Boxwood (Buxus sempervirens 'Dee Runk')

Overview

The columnar Boxwood, specifically the variety Buxus sempervirens ‘Dee Runk’, offers exceptional formal structure in a narrow footprint, making it a highly sought-after broadleaf evergreen. Unlike its wider relatives, this selection grows upright, reaching heights up to 10 feet while maintaining a tight spread of only 2 to 3 feet. This density and shape make the Buxus sempervirens ‘Dee Runk’ invaluable for creating formal lines where horizontal space is limited.

This Boxwood thrives in Southern European climates, typically suited for USDA Hardiness Zones 6 through 8. It provides year-round deep, glossy green color, which is crucial for winter interest in the landscape. While it tolerates significant shade, optimal health and density are achieved with morning sun exposure, minimizing the risk of winter foliage scorch.

For gardeners needing vertical accents or material for narrow hedging, Buxus sempervirens ‘Dee Runk’ delivers traditional Boxwood beauty without the extensive trimming required by rounder cultivars. Proper siting and consistent medium water levels ensure this evergreen remains a stately, low-to-medium maintenance feature throughout the seasons.

Fast Facts

• Plant Family: Buxaceae
• Plant Type: Broadleaf evergreen
• Hardiness Zones: USDA Zones 6-8
• Size at Maturity:
  • Height: 8-10 ft
  • Spread: 2-3 ft
• Bloom Time: April to May
• Bloom Description: Creamy white
• Sun Exposure: Full sun to part shade
• Water Needs: Medium
• Maintenance Level: Medium

How to Grow

Plant the Buxus sempervirens ‘Dee Runk’ during the cooler months—spring or fall—to minimize transplant shock, ensuring it establishes firm roots before summer heat or deep winter freezes. The Boxwood prefers evenly moist, well-drained loam soils, which can be a sand-clay mixture. While it adapts to various light conditions, locate it where it receives protection from harsh, drying winter winds and intense afternoon sun, which can cause foliage to bronze or scorch.

Maintain consistently moist soil conditions, especially during establishment; the water needs of this Boxwood are medium. Avoid cultivating deeply around the base of the plants, as they possess shallow root systems. Instead, apply a 1- to 2-inch layer of organic mulch, such as compost or bark, to conserve moisture and moderate soil temperatures.

Pruning and shearing should be deferred until after the last predicted spring frost date. Pruning earlier encourages tender new growth that is highly susceptible to damage from late frosts. Annually thin the canopy slightly to improve air circulation within the dense foliage, which helps deter fungal issues common to Boxwood plantings.

Landscape Uses

The columnar habit of Buxus sempervirens ‘Dee Runk’ makes it an exceptional choice where verticality is required in tight spaces. Mass planting is ideal for creating a narrow, formal hedge that defines pathways or screens undesirable views without consuming excessive garden width. Due to its elegant, structured form, this selection performs beautifully as a vertical specimen near entryways or within formal gardens reminiscent of Mediterranean designs.

It integrates seamlessly into mixed beds and borders, offering strong evergreen contrast against softer perennials or deciduous shrubs. Furthermore, this Boxwood is highly suitable for use as a topiary subject, maintaining sharp lines even with standard shearing. For those gardening on patios or balconies, the ‘Dee Runk’ maintains its formal presence nicely when placed in large containers.

Standout Features

Flower Qualities

• Insignificant

Noteworthy Characteristics

The species Buxus sempervirens is historically significant, with its dense wood historically used for making boxes, hence the common name Boxwood. This cultivar, ‘Dee Runk’, maintains the evergreen status and glossy dark green leaves typical of the species but is distinguished by its narrow, columnar growth pattern and slow rate of spread, reaching up to 10 feet tall while remaining slender. Discovered at the Blandy Experimental Farm, this selection is named in honor of Benjamin F. D. Runk, a noted biologist.

Tolerances

• Rabbit
• Deer

Potential Problems

The primary aesthetic issue for Buxus sempervirens ‘Dee Runk’ is winter bronzing, where foliage turns an unattractive yellowish-brown shade. This typically strikes plants exposed to full winter sun and drying winds, causing dehydration. To mitigate this, site the plant in a location sheltered from western exposure if possible, and ensure consistent moisture leading into winter.

Fungal diseases pose ongoing threats, particularly Boxwood blight, volutella blight, and leaf spot, which thrive in humid, stagnant conditions. Proper maintenance, including annual thinning to maximize air flow and avoiding overhead spring watering, is essential for prevention. Poorly drained soils lead to root rot, emphasizing the need for well-draining site preparation.

Insect pests like the boxwood leafminer, mite, and psyllid require vigilance. Inspect new growth regularly for signs of infestation. While deer and rabbits generally avoid this plant, nematodes can cause slow decline, necessitating good soil health practices to support the plant’s overall vigor.

Frequently Asked Questions

What hardiness zones is Boxwood (Buxus sempervirens ‘Dee Runk’) suitable for?

Buxus sempervirens ‘Dee Runk’ is suitable for planting in USDA Hardiness Zones 6 through 8.

How large does Boxwood grow?

Mature specimens typically reach 8 to 10 feet in height, with a notably narrow spread of only 2 to 3 feet.

What sun exposure does Boxwood need?

This Boxwood performs best in full sun to part shade conditions, though it can survive in deeper shade, albeit with less vigorous growth.

When does Boxwood bloom?

The inconspicuous creamy white flowers appear relatively early in the season, generally between April and May.

Conclusion

The Buxus sempervirens ‘Dee Runk’ provides invaluable formal structure through its dense, glossy evergreen foliage and tight columnar habit, perfect for modern or traditional landscapes needing vertical definition. Considering its medium maintenance needs and deer/rabbit resistance, this Boxwood is a reliable performer. Always confirm your location falls within USDA Zones 6-8 and plant it in a spot with good drainage before the next growing season.

Companion Planting

When planning borders featuring Buxus sempervirens ‘Dee Runk’, selecting companions that share similar medium-water needs and a preference for well-drained soil is key. Consider pairing the strong vertical lines of this Boxwood with mounding plants like Hosta (in shadier spots) or low, spreading Sedum varieties for textural contrast. For a formal look, integrate low-growing perennials such as Lavender or Catmint along the front of the hedge line, provided they receive adequate sun exposure.

Propagation Tips

As a desirable cultivar, Buxus sempervirens ‘Dee Runk’ is typically propagated asexually, most commonly via cuttings to ensure genetic fidelity to the columnar form. Softwood or semi-hardwood cuttings taken during the early summer months provide the highest rate of success. Select healthy stems that are 4 to 6 inches long, strip the lower leaves, and dip the base in rooting hormone before placing them in a moist, well-draining propagation medium under high humidity.