Soil & potting mix
Best soil for Western Red Cedar (Thuja plicata)
Also called Western Red Cedar, Giant Arborvitae, Giant Cedar, Pacific Red Cedar.
More about western red cedar
About Western Red Cedar
Thuja plicata · also called Western Red Cedar, Giant Arborvitae · flowering
Western Red Cedar is a majestic, fast-growing conifer native to the Pacific Northwest, one of the most important timber and cultural trees of the region. Its graceful, drooping branchlets carry flat, glossy, aromatic scale-like foliage. Adaptable to a wide range of soils, it makes an excellent large specimen, windbreak, or privacy hedge in zones 5–9.
Preferred mix: Moist, well-drained to moderately wet, slightly acidic loam or clay loam
Watch for — Windburn and Winter Desiccation: Exposed plants in zones 5–6 can suffer browning of foliage from cold, dry winter winds drawing moisture from foliage faster than frozen roots can replace it. Apply anti-desiccant spray in late autumn; shelter young trees with burlap windbreaks in their first 2 winters.
Why western red cedar needs this mix
Western Red Cedar is a Mediterranean dry-hillside plant — it wants a lean, sharply drained, slightly alkaline mix, and rots fast in rich, water-holding soil.
- Western Red Cedar evolved on stony, sun-baked slopes — its roots expect to dry out hard and quickly between rains, so the mix must drain almost as fast as you pour.
- A lean, low-nutrient mix keeps growth firm and aromatic; a rich one gives soft, sappy, flavourless growth that flops and rots.
- It tolerates and often prefers a slightly alkaline soil, the opposite of most houseplants.
For the full picture on what makes up a good mix, see our guide to the main types of soil and potting media — it explains why each ingredient above behaves the way it does.
What goes wrong with the wrong mix
The wrong soil is one of the most common reasons western red cedar struggles, and the damage often shows up weeks later as a watering problem. For this species specifically:
- Rich, moisture-holding compost is the classic killer of western red cedar — especially over a cold, wet winter, when the base of the plant simply rots.
- A peaty, acidic potting mix is doubly wrong: too wet and the wrong pH direction.
- No grit means the rootball stays damp for days, which a dry-climate root system never copes with.
Growing western red cedar in ordinary rich, moisture-retentive compost. Lean it out with at least a third grit, and never let it sit wet over winter.
pH — does it matter for western red cedar?
Western Red Cedar likes neutral to slightly alkaline soil, roughly pH 6.5-7.5. If your soil or compost is acidic, a little garden lime or extra grit nudges it the right way — the one common plant where you may add lime.
If you want to check or adjust it, the soil pH guide walks through testing and the safe ways to nudge a mix more acidic or more alkaline.
DIY mix vs a bagged one
Bagged "herb" or "Mediterranean" mixes are usually fine for western red cedar, but most standard composts need cutting hard with grit. The DIY ratio above is cheap and exactly right.
Drainage and the pot
Sharp drainage is everything: a terracotta pot with a big hole, gritty mix and never a saucer left full. Raised beds suit these herbs outdoors for the same reason.
A gritty mix barely breaks down, so western red cedar needs little repotting — refresh the top layer and the grit every couple of years rather than potting on aggressively. When the time comes, our repotting guide for western red cedar covers the timing and technique step by step.
Western Red Cedar soil — frequently asked questions
What is the best soil mix for western red cedar?
2 parts standard peat-free compost or loam : 1 part coarse horticultural grit : 1 part perlite or coarse sand. Western Red Cedar evolved on stony, sun-baked slopes — its roots expect to dry out hard and quickly between rains, so the mix must drain almost as fast as you pour.
Can I use normal potting soil for western red cedar?
Rich, moisture-holding compost is the classic killer of western red cedar — especially over a cold, wet winter, when the base of the plant simply rots. Bagged "herb" or "Mediterranean" mixes are usually fine for western red cedar, but most standard composts need cutting hard with grit. The DIY ratio above is cheap and exactly right.
Does western red cedar need a special pH?
Western Red Cedar likes neutral to slightly alkaline soil, roughly pH 6.5-7.5. If your soil or compost is acidic, a little garden lime or extra grit nudges it the right way — the one common plant where you may add lime.
Should I buy a bagged mix or make my own for western red cedar?
Bagged "herb" or "Mediterranean" mixes are usually fine for western red cedar, but most standard composts need cutting hard with grit. The DIY ratio above is cheap and exactly right.
How often should I refresh the soil for western red cedar?
A gritty mix barely breaks down, so western red cedar needs little repotting — refresh the top layer and the grit every couple of years rather than potting on aggressively. Sharp drainage is everything: a terracotta pot with a big hole, gritty mix and never a saucer left full. Raised beds suit these herbs outdoors for the same reason.
Keep reading
- Western Red Cedar care — the full brief (light, water, humidity, problems, pet safety)
- How often to water western red cedar — the schedule the mix feeds into
- Repotting western red cedar — when and how to refresh the mix
- Soil pH guide — test it and adjust it safely
- Overwatered plant — signs and recovery
- Root rot — how the wrong soil starts it, and how to save the plant
- Should I water my plant? The simple check first
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- All 6887 soil and potting-mix guides in the Growli library