Arborvitae is a genus of evergreen trees belonging to the cypress family. The word derives from Latin "arbor vitae" meaning tree of life, and was coined by John Claudius Loudon in 1838.
Arborvitae are used as ornamental plants in gardens and parks around the world because they make excellent hedges, screens, topiary subjects for formal gardens or informal plantings under power lines. They can also be found planted along many streets throughout North America.
Arborvitae prefer moist soil with good drainage; they will not thrive if water stands on their roots for more than about an hour at a time. It's important to note that large arborvitae have extensive root systems and invasive roots are not to be taken lightly.
The Japanese Arborvitae is the most commonly grown and widely distributed of all Arborvitaes. It has a pyramidal shape when young eventually growing to a free-shaped, broad topped tree in maturity.
Japanese arborvitae are generally uniform in color light green to gray green. They grow best in full sun to partial shade and are hardy to 0 degrees F (-18 C).
Japanese arborvitae can reach heights of 80 to 100 feet (24 m) with a spread of 10 - 25 feet (3 - 7.6 m). They are slow growing and dense, so they will need to be pruned at least yearly. The foliage has a pleasant cedar-like fragrance when crushed or rubbed.
No one cultivar of Japanese arborvitae is superior to another. The four most commonly planted are 'Green Dragon', 'Pyramidalis', 'Sky Pencil' and "Columnaris." Although some nurseries report that Columnaris is the best, this cultivar has been known to develop stem suckers (suckers are the shoots that grow from dormant buds below the soil line) in some locations.
Japanese Arborvitae responds well to shearing, if not left unpruned a single tree will form a ball-like top with no branches. Shear when the plants are dormant (usually in late winter), but before new growth starts. If you prefer a bushy top and sides, shear after new growth starts the following spring.
The Leyland Cypress is an arborvitae that is commonly used as a garden ornamental, it's also the most frequently planted living Christmas tree species.
It has a narrow form with a flat topped crown and grows very well in a range of conditions. The foliage is a bluish-green color, similar to the Blue Atlas Cedar, but much more dense.
Leyland Cypress prefer full sun or light shade and are short lived as ornamentals, growing only 10 - 25 feet (3 - 7.6 m) tall. They also have a tendency to develop leylandii dieback, when grown in the shade as they age.
The Leyland Cypress is not resistant to arborvitae scale, but like the Japanese Arborvitae it is usually not bothered by deer unless their numbers are excessive .
This is a very popular arborvitae, both in the UK and North America because of its fast growth rate. European Arborvitae can reach 40 feet (12 m) tall with a 15 foot (4.5 m) spread within 10 years if left unmanaged.
It has a rounded to oval crown that is dense and compact. It also has the narrowest leaves of any arborvitae, 1/2" (1.27 cm) wide with serrated margins. The European Arborvitae prefers full sun or partial shade.
It is one of the most cold tolerant arborvitae growing in hardiness zones 4 - 8. However, it has a tendency to become leggy and not develop a full crown if grown in shade. Also, as with the Leyland Cypress, European Arborvitae can also develop leylandii dieback as it matures.
If you are planning to use this cultivar as a privacy screen, plant it at least 10 feet (3 m) from your house and don't plant it near any structure where leylandii dieback is likely to fall on someone.
European Arborvitae can be sheared to help form a full, rounded crown. If you desire an open and airy appearance shear it to the ground after it is filled out in about five years. If left unpruned it will become leggy and lose its lower branches to sun scalding.
The Chinese Arborvitae is a slow growing, single stemmed tree that can reach about 60 feet (18 m) tall and 15 - 20 feet (4.5 - 6 m) wide with an open crown. It has the largest leaves of any arborvitae species, up to 5" (12.7 cm) long and 2" (5.1 cm) wide with serrated edges.
The foliage is a very dark green color, almost black when young. It prefers to be planted in full sun or partial shade.
Chinese Arborvitae can develop some stem suckers as it ages, but not nearly as much as the Japanese Arborvitae. It is only moderately tolerant of urban pollution and will not grow well in the smoggy cities along the east coast.
When grown under ideal conditions it can live to be 80 - 100 years old, but is often short lived in our cities where air quality is poor.
Interestingly, this cultivar is resistant to arborvitae beetle infestation and will not be bothered by deer unless their numbers are excessive.
The American Arborvitae is very similar to the Leyland Cypress in appearance, with a flat topped, narrow crown. It has slightly narrower leaves than the European or Leyland White Arborvitae and will grow up to 36 feet (11 m) tall.
American Arborvitae is considered one of the most beautiful of all true arborvitae.
It prefers full sun, but will tolerate partial shade. It is hardy in zones 4 - 8 and grows well in moist soils with good drainage. This cultivar has a tendency to develop scale insect problems more readily than the Japanese Arborvitae, as well as being susceptible to spider mites .
American Arborvitae should not be grown near a structure where it has the potential to cause structural damage. It can become quite large with an open crown and could potentially cause some roof problems if allowed to grow into the thatch, which becomes flammable.
Emerald Green Arborvitae
This is an interesting cultivar that has the widest leaves of any arborvitae (up to 5"/12.7 cm wide) and grows in an uneven, twisted fashion with a flat top. The twisted growth habit will cause it to have a bushier appearance overall than other arborvitae cultivars.
The Emerald Green Arborvitae has good tolerance of both urban environments and salt spray. It will gradually loose its lower branches to sun scalding as it ages, but overall it is a fairly slow growing cultivar for an arborvitae.
Emerald Green Arborvitae grows best in full sun or partial shade, with a slight edge to full sun. It can also develop scale insect and spider mite problems in some climates, particularly areas of high humidity and mild winters.
The cultivar name for the Emerald Green Arborvitae is 'Smaragd'.
Virginia Creeper Arborvitae
The Virginia Creeper Arborvitae is a suckering cultivar which also has the tendency to produce many stem sprouts. It can be grown as a multi-stemmed tree or pruned to form an irregularly shaped bush, similar to the Emerald Green Arborvitae.
Virginia Creeper Arborvitae will grow up to 20 feet (6 m) tall and 10 - 15 feet (3 - 4.5 m) wide with a rounded crown when mature. It is very similar in appearance to the Emerald Green Arborvitae, except it has green leaves instead of dark green.
Virginia Creeper Arborvitae will tolerate full sun or partial shade, but prefers full sun. The cultivar name for this species is 'Virginica'.
Leyland Cypress Arborvitae
The Leyland Cypress is a large, leggy tree with an upright habit and wide open crown when mature. It has a blue-gray color to its foliage which gives it the appearance of cypress foliage, hence the name.
The Leyland Cypress prefers full sun or partial shade. It grows in a more upright fashion than the other arborvitae cultivars and will make a good choice for the "tree line" zone where trees are grown up to the property line .
The Leyland Cypress has good tolerance of both urban environments and salt spray. It is also resistant to arborvitae beetle infestation .
The Leyland Cypress has the tendency to develop scale insect problems in areas of high humidity. It can also develop bacterial leaf scorch (Xylella fastidiosa), which is a disease that causes death of the foliage and requires immediate removal of infected plant material and replacement with resistant cultivars. The cultivar name for the Leyland Cypress is 'Carolina Sapphire'.
Thuja orientalis (Turkish arborvitae or Oriental arborvitae)
The Turkish arborvitae is the most cold hardy of all true arborvitae. It will tolerate temperatures as low as -50 degrees F (-45 C).
Turkish (Oriental) Arborvitae grows in a pyramidal, conical shape and can grow to be very large when allowed to grow unhindered. It has a narrow crown in comparison to other arborvitae cultivars which allows it to be planted closer together than other species, thus reducing overall maintenance costs for larger plantings.
This cultivar also has the widest range of soil tolerance of any true arborvitae. It will grow in a wide range of soils from heavy clay to very stony, and is also salt tolerant. Turkish (Oriental) arborvitae will tolerate full sun or partial shade, although it prefers morning sun and afternoon shade.
The cultivar name for the Turkish (Oriental) arborvitae is 'Aurea Nana'.
The Western Red Cedar (Thuja plicata) is also known as the American Arborvitae. It has grayish green foliage, and is sometimes considered to be an upright cultivar of the Thuja Occidentalis species.
This cultivar will grow in a pyramidal shape when young, however it tends to grow taller and wider in an irregular, wide-spreading fashion as it matures. It will reach heights of 40 feet (12 m) tall and 10 - 20 feet (3 - 6 m) wide when mature.
Western Red Cedar prefers full sun or partial shade, but can tolerate some shade if required. It also prefers dry, well-drained soil, and will grow in a wide range of soils.
Western Red Cedar is resistant to the arborvitae beetle (Thanasimus formicarius), although it can still develop scars from the feeding of other insects such as aphids and mealybugs which are attracted to its foliage. The cultivar name for the Western Red Cedar is 'Tidewater'.
Thuja standishii (Standish Arborvitae)
The Standish Arborvitae is a cultivar of the Western Red Cedar (Thuja plicata). It has bronze colored foliage and grows in a pyramidal shape.
Standish Arborvitae is a more compact plant than its parent species, growing only 25 feet (8 m) tall with a 6 - 10 foot (2 - 3 m) spread. It also has a narrower crown than the Western Red Cedar, making it suitable for closer spacing in landscaping .
Q: What do Arborvitae trees need most to grow?
A: Arborvitae trees seem to thrive in moist soil, but as long as the soil doesn't dry out, they can be watered less frequently. Arborvitae trees do need a good bit of sun. They develop the classic odd-shaped look when they get too little light.
Light can be added to places where they grow poorly by pruning the top 15 or so inches of a tree near its base. The tree will branch out again and increase its opportunities to collect light.
Q: What's the best way to prune these trees?
A: Allow them to grow as they will and don't do any major cutting until they stop growing or start getting too tall. Then cut off old branches at an angle about 8 to 12 inches above where you want new ones to start.
The amount of time it takes for new growth to appear will vary among different species. But you can tell if the branches are still alive because they won't feel brittle and will have "green bark" at their base. If you're unsure, cut back a little farther from where you want new branches to grow.
Q: How tall can they get?
A: The giant arborvitaes, which are also called False Cypress , can get to heights over 100 feet. Other species may approach 50 feet but will begin to have health problems at that height.
Some people trim the tops of their ornamental trees down to 1 foot and then, if desired, prune lower branches for a shorter shape or take the trees out of pots and plant them in the ground.
Q: Do they need much maintenance?
A: Other than a little pruning, these trees don't require much upkeep. They are also slow growing and low-maintenance. It's fine to put one of their cuttings directly into the soil outside, where it will take root and develop into a new tree on its own.
Q: Do they need much water?
A: Like all evergreens, arborvitaes do better in a well-drained soil that doesn't stay too wet but also doesn't dry out. They can grow in sandy loam as long as it's not too heavy.
Q: How do I know if they're getting enough water?
A: When the leaves are droopy and begin turning brown at their edges, it means that the tree is overly dry. If only a couple of branches are affected, you can lift them slightly to allow more moisture to reach them. In general, don't water a tree when the soil is dry.
Q: Are they susceptible to any diseases or pests?
A: Japanese beetles are attracted to them, and if you don't want to use chemicals for control, try hanging some yellow sticky traps from the branches of your ornamental trees. You can also spray Bt ( Bacillus thuringiensis ) on the leaves. It's a specific natural bacteria that kills only the beetles and won't harm other insects or people.
There are also several insecticides containing imidacloprid for control of Japanese beetle larvae. This is a relatively new product that works on grubs (Japanese beetle larvae), but does not cause damage to honey bees.
Are arborvitae trees evergreen year-round?
For the most part, yes - however there is one cultivar of true Arborvitae tree that is deciduous. This cultivar is also known as American Arborvitae, and is called Thuja occidentalis 'Aurea Nana'.
It has a conical shape, and will drop most of its needles each fall - leaving prunus-like buds on the branch tips. These buds will lengthen and grow into new needles in the spring.
Do arborvitae trees grow well in containers?
Arborvitae trees are one of the plants that do quite well in containers, at least as long as you have a good growing medium. They really don't need to be repotted very often - perhaps every 3-5 years is all the work they require keeping them in a container.
However, as they grow larger in containers, you will need to have a plan for moving the container (or the tree). You can place it on a trailer or dolly so that when it gets too big to move easily, you only have to lift it up and put it down again - but whatever method you use needs to ensure that the base of the tree comes into contact with fresh soil each time you re-plant it. When this is done properly, they can be very long lived in containers - perhaps as long as 25 years!
Arborvitae trees are a popular plant to grow in gardens, as they are very versatile and come in many sizes, shapes and colors. They are also quite easy to maintain.
You can use them for specimen trees, or to add an accent of color where that is needed in your landscape (for example along the edge of a pond, or along the side of a house).
And don't forget to check out our other informative articles about many types of plants that can be found around your property. You may also be interested in finding resources on gardening for kids .