Emerald Green Arborvitae (Thuja occidentalis ‘Smaragd’) is a compact, evergreen conifer that belongs to the Cupressaceae family. It is a cultivar of Thuja occidentalis, commonly known as Eastern Arborvitae or Northern White Cedar, which is native to eastern North America. The cultivar name ‘Smaragd’ is derived from the Danish word for “emerald,” referencing the tree’s vivid green foliage. This cultivar is prized for its elegant, narrow, and formal appearance, making it a favorite in residential landscaping.
The history of Emerald Green Arborvitae traces back to Denmark, where it was introduced in the mid-20th century. It was later brought to North America and gained widespread popularity due to its refined form and adaptability. Unlike faster-growing but larger arborvitae varieties, Emerald Green was bred for its controlled growth habit, making it particularly suitable for smaller gardens and urban settings.
Emerald Green Arborvitae is easily identified by its narrow, columnar shape and dense, rich green foliage that maintains its color throughout the year. The scale-like leaves grow in flat sprays and emit a mild, pleasant fragrance when touched. The tree typically grows to a mature height of 12 to 15 feet and a width of 3 to 4 feet, forming a tight, upright silhouette without the need for pruning. The bark is light brown to reddish and peels in thin strips.
Its growth rate is moderate, typically adding 6 to 9 inches of height per year. While slower than some other arborvitaes like Green Giant, its controlled size is an asset for formal landscapes. With proper care, Emerald Green Arborvitae can live for up to 25 to 40 years, especially when planted in well-drained soil and protected from harsh environmental stressors.
In terms of distribution, this cultivar thrives in regions where its parent species, Thuja occidentalis, also grows well. It is commonly found in nurseries and landscapes across North America, especially in suburban gardens and commercial spaces that value its neat form. It adapts well to various soil types, though it prefers moist, well-drained soils and full sun to partial shade.
Emerald Green Arborvitae grows best in USDA Hardiness Zones 3 through 8, making it suitable for a wide range of climates—from the frigid north to more temperate zones. Its cold hardiness is one of its standout features, allowing it to flourish in areas where other evergreens might struggle in winter.
Other notable facts include its low maintenance needs, resistance to most pests, and minimal pruning requirements. However, it can be susceptible to deer browsing in some areas, unlike Green Giant Arborvitae. It also benefits from mulching and occasional watering during drought to maintain its vigor and appearance. Because of its dense structure, it can also provide modest sound and wind buffering.
Landscape uses of Emerald Green Arborvitae include:
- Narrow privacy screens or hedges
- Foundation plantings along homes or buildings
- Accent plantings in formal garden designs
- Border definition along fences or walkways
- Living walls or green fences in tight spaces
- Framing entrances, gates, or patios
- Noise and visual barriers in small urban lots
- Backdrops for flowering shrubs or perennials
Common Problems Associated with growingEmerald Green Arborvitae (Thuja occidentalis ‘Smaragd’)
Deer damage
– Highly susceptible to deer browsing, especially in winter
– Can result in severe defoliation or death of young trees
Winter burn
– Browning or drying of foliage due to cold winds and sun exposure
– Often affects the south or west side of the tree in late winter
Root rot
– Caused by poorly drained or waterlogged soils
– Leads to yellowing, wilting, and eventual dieback
Drought stress
– Shallow roots make them vulnerable to dry conditions
– Causes browning from the inside out, especially during hot summers
Pest infestations
– Can be affected by spider mites, aphids, or bagworms
– Leads to yellowing, webbing, or thinning foliage
Improper pruning
– Cutting into old wood may result in bare spots that don’t regrow
– Over-pruning can ruin the tree’s natural shape
Poor air circulation
– Planting too close together restricts airflow
– Increases the risk of fungal diseases like needle blight
Salt damage
– Road salt or saline irrigation water can damage roots and foliage
– Leads to browning at the tips and edges of leaves
Transplant shock
– Newly planted trees may experience wilting or stunted growth
– Often caused by root disturbance or poor planting practices
Sunscald on bark
– Occurs during winter when bark heats up in the sun and then freezes
– Can lead to cracks or splits in the trunk
Cultivation of Emerald Green Arborvitae (Thuja occidentalis ‘Smaragd’)
Site Selection
– Choose a location with full sun for best growth and foliage color.
– Though it tolerates partial shade, too much shade can cause thinning and reduced density.
– Avoid low-lying areas where water may pool, as this tree dislikes soggy soil.
Soil Requirements
– Prefers well-drained, loamy soil with moderate moisture.
– It can adapt to a range of soils including sandy or clay types, as long as drainage is adequate.
– Slightly acidic to neutral pH (6.0–8.0) is ideal.
Planting Time
– Best planted in early spring or fall when temperatures are moderate.
– Avoid planting in the heat of summer to reduce transplant shock.
– Fall planting allows roots to establish before winter.
Spacing
– Space trees 3 to 4 feet apart when creating a hedge or screen.
– This allows enough room for air circulation and prevents overcrowding.
– For individual specimens, leave 4 to 5 feet from buildings or structures.
Watering Needs
– Water regularly during the first year until well established.
– Once established, it is moderately drought-tolerant but benefits from watering during dry spells.
– Avoid overwatering to prevent root rot.
Mulching
– Apply a 2- to 3-inch layer of mulch around the base, keeping it away from the trunk.
– Mulch conserves soil moisture, suppresses weeds, and insulates roots.
– Organic mulch like bark or shredded wood is ideal.
Fertilization
– Fertilize in early spring with a slow-release, balanced fertilizer (10-10-10 or 14-14-14).
– Over-fertilization can lead to weak, leggy growth.
– Mature trees typically require less frequent feeding.
Pruning and Shaping
– Minimal pruning is needed due to its natural narrow, columnar form.
– Light shaping can be done in late spring or early summer.
– Avoid cutting into old wood, as it won’t regenerate new growth.
Winter Protection
– Wrap young trees in burlap in harsh winter climates to prevent windburn and snow damage.
– Anti-desiccant sprays can help reduce winter moisture loss.
– Water thoroughly in late fall to hydrate roots before the ground freezes.
Pest Monitoring
– Regularly check for spider mites, aphids, or bagworms, especially in hot and dry periods.
– Neem oil or insecticidal soap can help control infestations.
– Encourage natural predators like ladybugs and birds.
Disease Management
– Ensure good air circulation to prevent fungal issues like tip blight or root rot.
– Avoid overhead watering to keep foliage dry.
– Remove and dispose of infected or dead branches promptly.
Protection from Deer
– Use physical barriers like fencing or netting in areas with deer activity.
– Repellent sprays can offer temporary protection, especially in winter when food is scarce.
– Planting near structures or inside gardens may reduce browsing risk.
Companion Planting and Design
– Combine with other evergreens or deciduous shrubs for contrast and year-round structure.
– Works well as a vertical accent in foundation plantings or formal borders.
– Avoid crowding with aggressive spreading plants that compete for water and nutrients.