Thuja Occidentalis Guide: How to Grow & Care for “Northern White Cedar”

When it comes to low maintenance ornamental trees, Thuja Occidentalis is one of the most popular choices for gardeners of all skill levels. Also known as Eastern Arborvitae (tree of life), Northern white cedar, or swamp cedar, this evergreen coniferous tree is very popular in eastern Canada and the north-central United States.

Thuja belongs to the Cupressaceae family, being related to junipers and redwoods. The species in this family are important timber sources, but the Northern cedar is a small or a medium-sized tree at most, so it is not used heavily for timber. Nonetheless, as you are about to discover its ornamental qualities and a few other hidden benefits make it more valuable than a mere timber source.

Read on to learn more about Thuja – a very popular ornamental shrub.

About Thuja Occidentalis

• The name Arborvitae comes from Latin and it means “tree of life”. The northern cedar got this name due to the fact that, in many cultures, it was believed to have valuable medicinal benefits.
• This coniferous tree is native to eastern Canada, but it has become very popular across the world as an ornamental garden tree.
• In Canada, its range reaches the arctic treeline, but Thuja shrubs can be naturalized in most locations with cool summers.
• Thuja prefers wet forests and coniferous swamps. While it is not listed as an endangered species, its population is often threatened by deers that feed on its bark.
• The Northern cedar’s bark, twigs, leaves, and even young branches are all used for various medicinal properties. The leaves, the bark, and the branches are used to produce a colorless oil with a scent similar to camphor. The oil has numerous benefits, but it needs to be used with caution, as it contains thujone, a powerful poisonous chemical.
• A decoction made from leaves and twigs was used to treat cough, fever, and even venereal diseases. Nowadays this tree is still being used to treat warts, polyps, bronchitis, and other respiratory diseases.
• Thuja also has antibacterial and antifungal properties, and recent studies have shown that it can stimulate the immune system. Given its many medicinal uses, it is no wonder that this evergreen has been known for centuries as the tree of life.
• Thuja Occidentalis is sacred to the Ojibwe people, which are among the most numerous indigenous peoples found north of Rio Grande. The Ojibwe call it the Grandmother Cedar and they have listed it as one of the four major plants of their medicinal wheel.
• No remedies made of Arborvitae are recommended to pregnant women as it can cause complications or even miscarriages.
• Arborvitae plants can be toxic to most pets, especially cats, dogs, and horses. Ingestion of various tree parts can cause allergic skin reactions, swelling, breathing problems, and stomach problems.

Thuja Occidentalis Features: An Overview

• This evergreen tree can grow up to 20 meters in height. It features a conical crown with a narrow, rounded top. The largest known specimen is 34 meters tall and it has a diameter of 175 centimeters.
• It usually has a single trunk that can reach a diameter of up to one meter and it has a  red-brown bark that peels in vertical strips. Mature trees can sometimes have a gray bark.
• Its straight branches have a fan-like distribution and they are covered in scaly leaves.
• The Eastern arborvitae grows male blooms which produce female cones. The cones are rather small, they have an elongated shape and overlapping scales. The seed cones have a yellow-green color and they each contain about 8 seeds.
• There are over 300 cultivars featuring variations in shape, size, and color.
• Thuja is a very sturdy tree and it easily catches roots. It is very common for the branches of a fallen tree to catch roots, even in the most unlikely locations.
• It is known to live a very long life. The longest live specimen is over 1100 years old, but a dead specimen with over 1600 rings has also been recorded.
• Commercially, the northern white cedar is used for rustic fences, log cabins, and canoes. Its oil is commonly used for cleaners and disinfectants.
• While Thuja is a very resilient shrub, it can sometimes be affected by conifer aphids and scale insects.

Growing Thuja Occidentalis

As we already mentioned, if you plan on growing this ornamental tree in your garden, you can easily do so if you live in an area with cool summers, where July temperatures don’t exceed 20 °C. This ornamental tree is hardy to USDA zone 3. If you plan on growing several trees in your garden to create a natural screen or a fence, make sure to leave sufficient space between the trees. Normal-sized varieties should have about 4 meters between them, whereas dwarf varieties should have about 50 centimeters between them.

Thuja shrubs prefer full sunlight or partial shade. They thrive in well-drained soils, but they can also survive in swamps. The amazing adaptability and small size help these shrubs to outcompete other trees with ease. They prefer neutral to alkaline soils.

Since Thuja is a very slow-growing tree, it will need some fertilization for a growth boost. It is best to use a balanced liquid fertilizer at the beginning of each growing season.

This tree is very resilient to harsh weather. Nonetheless, young plants are more sensitive so it is best to protect them from high winds in the early years. Also, if you notice snow or ice build-up at the base of the tree or on the branches, it is best to remove it, to prevent damage. You can cover the tree with a mesh during heavy snowfalls, so you don’t have to tend to its needs during the wintertime.

This lovely ornamental tree will not require any pruning, since it has a natural columnar shape. Nonetheless, if you grow it as a hedge, you can prune it as often as you need. The northern white cedar is resilient and pruning won’t affect its well-being in any way.

Watering Thuja Occidentalis

A mature Thuja tree will be perfectly capable of gathering moisture from its environment, provided that you don’t live in a very dry area. Nonetheless, it might need occasional watering, especially during the hotter seasons. This tree likes its soil moist but well-drained. If you feel that your garden soil does not drain properly, add some grit to a depth of 20 cm.

Young trees will need to be watered more frequently. At least in the first growing season, you should water the arborvitae daily, for about 10 minutes. As the tree matures, the watering frequency will decrease and it will depend heavily on the weather and the soil. The best thing you can do is check the soil regularly, and make sure it is always moist. Mulch and other organic material will help the soil retain moisture for longer periods.

Propagating Thuja Occidentalis

The Northern White Cedar can easily be propagated through semi-hardwood cuttings. The ideal propagation period is in late summer, but early autumn also works well.

This evergreen tree can also be grown from seed, but keep in mind that it is a rather slow-grower so you must have a lot of patience with it. To grow from seed, place 5-6 cones in a paper bag and put the bag in a sunny location so that the cones can dry. Once the cones are fully dry, shake the bag to remove the seeds.

Plant the seeds on a seed moss tray and cover it with a glass lid. Place the tray in a sunny location. Ideally, you should do this procedure in the spring and you should allow the seedlings to grow to about 7 cm tall before transferring them to a more permanent location.

When planting the seedlings, make sure that the holes you dig are only slightly bigger than the seedling root balls. Place a thin layer of potting compost in the holes, plant the seedlings, and then cover them with soil. Compress the soil around the seedlings to give them good support and water them regularly until they reach maturity.

In conclusion

If you live in a northern location, you are probably very familiar with this tree. It is very common in parks and other public places, but also in private gardens where it is used for screens and hedges.  Since it is a slow-growing tree, it will take a long time to reach its full size, and even then it won’t take a lot of space, so this tree is even suitable for small gardens.

Its resilience makes it suitable even for beginner gardeners. If your local environment is similar to its natural habitat, this tree will require very little maintenance. It doesn’t need any pruning, and as long as you keep its soil moist, it will reward you with luscious green foliage all year long. However, if you want to get creative with its shape, you can prune your Thuja as often as you want, without fear of damaging it or hindering its growth.

Now you know the basics of growing and caring for Thuja shrubs. Ready to add some to your beautiful garden? Let us know in the comments!