tsuga
( SOO - guh )
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At-A-Glance InformationCommonly called Hemlock, this genus of evergreen trees is native to North America and Japan. These trees need full sun to partial shade and regular water, and have shallow roots. Branches are horizontal to drooping and green needles are banded with white on the undersides. Brown cones hang down from branches; bark is deeply furrowed. Hemlock needs some winter chill to perform well, but otherwise are great lawn or background trees. Although these trees are called Hemlock trees, they are not poisonous or related to the poisonous Hemlock plant.
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tsuga Species and Varietals
The genus Tsuga is a member of the plant family Pinaceae and includes between 8 and 10 species. Tsuga growing zones vary depending on the species; for more information, see the descriptions below. To find your zone, click here: Zone Map.
Tsuga canadensis (Canada Hemlock, Eastern Hemlock, Eastern Hemlock-Spruce, Pruche du Canada)
This species is native to eastern North America and reaches 40-70 feet tall and about half as wide. Tends toward a multi-trunked form. Needles are dark green; tree is dense and pyramid-shaped. Great lawn or background tree, and can also be clipped into a hedge. Commonly grown varieties are listed below.
This species is native to eastern North America and reaches 40-70 feet tall and about half as wide. Tends toward a multi-trunked form. Needles are dark green; tree is dense and pyramid-shaped. Great lawn or background tree, and can also be clipped into a hedge. Commonly grown varieties are listed below.
'Pendula'
(Sargent Weeping Hemlock) To 5 feet tall and 10 feet wide, with pendulous branches. |
'Cole's Prostrate'
1-2 feet tall and 3 or more feet wide. Bark is gnarled. |
'Gentsch White'
3-4 feet tall and just as wide, with white-tipped new foliage. |
'Jeddeloh'
3-4 feet tall and 4-6 feet wide, with a depression in the center. |
'Moon Frost'
3 feet tall and wide, with a rounded head and white new foliage that tints pink in cool weather. |
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Tsuga chinensis (Taiwan Hemlock, Chinese Hemlock) This species is native to China, Taiwan. and Vietnam, and has many recognized varieties. These large trees have blackish-brown bark and green foliage. |
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Tsuga diversifolia (Northern Japanese Hemlock) This species is best in zones A2, A3, 2-7 and 17 and is native to northern Japan. It slowly reaches 35-60 feet tall and 25 feet wide, with a multi-trunked habit and graceful, sweeping branches. Needles are short and dark green. This species is more tolerant of wind and frost than other Hemlocks. Variety 'Loowit' reaches 1-1.5 feet tall and 2 feet wide, with bright green, stout needles. |
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Tsuga dumosa (Himalayan Hemlock, Yunnan Tieshan) This species is native to the eastern Himalayas (India, Nepal, Bhutan, Myanmar, Vietnam and Tibet). It is occasionally grown as a landscape ornamental in large gardens |
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Tsuga heterophylla (Western Hemlock, Western Hemlock-Spruce) This species grows well in zones A2, A3, 2-7 and 14-17 and is native to Alaska down to Northern California, east to Idaho and Montana. They have a narrow pyramid shape and drooping branches. Foliage is dark green to yellow-green and fernlike, and these trees top out at 70-130 feet tall and 20-30 feet wide. Variety 'Thorsen's Weeping' a prostrate form that can serve as a groundcover or staked when young to be a weeping small tree. |
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Tsuga mertensiana (Mountain Hemlock) This species grows well in zones A1-A3, 1-7 and 14-17 and They are native to Alaska's mountains down to the Sierra Nevada Mountain Range in California and east to north Idaho and Montana. These trees reach 50-90 feet tall and about half as wide in the wild, though just 20-30 feet tall in gardens. Needles are light blue-green. These plants are great for rock gardens, containers, and as bonsai subjects as well. Variety 'Elizabeth' grows to 1 foot tall and 3 feet wide with blue-green soft foliage. |
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Tsuga sieboldii (Southern Japanese Hemlock, Tsuga) These trees, sometimes used as ornamentals in larger landscapes, are native to Japan. The species forms a multi-stemmed base and a dense, broadly conical crown. Bark is dark greyish pink in color, and foliage is green. These trees can reach up to 100 feet tall, but are more commonly seen at about half that size in garden cultivation. |
Caring for and pruning Tsuga Trees
Plant Hemlock trees in early springtime in a spot in the garden that receives full to partial shade. They can tolerate full sun in cold northern climates, but otherwise appreciate a good amount of sun protection. They should be planted about 30 to 40 feet apart. Hemlocks are shallow-rooted, and will need some protection from strong winds to keep from falling over. Ensure that soil is well-draining; if local soils do not drain well, amend the planting site with plenty of organic material and/or sand before installing trees. Soil should ideally have a pH of between 5.0 and 6.8. Apply a thick layer of mulch around the base of trees to suppress weed growth, increase soil moisture retention, and help to regulate soil temperatures. Water newly planted trees regularly, ensuring that good drainage is occurring. Mature trees also appreciate moist soil, and should be deep watered weekly for best performance and growth.
Unless damaged by weather or disease, these trees really don't need much pruning. They take a handsome pyramid to conical shape and are best pruned in spring or early summertime. Compact cultivars are commonly used as foundation hedge plants or for privacy, and can be trimmed to maintain their shape, as long as prunings begin when trees are young. Mature trees should not have too much of their shape or foliage changed; they will not react well.
Unless damaged by weather or disease, these trees really don't need much pruning. They take a handsome pyramid to conical shape and are best pruned in spring or early summertime. Compact cultivars are commonly used as foundation hedge plants or for privacy, and can be trimmed to maintain their shape, as long as prunings begin when trees are young. Mature trees should not have too much of their shape or foliage changed; they will not react well.
Propagation
Tsuga can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Tsuga tree, follow the instructions below:
Propagating Tsuga by Cutting
Propagating Tsuga by Seed
Propagating Tsuga by Cutting
- Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand.
- In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
- Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
- Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.
Propagating Tsuga by Seed
- Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
- Harvest your seeds. They are contained inside of the female cones produced by trees in late August and early September. Each mature cone contains between 30 and 40 seeds, depending on the species, size of the cone, and maturity of the tree that produces them.
- Place harvested seeds in a sealable bag or container filled with moistened peat moss or sand, and place the container in the refrigerator for between three and four months' time. This cold-stratification period is typically necessary for seeds to germinate. After this time has passed, bring seeds out and sow them.
- Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 7-14 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
- Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.
Tsuga seeds are contained inside of the female cones produced by trees.
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Tsuga seeds.
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Problems and Pests
Tsuga plants are susceptible to the following landscape pests and diseases:
- Hemlock Wooly Aphids
- Tip Blight
- Phomopsis Twig Blight
- Needle Rust
- Basal Canker
- Cytospora Canker
- Fabrella Needle Blight
- Cone and Twig Rust
- Sun Scorch
- Hemlock Rust Mite
- Bagworms
- Gypsy Moths
- Spruce Leaf Miner
- Grape Scale
- Spruce Budworm
Gallery
A pair of young Tsuga trees.
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Tsuga heterophylla 'Thorsen's Weeping'.
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These trees provide beautiful evergreen foliage.
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Use dwarf cultivars in mixed beds and borders for evergreen color.
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Many cultivars of Tsuga species have beautiful foliage that droops towards branch tips.
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These trees have evergreen, needle-like foliage.
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Videos
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Learn how to identify Mountain Hemlock plants.
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Learn about the history of these trees.
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Resources
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Pages 639 - 640, Tsuga
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