Western red cedar (Thuja plicata 'Cuprea')

Overview

Thuja plicata ‘Cuprea’, often called Western red cedar, is a highly desirable dwarf cultivar prized for its manageable size and interesting color shifts. This cultivar maintains the classic appeal of the species while fitting elegantly into smaller garden spaces where the massive native tree would dominate. Gardeners appreciate the dense structure and aromatic foliage that remains attractive year-round.

This needled evergreen prefers cool, moist environments, reflecting its native habitat in the Pacific Northwest. While it is adaptable enough for moderate climates, successful cultivation of Thuja plicata ‘Cuprea’ demands attention to consistent moisture and well-drained soil structure. It offers year-round texture and structure, making it a reliable anchor plant in structured landscapes.

The compact habit of Thuja plicata ‘Cuprea’ makes it exceptionally functional for foundation plantings or rock gardens, providing excellent evergreen screening without excessive height. Its unique foliage, tipped with light yellow variegation that deepens to copper in winter, ensures dynamic visual interest across all seasons.

Fast Facts

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

How to Grow

Planting should ideally occur in spring or fall when temperatures are moderate, allowing the roots of this Western red cedar variety to establish before facing temperature extremes. Ensure the location provides fertile, well-drained soil rich in organic matter. Good drainage is non-negotiable, as saturated soil can quickly lead to root issues for Thuja plicata ‘Cuprea’.

Maintain medium water needs by providing consistent moisture, especially during dry spells, as this conifer is intolerant of dry conditions. While it tolerates full sun, providing light afternoon shade in hotter summer climates will help prevent scorching and maintain foliage quality. Fertilization is rarely necessary if the soil is fertile; focus on heavy mulching to retain soil moisture and regulate root temperature.

Pruning for shape or size control is usually minimal due to the natural slow, rounded growth habit of this dwarf cultivar. Be mindful that this plant may struggle in continental climates drastically different from its cool, damp native area; monitoring for stress is key during establishment.

Landscape Uses

Thuja plicata ‘Cuprea’ excels where space is limited but evergreen presence is desired. Its recommended uses explicitly include functioning effectively as a low hedge, providing structure along borders, or softening hardscaping foundations. Furthermore, its tolerance for wetter conditions makes the Western red cedar an excellent choice for rain gardens, integrating beauty with water management.

For rock gardens, the slow-growing, rounded form of this Thuja provides wonderful contrast against coarse stone textures. When planning a foundation planting, place it where its future 4-foot height will not obscure lower windows while ensuring it receives adequate light for best color display.

Standout Features

Noteworthy Characteristics

Thuja plicata, commonly called western red cedar or giant red cedar, is native to the Pacific Northwest where it is typically found in cool but moist forest areas and bottomlands from southern Alaska along the Pacific coast to northern California and in the northern Rockies from British Columbia to Montana. This is the largest tree in the cypress family, growing in its native habitat to 100-200’ tall and living from 400 to 1000+ years. It features horizontal branching with sprays of scale-like dark green foliage that is aromatic when crushed. Fibrous, aromatic, reddish-brown bark. Small, upright, light brown seed cones (to 1/2” long).Genus name is the Greek name for a kind of juniper (Juniperus.)Specific epithet means pleated.‘Cuprea’ is a dwarf, rounded, western red cedar that grows to only 2’ tall and as wide during the first 10 years, eventually maturing over time to 4’ tall by 5’ wide. Foliage is green tipped with light yellow variegation. Foliage turns copper yellow in winter.

Tolerances

• Clay Soil
• Black Walnut

Potential Problems

While generally robust against major issues, gardeners should be vigilant regarding common conifer ailments. Potential problems include occurrences of bagworms, which can defoliate branches, and various root rots if soil drainage becomes inadequate over time. If environmental conditions, such as excessive heat or drought typical in non-native regions, stress the plant, its susceptibility to secondary issues increases, so maintaining ideal moisture levels is the key preventative measure for this Western red cedar.

Frequently Asked Questions

What hardiness zones is Thuja plicata ‘Cuprea’ suitable for?

This dwarf Western red cedar is suitable for USDA Hardiness Zones 5 through 7, requiring protection or careful placement outside these ranges.

How large does Thuja plicata ‘Cuprea’ grow?

Thuja plicata ‘Cuprea’ typically reaches a mature height between 2 and 4 feet, with a spread ranging from 2 to 5 feet wide.

What sun exposure does Western red cedar need?

This variety performs best in areas receiving full sun to partial shade, appreciating some relief from intense afternoon sun in the hottest parts of the day.

When does Thuja plicata ‘Cuprea’ bloom?

As a needled evergreen, Thuja plicata ‘Cuprea’ is non-flowering and does not produce noticeable blooms.

Conclusion

For gardeners seeking manageable size combined with year-round texture and interesting seasonal color, Thuja plicata ‘Cuprea’ provides an excellent solution. This dwarf Western red cedar offers unique foliage that transitions beautifully into winter copper tones. Before planting, confirm your location falls within USDA Zones 5-7 and ensure soil moisture requirements are consistently met to enjoy this specimen for years.

Design Ideas

The compact, rounded habit of Thuja plicata ‘Cuprea’ makes it an indispensable structural element in mixed borders, particularly contemporary or woodland-style plantings. Use it as an “evergreen filler” plant nestled between deciduous shrubs, providing necessary winter interest when other plants are dormant. Since it eventually reaches 5 feet wide, mass plantings create an effective, low, evergreen groundcover or border edge that softens pathways.

When designing around this cultivar, consider its light requirements; placing it near taller shrubs that offer dappled afternoon shade will enhance the yellow variegation on its foliage without causing stress in hot climates. For rock gardens, its slow growth rate ensures it won’t quickly overwhelm smaller companion plants like low-growing sedums or creeping phlox.

Companion Planting

Given that Thuja plicata ‘Cuprea’ thrives in moisture-retentive, fertile soils, pair it with compatible acid-loving plants that share similar water needs. Excellent companions include a variety of low-growing ferns (e.g., Japanese Painted Fern) which appreciate the shade provided by the cedar’s tiered branches, and moisture-loving woodland groundcovers like Epimedium or Hosta varieties that tolerate partial sun. Avoid pairing high-drought tolerant species, as the Western red cedar will require consistent watering that might over-saturate desert-adapted plants.