Mature size & growth rate

How big does Western Red Cedar (Thuja plicata) get?

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.

Mature size: 30–70 m tall in the wild; 15–30 m in gardens; up to 6–8 m wide; fast-growing (30–60 cm per year in good conditions)

Indoor size vs how big it gets in the wild

Western Red Cedar is a tree at heart. Indoors a pot and your ceiling keep it to 30–70 m tall in the wild, but in the ground it is a different scale of plant entirely (15–30 m in gardens; up to 6–8 m wide; fast-growing (30–60 cm per year in good conditions)). Indoors and in a pot, expect 30–70 m tall in the wild. In the ground with no restriction it is a completely different plant — 15–30 m in gardens; up to 6–8 m wide; fast-growing (30–60 cm per year in good conditions) — which is why the pot, the light and the pruning matter so much for the size you actually end up with.

It gains real height on a trunk or main stem, adding a tier of leaves a year and eventually reaching for the ceiling — this is a plant you grow up, not out.

Growth rate and years to mature

Western Red Cedar is a fast grower. Realistically, expect two to four years from a young plant to a room-filling specimen in good light. Its feeding profile backs this up: not required in fertile garden soils. on poor soils, apply a balanced slow-release conifer fertiliser in early spring. established trees do not benefit from heavy feeding; excess nitrogen promotes soft growth more susceptible to aphids and didymascella leaf blight.

Want this turned into the right next pot at the right moment? The pot size calculator and the western red cedar repotting guide cover when and how much to size up — pot size is one of the biggest levers on how fast western red cedar grows.

How to keep western red cedar smaller

You are not stuck with the maximum size. For western red cedar specifically, these are the levers, in order of impact:

The decisive tool is the secateurs: western red cedar can be topped (cut the main growing tip) to cap its height and force a bushier, shorter shape.
Keeping it deliberately pot-bound in a snug container slows the whole plant and limits ultimate size.
Prune in spring so it heals fast; remove the tallest leader back to a node to reset the height.
Expect to top or hard-prune it every year or two — left alone it heads for the ceiling.

The keep-it-smaller method, step by step

Pick the new height. Decide how tall you want western red cedar and find a leaf node or branch point just below that.
Top the main stem. Cut the main growing tip cleanly just above that node in spring; this permanently caps the height and forces side branches.
Keep the pot snug. Avoid jumping to a much bigger pot — a slightly restricted rootball keeps the whole plant smaller.
Maintain the shape. Prune back the tallest new leaders each spring to hold it at the height you chose.

How to grow western red cedar bigger or faster

If you want it to fill the space sooner, push the conditions rather than hoping — for western red cedar the accelerators are:

It already wants the bright light it needs; warmth, a yearly pot-up and spring-summer feed are the accelerators.
Pot up a size every year or two while young; restricted roots are the main thing holding height back.
Feed regularly through the growing season and keep it warm — height comes from sustained good conditions.

Light is almost always the ceiling. The western red cedar light requirements page covers exactly how bright a spot it needs to grow at its potential instead of stalling.

When western red cedar outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for western red cedar:

The top leaves pressing against or bent by the ceiling — the classic "this is now too tall indoors" sign.
It has to be moved away from a light source it has literally outgrown.
Roots filling the largest pot you can reasonably keep indoors — at that point it is top-or-prune or move it outside (if hardy).

If it is the pot rather than the room, it is a repotting job, not a goodbye — see the western red cedar repotting guide. If you want more of this plant instead of a bigger one, the western red cedar propagation guide turns prunings into new plants.

Western Red Cedar size — frequently asked questions

How big does western red cedar get?

Western Red Cedar reaches 30–70 m tall in the wild when grown indoors, and far larger where it grows unrestricted (15–30 m in gardens; up to 6–8 m wide; fast-growing (30–60 cm per year in good conditions)). It gains real height on a trunk or main stem, adding a tier of leaves a year and eventually reaching for the ceiling — this is a plant you grow up, not out.

Is western red cedar slow or fast growing?

Western Red Cedar is a fast grower. Expect two to four years from a young plant to a room-filling specimen in good light. Western Red Cedar is a tree at heart. Indoors a pot and your ceiling keep it to 30–70 m tall in the wild, but in the ground it is a different scale of plant entirely (15–30 m in gardens; up to 6–8 m wide; fast-growing (30–60 cm per year in good conditions)).

How long does western red cedar take to reach full size?

Roughly two to four years from a young plant to a room-filling specimen in good light. Light, pot size and feeding move that timeline more than anything else.

How do I keep western red cedar smaller?

The decisive tool is the secateurs: western red cedar can be topped (cut the main growing tip) to cap its height and force a bushier, shorter shape. Keeping it deliberately pot-bound in a snug container slows the whole plant and limits ultimate size. Prune in spring so it heals fast; remove the tallest leader back to a node to reset the height. Expect to top or hard-prune it every year or two — left alone it heads for the ceiling.

How can I make western red cedar grow bigger or faster?

It already wants the bright light it needs; warmth, a yearly pot-up and spring-summer feed are the accelerators. Pot up a size every year or two while young; restricted roots are the main thing holding height back. Feed regularly through the growing season and keep it warm — height comes from sustained good conditions.