Rocky Mountain Douglas Fir Plant Care

Rocky Mountain Douglas Fir (Pseudotsuga menziesii var. glauca) belongs to the Pinaceae family within the Pseudotsuga genus. Rocky Mountain Douglas Fir is native to the interior mountainous regions of western North America, from central British Columbia and southwest Alberta in Canada southward through the United States to the far north of Mexico. Rocky Mountain Douglas Fir is also known as Blue Douglas Fir.

Rocky Mountain Douglas Fir displays a tall, conical tree growth habit, reaching up to 100 ft tall with a spread of approximately 20 ft. Rocky Mountain Douglas Fir produces small, inconspicuous cones.

Leaf size: approximately 2 inches.

Water a young or newly planted Rocky Mountain Douglas Fir every 14–21 days, soaking the whole root zone, until it is established — usually one to two growing seasons. Established trees mainly need water during long dry spells. In a container, water whenever the top few centimetres of soil are dry.

Rocky Mountain Douglas Fir thrives in full sun to partial shade.

Pseudotsuga menziesii var. glauca tolerates temperatures of 0–90°F. Rocky Mountain Douglas Fir prefers humidity levels of 40–70%.

Well-draining, acidic soil with good aeration. Good drainage is essential for Rocky Mountain Douglas Fir to prevent waterlogging, which leads to root rot and fungal issues.

Choose a spot with full sun to partial shade and well-draining, acidic soil with good aeration. Avoid low spots where water collects after rain.

Plant container-grown or balled-and-burlapped trees in spring or early autumn, setting the root flare at soil level, and water well after planting.

Rocky Mountain Douglas Fir can spread to about 20 ft (6.1 m) and reach about 100 ft (30 m) tall. Space plants about 20 ft (6.1 m) apart so mature crowns don't crowd each other, and plant at least half that distance from buildings, fences and paths.

Planning a row or hedge? Try the tree spacing calculator.

Rocky Mountain Douglas Fir needs little pruning. Remove dead, damaged or crossing branches in late winter or early spring.

Don't cut back into old, bare wood: conifers in the pine family rarely sprout new growth from it. To keep a denser shape, trim only the soft new shoots in late spring.

Water deeply in late autumn before the ground freezes — evergreens keep losing water through their needles all winter, and spread a 5–8 cm (2–3 in) layer of mulch over the root zone, keeping it away from the trunk.

Young and container-grown trees need extra protection: roots in a pot freeze much more easily than roots in the ground.

A cut Rocky Mountain Douglas Fir stays fresh much longer when it can keep drinking. These steps apply to any cut fir, spruce, Douglas fir or pine.

1. 1. Make a fresh cut

   Saw about 2–3 cm (1 in) off the base of the trunk just before you put the tree in its stand. An old cut seals over with sap within hours and the tree can no longer take up water.

2. 2. Water the stand daily

   Use a stand that holds plenty of water — a common rule of thumb is about 1 litre per 2.5 cm (1 quart per inch) of trunk diameter. Check it every day and never let the level drop below the cut end; a fresh tree drinks the most in its first week. Plain water is enough.

3. 3. Keep it away from heat

   Set the tree well away from fireplaces, radiators, heating vents and sunny windows, which dry the needles quickly. Use low-heat LED lights and switch them off at night and when you leave the house.

4. 4. Take it down when it dries out

   If needles snap instead of bending, or fall in showers when you brush a branch, the tree has dried out and is a fire risk — remove it.

Pets: Rocky Mountain Douglas Fir is reported as toxic to pets in our plant data (not verified by the ASPCA), so treat it with caution. If your pet ate a plant, contact your vet or animal poison control.

Rocky Mountain Douglas Fir can be propagated through seeds, grafting. Similar propagation techniques also apply to douglas fir plant care, which shares the same genus.

See all plants toxic to cats and plants toxic to dogs.

Rocky Mountain Douglas Fir is susceptible to aphids, spider mites, spruce budworm. Inspect the foliage regularly, especially along leaf undersides and stems. Treat infestations promptly with insecticidal soap or neem oil to prevent spread.

Yellow leaves, brown tips or drooping? See common plant problems and how to fix them.