How to Grow Thuja Occidentalis
Thuja occidentalis
Thuja occidentalis is one of the most popular hedging conifers in the UK, forming a dense evergreen screen. Plant in full sun for the densest growth and trim twice a year — late spring and late summer — to maintain a neat shape. The critical rule is never to cut back into old brown wood, as it will not regrow. Water regularly during the first two years after planting, and watch for cypress aphid which can cause permanent brown patches if left unchecked. Mulch the base to retain moisture, especially for newly planted hedges.
Yearly Lifecycle
Care Essentials
Apply a balanced slow-release fertiliser in spring and mulch with compost around the base. Avoid overfeeding, which encourages soft frost-prone growth.
Watch For
- Cypress aphid causing permanent brown patches on inner foliage
- Thuja blight (Didymascella) in damp conditions
- Phytophthora root rot on heavy or waterlogged soils
- Scale insects on sheltered hedges
Track your Thuja Occidentalis care schedule — pruning, feeding, and seasonal tasks
Start planning freeCare Requirements
☀️ Light
Full sun for densest growth
Full sun to partial shade. Best colour and density in full sun. Shade causes thin, leggy growth and brown patches.
💧 Watering
Regular when young; drought-tolerant once established
Water regularly during the first two years after planting. Established hedges are fairly drought-tolerant but benefit from watering in prolonged dry spells.
🌱 Fertilizing
Balanced feed in spring with compost mulch
Apply a balanced fertiliser in spring and mulch with compost. Avoid overfeeding which can cause soft, frost-prone growth.
✂️ Pruning
Trim twice yearly; never cut into old wood
Trim twice a year — late spring and late summer — to maintain a neat shape. Never cut back into old brown wood as it will not regrow.
🍂 Mulching
Mulch base to retain moisture
Mulch the base with bark or compost to retain moisture and suppress weeds, especially for newly planted hedges.
Growing Tips
Never cut into old wood
Never cut back into old brown wood — thuja will not regrow from bare stems, leaving permanent gaps in the hedge.
Trim twice yearly
Trim twice a year in late spring and late summer to maintain a neat, dense shape.
Check for cypress aphid
Watch for cypress aphid on inner branches — it can cause permanent brown patches if left unchecked.
Water well when young
Water regularly during the first two years; established hedges are fairly drought-tolerant but benefit from watering in dry spells.
Pests & Diseases
Pest Cypress Aphid
Identification: Greyish-brown aphids on inner branches; sticky honeydew and sooty mould; brown patches in hedge
- Spray inner branches with a strong jet of water to dislodge aphids
- Encourage ladybirds and hoverflies
- Fatty acid spray directed into the interior of the hedge
- Acetamiprid systemic spray for severe infestations
Pest Scale Insects
Identification: Small brown or white waxy bumps on stems and foliage; sticky honeydew; sooty mould
- Scrub off with a soft brush in winter
- Encourage parasitic wasps
- Plant oil-based winter wash
Disease Thuja Blight (Didymascella) Didymascella thujina
Symptoms: Brown or black patches on foliage, starting on lower and inner branches; affected foliage turns brown and dies
Treatment: Prune out and destroy affected branches. Improve air circulation within the hedge.
Prevention: Avoid planting too closely. Trim to allow light and air into the interior. Avoid overhead watering.
Disease Phytophthora Root Rot Phytophthora spp.
Symptoms: Yellowing and browning of foliage in sections; progressive dieback; dark discolouration at stem base
Treatment: Remove and destroy affected plants. Improve drainage. Do not replant thuja in the same spot.
Prevention: Ensure well-drained soil. Avoid waterlogged sites. Do not plant too deep.
Spacing & Planting
| Plant spacing | 80 cm |
| Row spacing | 100 cm |
| Mature height | 500 cm |
| Mature spread | 200 cm |
Eastern Arborvitae, the most common hedging thuja. Grows 3-5m in hedge form. Popular cultivars include Brabant and Smaragd. Trim in late spring and late summer. Avoid cutting into old wood. Prefers moist, well-drained soil.
Log Thuja Occidentalis in your garden — track growth, care, and harvests year after year
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