable during its early growth. Excessive heat and cold can damage and kill the tree.
➺ Do not plant it very close to the house or fence. Its growing roots can damage the structure. As the tree grows taller, the roots need enough room to spread so that they can support the tree. Leave adequate space between two trees, if you are planting several trees.
➺ The tree prefers partial shade; however, it can tolerate full shade. It is an easy-to-grow tree.

➺ The soil can be slightly acidic to neutral.
➺ To maintain its evergreen foliage, the tree needs plenty of water. It loses water during winter (winter drying). Cold or frozen soils make it difficult for roots to replenish moisture as fast as it is lost. The tree should be watered regularly during the late fall. Dehydration can kill the tree. It starts conserving water during late autumn. At that time, it should be watered carefully. Proper mulching during this period will help the tree survive winter. The tree thrives in organically rich soil.
Canadian Hemlocks
➺ Once established, water the tree twice a week. See to it that the soil is well-drained and moist. As the tree is susceptible to root rotting fungi, avoid over-watering.

➺ The trees grow very slowly. They grow well in sun as well as in shade; however, the former exhibit slower growth than the latter.

➺ If the soil is very sandy or if you are planting the tree in heavy clay soil, add some composted material and peat moss to the soil.
➺ Protect the seedling from strong winds. Its shallow roots would not be able to support it, and it would topple easily. Taking care of establishing hemlocks can be a challenge. Once established, they don't require much attention.

➺ If the soil is dry and if the site is elevated, let the base of the tree be surrounded by a thick layer of mulch. A drip irrigation system can help maintain the greenery of the tree.
➺ No fertilizers are required at the time of planting and also during the initial stage of growth. They may injure new roots. Evergreen trees should not be provided with fertilizers until they are well-established. Plants that exhibit good growth and color, usually don't need fertilizer. Various types of infestations, diseases, poor drainage, or infertile soil can weaken the plants. These plants may need fertilizers. If necessary, they can be applied between mid-October and mid-March.
➺ If you want to create a barrier, trim the top and the bottom of the tree. This would encourage the growth of the sides which eventually would fill in the gap, interlocking with trees on either side. Once they fill in the gap, trim the sides (front and back) as well. The spacing may vary according to the purpose intended.

➺ Do not prune the tree for at least five years. Too early pruning can affect its growth seriously.
➺ Pruning should be done in early March or April, before the new leaves emerge. The tree responds well to pruning.

➺ You may have to prune the tree for vehicular or pedestrian clearance beneath the canopy. As this large tree doesn't lose its lower limbs (although it grows quite tall), it is ideal as a sheared or unsheared hedge.
Common Threats
Canadian Hemlocks near road
➺ The tree cannot withstand waterlogged soil. Excessive wetness can result in root rot and bark splitting. It cannot tolerate very dry soil too.

➺ The tree should not be planted roadside if de-icing salt needs to be spread on the road during winter. The leaves cannot withstand salt spray.

➺ It cannot tolerate exposure to heavy winds and urban stress.
➺ It is likely to be attacked by the hemlock woolly adelgid, a small, aphid-like, sap-sucking bug. A wooly sac covers its body. Woolly adelgid and scale infestations can prove to be life-threatening for the plant. The tallest tree that was found in the Great Smoky Mountains National Park, was killed by the hemlock woolly adelgid. The tree can also be attacked by weevils, bagworm moths, mites, other sapsuckers and woodpeckers. Regular inspections (at least once a year) of your hemlock will help prevent serious damage from pests. You may use insecticidal soap or horticultural oil to treat and get rid of these pests. The insecticide 'Imidacloprid' is recommended where adelgids are a constant threat. Consider using it as a yearly treatment, preferably in October.
➺ The tree may suffer from sun scorch if the temperatures reach 95°F. The ends of the branches may turn yellowish.

➺ Plants growing in full shade will be relatively thin and will not produce the characteristic screening effect. Those in full sun or partial shade can give the best result.
Canadian Hemlock Tree Facts
Canadian Hemlocks tree
Scientific Name: Tsuga canadensis

Common Names: Eastern hemlock, Canada hemlock, hemlock spruce, or Pruche du Canada

Type: Coniferous tree

Family: Pinaceae

Native Range: Eastern North America

Zone: 3 through 7

Average Height: about 31 meters (100 feet)

Highest Recorded Tree: 53 meters (173 feet), it was in the Great Smoky Mountains National Park
Average Diameter of the Trunk: At breast height, it can be about 1.5 meters (5 feet)

Widest Recorded Trunk: 1.75 meters (6 feet)

Spread: 30 feet

Average Leaf: 15 to 20 mm (0.6 to 0.9 inches) long

Bark: Brown and scaly, Aged trees have deeply fissured barks

Crown Shape: Pyramidal.

Stem: Straight, rarely forked

Sun: Full sun to shade

Predator: Hemlock woolly adelgid (Adelges tsugae), a sap-sucking bug
Growing Temperature: At temperatures ranging from 7° to 18° C (44° to 64° F), chances of germination are high.

Climate: Cool and humid

Water: Trees growing in full sun require a consistent supply of moisture and good drainage.

Soil: Moist, loam, sand, well-drained, slightly acidic soil

Maintenance: Medium

Foliage: Fine-textured, evergreen, drooping to the ground
Flower: Inconspicuous, green, yellow flowers, rounded 3/4" long cones

Fruit: Dry, hard, oval, brown, 0.5 - 1 inch in length

Growth Rate: Slow, 4"-10" avg per year

Special Feature: The leaves are, in fact, fine-textured evergreen needles.

Uses: Specimen, screen to break wind, for shade, or for privacy, bonsai, as hedges to mark a boundary line, etc.

Does Not Tolerate: Winds and drought
Like willows, hemlocks are riverbank trees and are important for ornamental planting. Being larger in size, they provide shelter to smaller plants and protect them from drying winds. Earlier, the bark of this tree was used to tan sheepskins and heavy leather for shoes. These days, the wood is used in the pulp and paper industry. It should be kept in mind that several species of wildlife (plants, animals, insects, and birds) dwell in the habitat provided by a dense, tall, long-lasting hemlock. We have no right to destroy their habitat. Conservation of nature is beneficial for both human beings and animals.