How to Grow and Care for Emerald Green Arborvitae Trees

Emerald green arborvitae trees alongside brick pathway and white and blue building

The Spruce / Evgeniya Vlasova

The popularity of evergreens is largely due to their easy-to-care-for nature and the year-round visual interest they can bring to a landscape. One of the more popular cultivars of the arborvitae species is known as 'Emerald Green', which is highly prized as a hedge or screen plant, especially in colder climates.

Emerald green arborvitae is best planted in the fall when it will experience minimal heat stress. Its foliage consists of flat sprays of glossy bright green needles, plus urn-shaped cones about an inch long that turn reddish-brown in the fall. Most specimens grow at a fast rate early on and slow down as the tree matures, reaching 7 to 15 feet high, and possibly reaching 20 feet. Occasionally, this plant is pruned to form spiral topiaries. The tree is toxic to humans and animals.

Common Name Emerald green arborvitae, Smaragd arborvitae, American arborvitae
Botanical Name Thuja occidentalis
Family Cupressaceae
Plant Type Needled evergreen
Mature Size 12–20 ft. tall, 3–10 ft. wide
Sun Exposure Full sun, partial shade
Soil Type Moist but well-drained
Soil pH Acidic, alkaline
Bloom Time Does not bloom
Flower Color Does not bloom
Hardiness Zones 2–7 (USDA)
Native Area North America
Toxicity Toxic to people, toxic to cats, dogs, and pets
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Emerald Green Arborvitae Care

This cultivar, sometimes also known as 'Smaragd', because the plant was originally developed in Denmark (Smaragd is the Danish word for emerald), also makes a good foundation plant and is sometimes planted singly as a landscape specimen plant.

For the most successful tree, plant emerald green arborvitae in moderately moist, well-drained soil in full sun or partial shade (in warmer climates, some shade is preferable). Leave 3 to 4 feet between each tree if you are planting as a privacy fence or screen. Heavy snow can break branches, so brush them off after a storm—broken limbs should be pruned off, and the plants may need to be staked upright until they recover.

Emerald green arborvitae tree leaves closeup

The Spruce / Evgeniya Vlasova

Emerald green arborvitae tree branches in sunlight

The Spruce / Evgeniya Vlasova

Emerald green arborvitae tree tops against blue sky

The Spruce / Evgeniya Vlasova

Emerald green arborvitae tree branches with pine cones on branches

The Spruce / Evgeniya Vlasova

Emerald green arborvitae tree branch and glossy leaves closeup

The Spruce / Evgeniya Vlasova

Light

Emerald green arborvitae should be grown in full sun or partial shade. They generally need at least six hours of sun daily, but too much direct sunlight can stress the plant and burn the foliage. However, they should not be planted in full shade either, since this can greatly reduce the density of the foliage.

Soil

Plant arborvitae in moist but well-drained soil that boasts a neutral to alkaline pH level. These shrubs do not like to have their roots in soggy soil, so apply a heavy layer of compost or mulch over the root zone each year to preserve soil moisture.

Water

Your arborvitae will need watering twice weekly for the first few months after planting, then weekly watering (about 1 inch of water) for the next year or so. Once established, make sure it gets about a half-inch of water weekly, either through rainfall or irrigation.

Temperature and Humidity

Emerald green arborvitae does better in cooler, dryer climates. In very humid conditions, fungal diseases can be a problem. To help prevent this, plant your trees at least 3 to 4 feet apart from one another in order to improve air circulation. Avoid exposed, windy locations, especially in colder climates.

Fertilizer

Arborvitae plants normally do not need feeding. However, if new growth is very sparse or slow, an application of a balanced fertilizer containing all major nutrients is recommended.

Pruning Emerald Green Arborvitae

If desired, light pruning in the early spring can help your arborvitae remain neat and foster thicker growth. To do so, trim the leafy parts of the branch, making sure not to cut back to bare wood. Dead or diseased branches should be removed to prevent decay and improve air circulation.

In addition, you may prune your tree to maintain the natural shape of the shrub, which is wider at the bottom and tapering inward toward the top. Especially adventurous gardeners can even prune the shape to form spiral topiaries.

Common Pests and Plant Diseases

Arborvitaes are rarely troubled by insect and disease problems. Bagworms may feed on the foliage of arborvitaes. Control them by handpicking the egg bags and destroying them before the insects hatch. Spider mites can also do damage to the trees.

The plant can sometimes suffer from needle and twig blight caused by fungi, especially if air circulation is poor. To control blight, prune off all affected branches and treat them with a fungicide.

Keep an eye out for stem canker, a fairly serious fungal disease that causes lesions, sores, and sticky oozing resin from the trunk or branches. Remove the affected branches. If the trunk is affected, the tree may not survive.

FAQ
  • Are emerald green arborvitae easy to care for?

    They are extremely easy to care for and need little to zero maintenance.

  • How fast does emerald green arborvitae grow?

    These slim trees grow at a faster rate of speed when they are young, adding 1 to 2 feet per year. As the tree matures, the growth rate will slow down to about 6 inches a year until reaching full height.

  • How long can emerald green arborvitae live?

    The lifespan of emerald green arborvitae varies, from 25 years up to 150 years.

Article Sources
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  1. University of California Agriculture, and Natural Resources. “Toxic Plants (by Common Name).” Ucanr.edu. N.p., n.d. Web.

  2. Plants Toxic to Dogs List, Symptoms and Treatment.” Dog-health-guide.org. N.p., 2 Dec. 2020. Web. 

  3. Elisabeth C. Miller Library: Gardening Answers Search Results for ‘Plant Longevity.’” Washington.edu. N.p., n.d. Web.