Green Mountain Boxwood (Buxus x ‘Green Mountain’)

Green Mountain Boxwood, also known as Buxus x ‘Green Mountain’, and commonly referred to as simply Green Mountain Boxwood or Korean Boxwood hybrid, is a versatile evergreen shrub celebrated for its vibrant green foliage and pyramidal form. This popular choice for formal hedges, topiary, and foundation plantings offers year-round interest and relatively easy maintenance.

This comprehensive guide will cover everything from how to care for Green Mountain Boxwood, including identifying and addressing potential diseases, to mastering pruning techniques for optimal shape and health. We’ll also explore where to buy Green Mountain Boxwood plants and compare this popular cultivar to other boxwood varieties. Keep reading to unlock the secrets to successfully growing and enjoying this beautiful shrub.

Understanding Green Mountain Boxwood: Characteristics and Benefits

Before diving into planting and care, it’s essential to understand the specific characteristics that make Green Mountain Boxwood a standout choice. This section provides a detailed overview, helping you decide if it’s the right fit for your landscape.

Common name	Green Mountain Boxwood, Korean Boxwood Hybrid
Botanical name	Buxus x ‘Green Mountain’
Family	Buxaceae
Genus	Buxus
Species	Hybrid ( B. sempervirens x B. sinica var. insularis)
Origin	Hybrid origin
Native	Not native to a specific region; a cultivated hybrid
Life cycle	Perennial
Plant type	Broadleaf Evergreen Shrub
Hardiness zone	5, 6, 7, 8, 9
Sunlight	Full Sun, Partial Shade
Maintenance	Low to Moderate
Water	Moderate (Drought-tolerant once established)
Drainage	Well-Drained
Spacing	2-3 ft. (for hedges, closer spacing is acceptable)
Flowering period	Spring (Insignificant flowers)
Height	4-5 ft. (typical, can vary with pruning)
Width	2-3 ft.
Growth rate	Slow to Moderate
Flower color	Greenish-white (Insignificant)
Foliage color	Bright Green
Stem color	Green, maturing to light brown
Flower benefit	Not significant for flowering
Garden style	Formal, Contemporary, Cottage, City
Uses	Hedges, Topiary, Foundation Planting, Container, Borders, Mass Planting, Accent Plant
Deer Resistance	Yes
Toxicity	Mildly toxic to pets if ingested
Drought Tolerance	Good, once established
Soil pH	Slightly Acidic to Neutral (6.5-7.2)
Propagation	Stem Cuttings
Pruning Season	Late Winter to Early Spring
Pest and Disease issues	Boxwood Blight (potential), Boxwood Leafminer (potential), Boxwood Psyllid (potential), Phytophthora Root Rot (potential)

• Botanical Classification and Origin: Green Mountain Boxwood is a hybrid cultivar, a cross between Buxus sempervirens (English Boxwood) and Buxus sinica var. insularis (Korean Boxwood). This parentage gives it a desirable combination of cold hardiness and a classic boxwood appearance. It was developed to withstand colder climates better than many other boxwood varieties.
• Growth Habit and Size: Green Mountain Boxwood exhibits a naturally upright, pyramidal growth habit. This makes it ideal for creating formal hedges and geometric shapes without excessive pruning. Mature plants typically reach a height of 4-5 feet and a width of 2-3 feet, although this can vary depending on growing conditions and pruning practices.
• Foliage: The foliage is its defining characteristic. The small, oval-shaped leaves are a vibrant, glossy green, maintaining their color throughout the year, even in winter. This evergreen nature provides year-round visual interest in the landscape. The dense foliage also provides excellent screening and privacy.
• Hardiness Zones: Green Mountain Boxwood is remarkably hardy, thriving in USDA Hardiness Zones 5-9. This broad range makes it suitable for a wide variety of climates across the United States and other temperate regions. This hardiness is a significant advantage over some more sensitive boxwood varieties.
• Sunlight Requirements: This cultivar prefers full sun to partial shade. While it can tolerate some shade, optimal growth and the richest foliage color are achieved with at least 4-6 hours of direct sunlight per day. In hotter climates, some afternoon shade can be beneficial to prevent leaf scorch.
• Soil Preferences: Well-drained soil is crucial for the health of Green Mountain Boxwood. It prefers slightly acidic to neutral soil (pH 6.5-7.2). Heavy clay soils should be amended with organic matter, such as compost or peat moss, to improve drainage. Poor drainage can lead to root rot, a common problem for boxwoods.
• Deer Resistance: A significant benefit of Green Mountain Boxwood is its deer resistance. Deer typically avoid browsing on boxwood, making it a valuable choice for gardens where deer are a problem. This is due to the presence of alkaloids in the foliage, which are unpalatable to deer.
• Drought Tolerance: Once established, Green Mountain Boxwood exhibits good drought tolerance. However, regular watering is essential during the first few years after planting to help the root system develop.
• Uses in Landscape
  • Formal hedges: This plant is a traditional choice.
  • Foundation plantings: The evergreen foliage can be utilized year-round.
  • Topiary: Create geometric shapes and whimsical designs.
  • Container gardening: Ideal for patios, decks, and entryways.

Planting Green Mountain Boxwood: A Step-by-Step Guide

Planting your Green Mountain Boxwood correctly is the foundation for its long-term health and success. Follow these steps for optimal results:

1. Timing: The best time to plant Green Mountain Boxwood is in the spring or fall. This allows the plant to establish its roots before the extremes of summer heat or winter cold. Avoid planting during periods of extreme heat or drought.
2. Site Selection: Choose a location that meets the sunlight and soil requirements outlined above (full sun to partial shade, well-drained soil). Consider the mature size of the plant when selecting a location, ensuring it has enough space to grow without overcrowding.
3. Soil Preparation: Before planting, amend the soil with compost or other organic matter to improve drainage and fertility. This is especially important for heavy clay soils. A soil test can help determine the pH and nutrient levels, allowing you to make any necessary adjustments.
4. Digging the Hole: Dig a hole that is twice as wide as the root ball and just as deep. This provides ample space for the roots to spread and grow.
5. Removing the Plant from the Container: Gently remove the plant from its container, being careful not to damage the roots. If the roots are tightly bound (root-bound), gently loosen them with your fingers or a small hand rake.
6. Planting Depth: Place the plant in the hole so that the top of the root ball is level with or slightly above the surrounding soil. Planting too deeply can lead to root rot.
7. Backfilling: Backfill the hole with the amended soil, gently firming it around the roots to eliminate air pockets. Avoid compacting the soil too tightly, as this can restrict root growth.
8. Watering: Water the newly planted boxwood thoroughly, saturating the root zone. This helps settle the soil and encourages root establishment.
9. Mulching: Apply a 2-3 inch layer of organic mulch, such as shredded bark or wood chips, around the base of the plant. Mulch helps conserve moisture, suppress weeds, and regulate soil temperature. Keep the mulch a few inches away from the stem to prevent rot.
10. Staking (if necessary): If planting in a windy location or if the plant is top-heavy, staking may be necessary to provide support until the roots are established. Use soft ties to secure the plant to the stakes, avoiding tight constrictions that can damage the stem.

How to Care for Green Mountain Boxwood: Watering, Fertilizing, and More

Consistent care is crucial for maintaining the health and beauty of your Green Mountain Boxwood. This section covers essential care practices.

• Watering:
  • Establishment Phase (first year): Water deeply and regularly, especially during dry periods. Aim to keep the soil consistently moist but not waterlogged.
  • Established Plants: Once established, Green Mountain Boxwood is relatively drought-tolerant. However, supplemental watering may be necessary during prolonged dry spells, particularly in hot climates. Water deeply and less frequently, allowing the soil to dry slightly between waterings.
  • Watering Techniques: Use a soaker hose or drip irrigation to deliver water directly to the root zone, minimizing water loss through evaporation and reducing the risk of foliar diseases. Avoid overhead watering, which can wet the foliage and create favorable conditions for fungal growth.
• Fertilizing:
  • Timing: Fertilize Green Mountain Boxwood in early spring, before new growth begins.
  • Fertilizer Type: Use a balanced, slow-release fertilizer formulated for evergreen shrubs. A granular fertilizer with an N-P-K ratio of 10-10-10 or similar is generally suitable. Alternatively, you can use a fertilizer specifically designed for acid-loving plants, as boxwoods prefer slightly acidic soil.
  • Application: Follow the manufacturer’s instructions carefully, applying the fertilizer evenly around the base of the plant and extending out to the drip line (the area directly beneath the outer edge of the branches). Avoid applying fertilizer directly to the stems or foliage, as this can cause burning.
  • Soil Testing: A soil test can provide valuable information about nutrient levels and pH, allowing you to tailor your fertilization program to the specific needs of your plants.
• Mulching (Maintenance): Replenish the mulch layer annually in spring or fall to maintain a 2-3 inch depth. This helps conserve moisture, suppress weeds, and regulate soil temperature.
• Winter Protection: In colder climates (Zones 5 and 6), it’s beneficial to protect Green Mountain Boxwood from winter damage, especially during the first few years after planting.
  • Anti-desiccant Spray: Apply an anti-desiccant spray to the foliage in late fall or early winter. This helps reduce moisture loss from the leaves during harsh winter winds and freezing temperatures.
  • Burlap Wrap: Wrap the plant with burlap or other protective material to shield it from wind and sunscald.
  • Snow Removal: Gently remove heavy snow from the branches to prevent breakage.

Pruning Techniques for Green Mountain Boxwood

Pruning is essential for maintaining the shape, size, and health of Green Mountain Boxwood. Here’s a guide to proper pruning techniques:

• Timing: The best time to prune Green Mountain Boxwood is in late winter or early spring, before new growth begins. This allows you to shape the plant before it starts actively growing and also provides good visibility of the branches. Avoid pruning in late summer or early fall, as this can stimulate new growth that may not harden off before winter, making it susceptible to cold damage.
• Tools: Use sharp, clean pruning tools to make clean cuts and prevent the spread of diseases.
  • Hand Pruners: For small branches (up to ½ inch in diameter).
  • Loppers: For medium-sized branches (up to 1 ½ inches in diameter).
  • Hedge Shears: For shaping hedges and creating formal shapes.
  • Pruning Saw: For larger branches (over 1 ½ inches in diameter).
• Pruning Techniques:
  • Thinning: Thinning involves removing entire branches back to their point of origin or to a lateral branch. This opens up the interior of the plant, improving air circulation and light penetration, which helps reduce the risk of diseases and promotes healthy growth.
  • Heading Back: Heading back involves cutting back a branch to a bud or a lateral branch. This encourages bushier growth and can be used to control the size and shape of the plant.
  • Shearing: Shearing involves using hedge shears to create a formal, uniform shape. This is commonly used for hedges and topiary. Avoid shearing too frequently, as it can lead to a dense outer layer of foliage that shades the interior of the plant.
  • Rejuvenation Pruning: If you have an older plant, this technique can be used to restore the plant.
• General Pruning Guidelines:
  • Remove Dead, Damaged, or Diseased Wood: Always start by removing any dead, damaged, or diseased branches. This improves the overall health and appearance of the plant.
  • Prune to Maintain Natural Shape: Green Mountain Boxwood has a naturally pyramidal shape. Prune to enhance this shape rather than trying to force it into an unnatural form.
  • Don’t Remove Too Much Foliage: Avoid removing more than one-third of the plant’s foliage at any one time. Over-pruning can stress the plant and make it more susceptible to diseases.
  • Step Back and Evaluate: Periodically step back from the plant to evaluate your progress and ensure you’re achieving the desired shape.

Identify Diseases and Pests of Green Mountain Boxwood

While Green Mountain Boxwood is generally resistant to pests and diseases, it can occasionally be affected by certain problems. Early identification and treatment are crucial for minimizing damage.

• Boxwood Blight: This is a serious fungal disease that has become increasingly prevalent in recent years.
  • Symptoms: Leaf spots (tan or brown with dark borders), black streaks on stems, leaf drop, and dieback.
  • Cause: Calonectria pseudonaviculata (formerly Cylindrocladium buxicola) fungus.
  • Prevention: Avoid overhead watering, improve air circulation through thinning, plant resistant cultivars, and practice good sanitation (remove fallen leaves and debris).
  • Treatment: Fungicides can help prevent the spread of the disease, but they will not cure infected plants. Severely infected plants should be removed and destroyed.
• Boxwood Leafminer: This is a common pest that can cause significant damage to boxwood foliage.
  • Symptoms: Blistered or mined leaves (yellow or brown patches between the leaf surfaces), premature leaf drop.
  • Cause: The larvae of the boxwood leafminer fly (Monarthropalpus flavus) feed inside the leaves.
  • Prevention: Maintain healthy plants, as stressed plants are more susceptible to infestation.
  • Treatment: Systemic insecticides can be effective in controlling leafminer larvae. Apply in spring when the adult flies are active. Horticultural oil can also be used to smother the eggs.
• Boxwood Psyllid: This pest causes cupping and curling of new growth.
  • Symptoms: Cupped or curled new leaves, waxy white secretions.
  • Cause: The nymphs of the boxwood psyllid (Psylla buxi) feed on the sap of new growth.
  • Prevention: Maintain healthy plants.
  • Treatment: Insecticidal soap or horticultural oil can be effective in controlling psyllids. Apply when the nymphs are active in spring.
• Phytophthora Root Rot: This is a soilborne fungal disease that can be fatal to boxwoods, especially in poorly drained soils.
  • Symptoms: Yellowing or browning of foliage, wilting, dieback, and eventual plant death.
  • Cause: Phytophthora species fungi.
  • Prevention: Plant in well-drained soil, avoid overwatering, and improve drainage in heavy clay soils.
  • Treatment: There is no effective cure for Phytophthora root rot. Prevention is key.
• Spider Mites:
  • Symptoms: Yellow/bronzed leaves, webbing
  • Cause: Spider Mites
  • Prevention: Strong and healthy plant.
  • Treatment: Insecticidal Soap

Comparing Green Mountain Boxwood to Other Cultivars

Green Mountain Boxwood is a popular choice, but it’s not the only boxwood cultivar available. Understanding the differences between various cultivars can help you select the best one for your specific needs.

Feature	Green Mountain Boxwood	Wintergreen Boxwood	Japanese Boxwood	English Boxwood
Botanical Name	Buxus x ‘Green Mountain’	Buxus sinica var. insularis ‘Wintergreen’	Buxus microphylla var. japonica	Buxus sempervirens
Growth Habit	Upright, pyramidal	Rounded, spreading	Rounded, compact	Dense, rounded
Mature Size	4-5 ft tall, 2-3 ft wide	2-4 ft tall, 3-5 ft wide	3-6 ft tall, 3-6 ft wide	Varies greatly by cultivar
Hardiness Zones	5-9	4-9	6-9	5-8
Leaf Color	Bright green	Light green	Dark green	Dark green
Growth Rate	Moderate	Slow	Moderate	Slow
Cold Hardiness	Excellent	Excellent	Good	Moderate
Deer Resistance	Yes	Yes	Yes	Yes
Common Uses	Hedges, topiary, foundation	Hedges, borders, foundation	Hedges, borders, mass planting	Hedges, topiary

Key Differences and Considerations:

• Wintergreen Boxwood: Known for its exceptional cold hardiness, even extending into Zone 4. It has a more rounded and spreading growth habit compared to Green Mountain’s pyramidal form.
• Japanese Boxwood: Generally more tolerant of heat and humidity than other boxwoods. It has a faster growth rate than English Boxwood and a more rounded, compact form.
• English Boxwood: The classic boxwood, often used for formal hedges and topiary. It has a slower growth rate and a more dense, rounded habit. It can be more susceptible to boxwood blight than some other cultivars.
• Other Notable Cultivars:
  • ‘Dee Runk’: Columnar Growth
  • ‘Fastigiata’: Upright form
  • ‘Graham Blandy’: Narrow, columnar.

When choosing a boxwood cultivar, consider your climate, desired size and shape, and any specific pest or disease concerns in your area. Green Mountain Boxwood is a strong all-around choice, especially for colder climates and where a formal, pyramidal shape is desired.