Mature size & growth rate

How big does Blue Douglas Fir (Pseudotsuga menziesii var. glauca) get?

Also called Rocky Mountain Douglas Fir, Blue Rocky Mountain Fir, Interior Douglas Fir.

More about blue douglas fir

About Blue Douglas Fir

Pseudotsuga menziesii var. glauca · also called Rocky Mountain Douglas Fir, Blue Rocky Mountain Fir · flowering

Blue Douglas Fir is the cold-hardy inland variety of Douglas Fir, bearing blue-green to grey-green needles with a pleasant fragrance. More compact and cold-tolerant than the coastal variety, it forms a broadly pyramidal specimen tree with attractive pendulous cones. Not listed as toxic by the ASPCA; low-risk to pets.

Mature size: 15-30 m tall, 5-10 m wide at maturity; moderate growth rate of 30-60 cm per year

Indoor size vs how big it gets in the wild

Blue Douglas Fir is a tree at heart. Indoors a pot and your ceiling keep it to 15-30 m tall, 5-10 m wide at maturity, but in the ground it is a different scale of plant entirely (moderate growth rate of 30-60 cm per year). Indoors and in a pot, expect 15-30 m tall, 5-10 m wide at maturity. In the ground with no restriction it is a completely different plant — moderate growth rate of 30-60 cm per year — 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

Blue Douglas Fir is a moderate grower. Realistically, expect three to six years to reach mature indoor size, gaining a steady amount each growing season. Its feeding profile backs this up: apply a slow-release balanced conifer fertiliser in early spring during establishment. established trees in adequate soil rarely require supplemental feeding.

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

How to keep blue douglas fir smaller

You are not stuck with the maximum size. For blue douglas fir specifically, these are the levers, in order of impact:

The decisive tool is the secateurs: blue douglas fir 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 blue douglas fir 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 blue douglas fir bigger or faster

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

When blue douglas fir outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for blue douglas fir:

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 blue douglas fir repotting guide. If you want more of this plant instead of a bigger one, the blue douglas fir propagation guide turns prunings into new plants.

Blue Douglas Fir size — frequently asked questions

How big does blue douglas fir get?

Blue Douglas Fir reaches 15-30 m tall, 5-10 m wide at maturity when grown indoors, and far larger where it grows unrestricted (moderate growth rate of 30-60 cm per year). 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 blue douglas fir slow or fast growing?

Blue Douglas Fir is a moderate grower. Expect three to six years to reach mature indoor size, gaining a steady amount each growing season. Blue Douglas Fir is a tree at heart. Indoors a pot and your ceiling keep it to 15-30 m tall, 5-10 m wide at maturity, but in the ground it is a different scale of plant entirely (moderate growth rate of 30-60 cm per year).

How long does blue douglas fir take to reach full size?

Roughly three to six years to reach mature indoor size, gaining a steady amount each growing season. Light, pot size and feeding move that timeline more than anything else.

How do I keep blue douglas fir smaller?

The decisive tool is the secateurs: blue douglas fir 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 blue douglas fir 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.