How to Grow Western Red Cedar: A Comprehensive Guide for Beginners
Introduction
Western red cedar (Thuja plicata) is a majestic conifer tree native to western North America. It’s a popular choice for hedging in UK gardens due to its attractive evergreen foliage and fast growth rate. This guide will provide you with all the information you need to successfully grow and care for western red cedar in your own garden.
Identifying Western Red Cedar
Thuja plicata has distinctive scale-like leaves arranged in flat sprays. When crushed, the leaves release an aromatic, pineapple-like scent. The tree naturally forms a tall, conical shape with drooping branches covered in mid-green leaves. In summer and autumn, it produces clusters of small, flattened oval brown cones.
Size, Height, and Spread
Thuja plicata and its popular hedging variety, Thuja plicata Atrovirens, have a moderate growth rate of 45-60cm per year. Regular trimming can keep a western red cedar hedge compact, as low as 1.5-2m high. Left untrimmed, it can reach a mature height of 35m and a spread of 7-10m. Compact-growing varieties are smaller, typically reaching 2.5m high and 1.5m wide.
Value to Wildlife
Western red cedar hedges and mature trees provide nesting sites for birds and shelter for other wildlife.
How to Grow Thuja Plicata
Soil and Planting:
- Thuja plicata thrives in fertile, moisture-retentive soil.
- Avoid waterlogged or dry ground.
- Plant in sun or shade, but avoid exposed sites with cold winds.
- Space hedge plants 60-75cm apart.
- Plant at least a meter away from property boundaries for hedge growth and trimming access.
- Keep hedges at least five meters from houses to prevent damage from root growth.
Watering:
- Water regularly during dry spells, especially in the first two growing seasons.
- Avoid over-watering, as thuja can suffer in wet ground.
Care:
- Mulch around the root area annually to maintain soil moisture and protect roots.
- Protect young plants from cold, drying winds.
- Mature Thuja plicata requires minimal care.
How to Prune Thuja Plicata
- Use a hedge trimmer or shears to trim the top and sides of a hedge two to three times during the growing season.
- Avoid pruning during nesting season (spring-early summer), or check for birds before pruning.
- Trim on overcast days to prevent foliage scorch.
- Slope the sides of the hedge to allow even light distribution and drainage.
- Avoid trimming the top too severely; cut around a third to a half of the growth from the sides.
- Wear gloves and clothing that covers arms and legs when pruning to avoid skin irritation.
Pests and Diseases
Thuja Blight:
- Caused by a fungal disease, thuja blight can affect young trees and browning of foliage in older trees.
- Cut out and dispose of affected foliage and collect fallen leaves.
Conifer Aphid and Scale Insect:
- These insects can cause yellowing or mottling of leaves.
- Encourage natural predators and maintain a balanced ecosystem to control infestations.
Varieties of Thuja Plicata
Thuja plicata Atrovirens:
- Popular for hedging, sold as either western red cedar or by its botanical name.
- Height x Spread: 35m x 1m (untrimmed)
Thuja plicata Can-Can:
- Semi-dwarf variety with slow growth and dark green foliage.
- Perfect for specimen trees or slow-growing hedges.
- Height x Spread: 2.5m x 1m (untrimmed)
Thuja plicata Goldy:
- Golden foliage that turns orange in winter, providing color.
- Height x Spread: 6m x 1m (untrimmed)
Thuja plicata Stoneham Gold:
- Striking specimen tree with dark green inner foliage and golden yellow outer foliage.
- Slow growing.
- Height x Spread: 1.8m x 90cm (untrimmed)
Thuja plicata Whipcord:
- Unusual foliage with a ‘braided’ appearance, green in summer and bronze in winter.
- Forms a low weeping dome shape.
- Ideal for rockeries.
- Height x Spread: 1.8m x 90cm (untrimmed)