Alcock's spruce (Picea bicolor 'Howell's Dwarf')

Overview

Picea bicolor ‘Howell’s Dwarf’, commonly known as Alcock’s spruce, offers gardeners a compact, slow-growing conifer ideal for restricted spaces. This dwarf cultivar features notably dense foliage with attractive bicolor needles: rich green on top and striking silver-blue underneath, providing excellent textural contrast. It is a reliable, tough specimen that performs exceptionally well in cooler climates where many other spruces struggle.

This selection of Alcock’s spruce maintains a dense, spreading, flat-topped habit, although it can develop an irregular pyramidal form if the central leader is allowed to grow unchecked. Expect Picea bicolor ‘Howell’s Dwarf’ to reach 4 to 6 feet in height and 2 to 5 feet in spread relatively slowly, making it a long-term foundation plant. Its tolerance for specific conditions makes it a highly valued evergreen in specialized rockeries or foundation plantings.

Originating from the Japanese mountains, this species, and specifically the ‘Howell’s Dwarf’ cultivar, thrives when provided with consistent moisture and full sun, though it handles light shade. Gardeners should note that Alcock’s spruce generally avoids serious pest issues, contributing to its medium maintenance requirement, allowing it to serve as a sturdy, colorful accent piece year-round.

Fast Facts

• Plant Family: Pinaceae
• Plant Type: Needled evergreen
• Hardiness Zones: USDA Zones 3-7
• Size at Maturity:
  • Height: 4-6 ft
  • Spread: 2-5 ft
• Bloom Time: Non-flowering
• Bloom Description: Non-flowering
• Sun Exposure: Full sun
• Water Needs: Medium
• Maintenance Level: Medium

How to Grow

Plant Picea bicolor ‘Howell’s Dwarf’ during the cooler seasons—spring or fall—to minimize transplant shock, ensuring the root ball is set in average, well-drained soil. The ultimate success of Alcock’s spruce hinges on moisture consistency; while it prefers medium water, excellent drainage is non-negotiable to prevent root issues. Full sun exposure maximizes needle color and density, though it will tolerate light shade.

Water regularly, especially during establishment or periods of drought, ensuring the soil remains evenly moist but never soggy. Fertilization is generally not required unless the soil is exceptionally poor; if you choose to fertilize, use a slow-release evergreen formula applied sparsely in early spring before new growth begins. Pruning is infrequent, mainly limited to removing dead wood or occasionally tipping the central leader to maintain a lower, denser profile.

Gardeners located in hot, humid regions, particularly south of USDA Zone 7, should exercise caution, as this conifer performs best in cooler summer climates. Protect new plantings from drying winter winds, though the mature hardiness of Picea bicolor ‘Howell’s Dwarf’ is quite robust down to Zone 3.

Landscape Uses

The compact yet spreading nature of ‘Howell’s Dwarf’ makes it exceptionally versatile for detailed landscape design. It excels when used as a dwarf mounded evergreen in rock gardens, where its texture and year-round presence provide essential structure against stone elements. Its relatively contained mature size also makes it an excellent choice for foundation plantings where larger shrubs might overwhelm the architecture.

Use Picea bicolor ‘Howell’s Dwarf’ as a specimen or accent plant to draw the eye toward entryways or focal points in smaller yards. Its unique blue-green and green needle contrast pairs beautifully with contrasting foliage colors, such as golden dwarf conifers or broadleaf evergreens with dark, glossy leaves. Consider planting a small collection alongside low-growing, acid-loving perennials that share its cool-climate preference.

Standout Features

Noteworthy Characteristics

Picea bicolor (synonymous with Picea alcoquiana) is an evergreen conifer that is native to a limited but stable number of subalpine forest areas in the mountains of central Japan. It will grow over time to as much as 80’ tall with a broad pyramidal form and spreading branches. The cultivar ‘Howell’s Dwarf’ presents as a spreading flat-topped form; if the central leader is retained, plants may grow irregularly pyramidal to 4-6’ tall over the first decade, while bicolor needles showcase green tops and silvery-blue undersides.

Tolerances

• Deer

Potential Problems

This cultivar is generally robust against serious pests and diseases, often being cited as having no major vulnerabilities. However, watch for common spruce issues, especially when conditions become stressed, such as heavy shade or poor air circulation. Canker, wood decay, needle cast, and rust are fungal issues that may occur if moisture management is poor.

Actively monitor for insect infestations, including aphids, scale insects, bagworms, and spider mites. If pests are spotted, treatments are usually effective when applied according to label directions, often utilizing dormant oils or insecticidal soaps depending on the pest life cycle. Ensuring good airflow and proper soil drainage remains the best preventative strategy for Alcock’s spruce.

Frequently Asked Questions

What hardiness zones is Alcock’s spruce suitable for?

Picea bicolor ‘Howell’s Dwarf’ is recommended for USDA Hardiness Zones 3 through 7.

How large does Picea bicolor ‘Howell’s Dwarf’ grow?

This dwarf cultivar typically matures between 4 to 6 feet tall with a spread of 2 to 5 feet, although size is heavily influenced by whether the central leader is pruned.

What sun exposure does Alcock’s spruce need?

For best performance and color, Picea bicolor ‘Howell’s Dwarf’ requires a location receiving full sun, although it can tolerate some light shade.

When does Alcock’s spruce bloom?

This plant is non-flowering, as is typical for conifers in the Picea genus.

Conclusion

The Picea bicolor ‘Howell’s Dwarf’ provides exceptional year-round texture and color, making it a worthy addition for gardeners seeking a refined, slow-growing evergreen structure. Its preference for cooler summers and well-drained soil means successful placement is key, so always confirm your local USDA zone before planting this beautiful Alcock’s spruce.

Design Ideas

This dwarf spruce shines in mixed conifer plantings where its unique foliage contrasts sharply with nearby plants. Try pairing ‘Howell’s Dwarf’ with plants that demand similar cool, moist, acidic soil, such as dwarf rhododendrons or Japanese maples in early successional stages. Its spreading habit is perfect for softening the edges of retaining walls or stepping stones in a specialized woodland garden layout.

Another powerful application involves using multiple specimens of Picea bicolor ‘Howell’s Dwarf’ at staggered heights along a curved border. This repetition establishes rhythm and texture, leading the eye through the landscape. Because of its relatively slow stature change, it requires minimal shearing to maintain an intentional, mounded shape near pathways or smaller patios where a large tree cannot be accommodated.