thuja
( THOO - juh )
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At-A-Glance InformationThis genus of evergreen trees and shrubs known commonly as Arborvitae need partial shade in warmer climates and moderate to regular water. Members of the genus are commonly known as Arborvitaes, Thujas, or Cedars. They are neat, symmetrical plants that are great when formed into globes, cones, and cylinders. New foliage is feathery. They produce small cones that are green to blue-green and turn to brown with age. They can handle both damp and dry soils, but do best in well-draining soils.
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thuja Species and Varietals
The coniferous genus Thuja includes five species, and is a member of the plant family Cupressaceae. Two species are native to North America and three species are native to eastern Asia. Growing zones vary depending on the species. For more information, see the descriptions below. To find your zone, click here: Zone Map.
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Thuja koraiensis (Korean Arborvitae) Native to Korea and extreme northeastern areas of China, this species is rarely seen, and is considered to be vulnerable to extinction. It forms an evergreen shrub to between 10 and 33 feet tall when mature. Foliage is green with bright white undersides. Occasionally grown as an ornamental. |
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Thuja occidentalis (American Arborvitae, Northern White-Cedar, Eastern White-Cedar, Swamp Cedar, Eastern Arborvitae)
This species grows in zones A2, A3, 1-9, 15-17, 21-24, H1 and H2 and is native to the eastern United States. It has an upright, open habit reaching 30-60 feet tall and 10-15 feet wide. Leaf sprays are bright green to chartreuse, and turn brown and scorched in cool temperatures. Needs moisture in the air to perform at its best. This species is sensitive to spider mites infestations. Choice selections are listed and described below.
This species grows in zones A2, A3, 1-9, 15-17, 21-24, H1 and H2 and is native to the eastern United States. It has an upright, open habit reaching 30-60 feet tall and 10-15 feet wide. Leaf sprays are bright green to chartreuse, and turn brown and scorched in cool temperatures. Needs moisture in the air to perform at its best. This species is sensitive to spider mites infestations. Choice selections are listed and described below.
'Brandon'
12-15 feet tall and 6-8 feet wide. Great as a screen. |
'Degroot's Spire'
Narrow, green column 10-20 feet tall and 4-5 feet wide, great as a narrow screening plant. |
'Douglasii Pyramidalis'
Fast-grower to 15 feet tall and 10 feet wide. |
'Fastigiata'
('Pyramidalis', 'Columnaris') This variety has a dense, columnar growth to 25 feet tall and 5 feet wide, and it tends to get a bit unruly with spreading branches; set 4 feet apart for a screen. |
'Golden Globe'
Dense, rounded plant to 3-5 feet tall and wide, with bright golden foliage. |
'Hetz Midget'
Globe shaped with rich green foliage, to 3-4 feet tall and wide. |
'Lutea' ('George Peabody')
Narrow, conical tree to 30-35 feet tall and 10-15 feet wide, with soft yellow new growth that ages to gold. |
'Nigra'
Dark green foliage on a dense growing cone to 20-30 feet tall and 4-5 feet wide. |
'Rheingold'
('Improved Ellwangeriana Aurea') This variety is cone-shaped to 6 feet tall and wide, with a mixture of scale and needle foliage in bright gold. |
'Smaragd' ('Emerald', 'Emerald Green')
This is a neat, dense growing conical variety with green foliage to 10-15 feet tall and 3-4 feet wide. |
'Spiralis'
Fast-growing tree to 30-45 feet tall and 10-15 feet wide, with dark green foliage that gives it a ferny look. |
'Sunkist'
Slow-grower to 4-6 feet tall and 2-3 feet wide with bright gold foliage. Great for bonsai. |
'Woodwardii'
Commonly grown globe-shaped shrub to 4 feet tall and wide in about 10 years. |
'Yellow Ribbon'
8-10 feet tall and 2-3 feet wide, with bright yellow foliage that holds year-round. |
Thuja plicata (Western Red Cedar, Pacific Red Cedar, Giant Arborvitae, Western Arborvitae, Shinglewood)
This species is native to Northern California, up to Alaska and east to Montana. Plants are hardy, and can reach over 200 feet tall in their natural habitat. Grown in gardens, they top out more around 50-100 feet tall and 25-60 feet wide. Drooping branchlets are dark green and lower branches spread broadly. Varieties of this species are listed below.
This species is native to Northern California, up to Alaska and east to Montana. Plants are hardy, and can reach over 200 feet tall in their natural habitat. Grown in gardens, they top out more around 50-100 feet tall and 25-60 feet wide. Drooping branchlets are dark green and lower branches spread broadly. Varieties of this species are listed below.
'Collyer's Gold'
Slow grower, upright habit to 4-6 feet tall and about half as wide, with dense foliage emerging yellow and maturing to a bright green. |
'Green Giant'
Grows 3-5 feet per year, eventually reaching 30-50 feet tall and 10-20 feet wide; used as a tall hedge or screen. |
'Spring Grove'
8-10 feet tall in 5 years, and at maturity reaches 40-60 feet tall and 10-15 feet wide. Can be used as a sheared hedge. |
'Stoneham Gold'
Dense, sow growing dwarf variety that reaches 6 feet tall and 2 feet wide, with orange-yellow new growth. |
'Sunshine'
Foliage is bright gold, reaching 15-30 feet tall and 10-15 feet wide, with best color in full sun exposure. |
'Whipcord'
Dwarf variety with threadlike foliage and cascading bright green branches. To 5 feet tall and 4 feet wide, with bronze winter foliage. |
'Zebrina'
Slow grower, with foliage banded in green and yellow. To 50-100 feet tall and 25-60 feet wide. |
Caring for and pruning thuja shrubs
Plant these shrubs in full to partial sunlight; they should be receiving at least 6 hours of direct sun each day for best performance. Arborvitae can tolerate a wide variety of soils, but prefer them to have a pH between 6.0 and 8.0. Amend soil with plenty of organic matter before planting, and mulch around the base of the plant afterwards to increase soil moisture retention. Thuja requires regular waterings, especially during periods of drought and warm weather. Allow the soil to dry out slightly between waterings; newly planted Arborvitae shrubs will need more regular waterings than established ones.
These shrubs and trees respond well to pruning and shearing, and are commonly used as subjects for topiary. Regular pruning can be completed annually in late winter or early spring to remove dead or diseased growth and maintain shape and size. Arborvitae do not need heavy feedings, though applying a slow-release, balanced fertilizer in springtime can help to promote healthy growth for the season. Avoid fertilizers that are nitrogen-rich, as it can lead to dense, weak growth in these plants. Winter damage can sometimes occur in these plants, especially in areas with prolonged periods of frost. Protect young plants with burlap wrap to avoid losing them over the cooler months of the year.
These shrubs and trees respond well to pruning and shearing, and are commonly used as subjects for topiary. Regular pruning can be completed annually in late winter or early spring to remove dead or diseased growth and maintain shape and size. Arborvitae do not need heavy feedings, though applying a slow-release, balanced fertilizer in springtime can help to promote healthy growth for the season. Avoid fertilizers that are nitrogen-rich, as it can lead to dense, weak growth in these plants. Winter damage can sometimes occur in these plants, especially in areas with prolonged periods of frost. Protect young plants with burlap wrap to avoid losing them over the cooler months of the year.
Propagation
Thuja shrubs are best propagated either by using cuttings. To propagate your plant, follow the instructions below:
Propagating Thuja by Cutting
Propagating Thuja 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 late summer or early fall, 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 5 to 9 inch portion(s) of the end of a healthy branch. Ensure that the cutting has both hard and soft wood, and that the foliage is healthy. 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 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.
Problems and Pests
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Arborvitae shrubs and trees have issues with the following pests and diseases:
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For information on these pests and diseases, including treatment techniques, see the following links:
Gallery
These shrubs are perfect for topiary gardens.
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Use Thuja as architectural accents in mixed beds.
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Differently colored species can add pops of color to planting beds.
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Videos
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How large can a Green Giant really get?
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All you need to know about this genus of trees.
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This colorful varietal can add pizzazz to evergreen gardens.
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Learn about Tom Thumb Arborvitae.
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Growing tips for Green Giant Thuja.
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How to propagate Thuja shrubs and trees.
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Resources
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Pages 627 - 628, Thuja (Arborvitae)
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