Mature size & growth rate

How big does Degroot's Spire Arborvitae (Thuja occidentalis 'Degroot's Spire') get?

Also called Degroot's Spire, Columnar Arborvitae.

More about degroot's spire arborvitae

About Degroot's Spire Arborvitae

Thuja occidentalis 'Degroot's Spire' · also called Degroot's Spire, Columnar Arborvitae · flowering

An exceptionally slim, spire-like evergreen with tightly twisted, dark green foliage sprays that give it distinctive texture. Its extremely narrow profile suits tight spaces, vertical accents, and slender screens where wider arborvitae won't fit. It prefers full sun and consistently moist, well-drained soil, holds its form without shearing, and is reliably cold-hardy.

Mature size: About 2.5-4 m tall and only 0.6-0.9 m wide; strikingly slim.

Indoor size vs how big it gets in the wild

Degroot's Spire Arborvitae is a tree at heart. Indoors a pot and your ceiling keep it to about 2.5-4 m tall and only 0.6-0.9 m wide, but in the ground it is a different scale of plant entirely (strikingly slim.). Indoors and in a pot, expect about 2.5-4 m tall and only 0.6-0.9 m wide. In the ground with no restriction it is a completely different plant — strikingly slim. — 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

Degroot's Spire Arborvitae is a slow grower. Realistically, expect a decade or more — slow growers like this add only a few centimetres a year, so expect 8-15+ years to reach their indoor ceiling. Its feeding profile backs this up: feed once in early spring with a balanced slow-release or evergreen fertiliser. a light second feed in early summer aids young plants; avoid late-season nitrogen that pushes frost-tender growth.

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

How to keep degroot's spire arborvitae smaller

You are not stuck with the maximum size. For degroot's spire arborvitae specifically, these are the levers, in order of impact:

The decisive tool is the secateurs: degroot's spire arborvitae 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.
Good news: slow growth means topping it once buys you years before it needs doing again.

The keep-it-smaller method, step by step

Pick the new height. Decide how tall you want degroot's spire arborvitae 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 degroot's spire arborvitae bigger or faster

If you want it to fill the space sooner, push the conditions rather than hoping — for degroot's spire arborvitae 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 degroot's spire arborvitae light requirements page covers exactly how bright a spot it needs to grow at its potential instead of stalling.

When degroot's spire arborvitae outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for degroot's spire arborvitae:

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 degroot's spire arborvitae repotting guide. If you want more of this plant instead of a bigger one, the degroot's spire arborvitae propagation guide turns prunings into new plants.

Degroot's Spire Arborvitae size — frequently asked questions

How big does degroot's spire arborvitae get?

Degroot's Spire Arborvitae reaches about 2.5-4 m tall and only 0.6-0.9 m wide when grown indoors, and far larger where it grows unrestricted (strikingly slim.). 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 degroot's spire arborvitae slow or fast growing?

Degroot's Spire Arborvitae is a slow grower. Expect a decade or more — slow growers like this add only a few centimetres a year, so expect 8-15+ years to reach their indoor ceiling. Degroot's Spire Arborvitae is a tree at heart. Indoors a pot and your ceiling keep it to about 2.5-4 m tall and only 0.6-0.9 m wide, but in the ground it is a different scale of plant entirely (strikingly slim.).

How long does degroot's spire arborvitae take to reach full size?

Roughly a decade or more — slow growers like this add only a few centimetres a year, so expect 8-15+ years to reach their indoor ceiling. Light, pot size and feeding move that timeline more than anything else.

How do I keep degroot's spire arborvitae smaller?

The decisive tool is the secateurs: degroot's spire arborvitae 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. Good news: slow growth means topping it once buys you years before it needs doing again.

How can I make degroot's spire arborvitae 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.