The arborvitae genus of shrubs and trees includes three different species, comprising a large number of evergreens. Their popularity is largely due to their fast-growing, 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. This cultivar is sometimes also known as 'Smaragd,' because the plant was originally developed in Denmark (Smaragd is the Danish word for emerald).
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 fall. Most specimens grow to be seven to 15 feet in height, but can occasionally reach upwards of 20 feet. It also makes a good foundation plant and is sometimes planted singly as a landscape specimen plant. Occasionally, this plant is pruned to form spiral topiaries.
|Botanical Name||Thuja occidentalis|
|Common Names||Emerald green arborvitae, Smaragd arborvitae, American arborvitae|
|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 Areas||North America|
|Toxicity||Mildly toxic to animals|
Watch Now: How to Grow and Care for a Emerald Green Arborvitae
Emerald Green Arborvitae Care
In order 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). Since these are fast-growing plants, leave three to four feet between each if you are planting as a hedge 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 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.
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.
Your arborvitae will need watering twice weekly for the first few months after planting, then weekly watering (about one inch) for the next year or so. Once established, make sure it gets about a half-inch of water weekly, either through rainfall or irrigation. Too little water will cause the foliage to turn yellow or brown, while excessive water may cause needle discoloration and root rot.
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 three to four feet apart from one another in order to improve air circulation. Avoid exposed, windy locations, especially in colder climates.
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.
Is Emerald Green Arborvitae Toxic?
Emerald green arborvitae is considered toxic to animals, though only mildly so unless massive amounts are ingested. The issue lies in the plant's essential oils, which contain the neurotoxin known as Thujone, the largest concentration of which can be found in the cones, wood, and at the end of the twigs. If you notice your animal exhibiting any of the below issues, contact an emergency vet immediately.
Symptoms of Poisoning
- Skin irritation
- Irritation around or inside the mouth
Pruning Emerald Green Arborvitae
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 Diseases
Arborvitaes are rarely troubled by insect and disease problems, but they sometimes suffer 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. Bagworms may also feed on the foliage of arborvitaes. Control them by handpicking the egg bags and destroying them before the insects hatch. Spider mites and stem canker can also be problems.