Mature size & growth rate

How big does Holmstrup Arborvitae (Thuja occidentalis 'Holmstrup') get?

Also called Holmstrup Arborvitae, Columnar Thuja.

More about holmstrup arborvitae

About Holmstrup Arborvitae

Thuja occidentalis 'Holmstrup' · also called Holmstrup Arborvitae, Columnar Thuja · flowering

A slow, dense, narrowly columnar evergreen with rich green foliage in tight vertical sprays that hold colour well through winter. Its compact width and slow growth make it a low-maintenance choice for narrow screens, accents, and small-garden privacy. It prefers full sun and consistently moist, well-drained soil, and rarely needs pruning to keep its formal shape.

Mature size: About 3-4 m tall and 0.6-1.2 m wide over many years; slow and narrow.

Indoor size vs how big it gets in the wild

Holmstrup Arborvitae is a tree at heart. Indoors a pot and your ceiling keep it to about 3-4 m tall and 0.6-1.2 m wide over many years, but in the ground it is a different scale of plant entirely (slow and narrow.). Indoors and in a pot, expect about 3-4 m tall and 0.6-1.2 m wide over many years. In the ground with no restriction it is a completely different plant — slow and narrow. — 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

Holmstrup 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 helps young hedge plants; avoid late-season nitrogen that encourages frost-tender growth.

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

How to keep holmstrup arborvitae smaller

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

The decisive tool is the secateurs: holmstrup 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 holmstrup 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 holmstrup arborvitae bigger or faster

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

When holmstrup arborvitae outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for holmstrup 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 holmstrup arborvitae repotting guide. If you want more of this plant instead of a bigger one, the holmstrup arborvitae propagation guide turns prunings into new plants.

Holmstrup Arborvitae size — frequently asked questions

How big does holmstrup arborvitae get?

Holmstrup Arborvitae reaches about 3-4 m tall and 0.6-1.2 m wide over many years when grown indoors, and far larger where it grows unrestricted (slow and narrow.). 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 holmstrup arborvitae slow or fast growing?

Holmstrup 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. Holmstrup Arborvitae is a tree at heart. Indoors a pot and your ceiling keep it to about 3-4 m tall and 0.6-1.2 m wide over many years, but in the ground it is a different scale of plant entirely (slow and narrow.).

How long does holmstrup 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 holmstrup arborvitae smaller?

The decisive tool is the secateurs: holmstrup 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 holmstrup 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.