Pseudotsuga

( soo - doh - SOO - guh )

At-A-Glance Information

This genus of evergreen trees includes species which thrive in full sun and need little or no water once mature. These conifers are native to western North America and eastern Asia. There are many garden forms of this genus that have been developed, commonly called Douglas Fir, Douglas-Fir, Douglas Tree, Oregon Pine, and Bigcone Spruce. Foliage is typically shades of true green to deep green. Use these landscape trees as background foliage, as large shade trees, or as specimens in the garden.

pseudotsuga Species and Varietals

The genus Pseudotsuga is a member of the plant family Pinaceae and includes 6 species. Trees in this genus are closely related to those in Larix (Larch), Pinus (Pine), Cathaya, and Picea (Spruce). The best growing zones for Pseudotsuga trees vary depending on the species grown. For more information, read the descriptions below. To find your zone, click here: Zone Map.

Pseudotsuga japonica (Japanese Douglas Fir, Togasawara, トガサワラ, Goyo-toga, Sawara-toga)
This species grows well in USDA hardiness zones 7 and 8 or Sunset growing zones 3b-9 and 14-17 and is native to southern Japan. In gardens, these trees reach 45 feet tall with a somewhat conical form. Bark is grey, needles are grey, and cones are purple-brown (and about 3 inches long).

Pseudotsuga macrocarpa (Bigcone Spruce, Bigcone Douglas Fir)
This species is best in USDA hardiness zones 7-9 or Sunset growing zones 3-11 and 14-23; it is native to southern California mountain ranges. These trees have stout trunks and top out around 60 feet tall with canopies spreading to 30 feet wide. This species is relatively drought-tolerant and has large cones.

Pseudotsuga menziesii (Douglas Fir)
This species grows well in USDA hardiness zones 4-6 or Sunset growing zones A2, A3, 1-10 and 14-17. Trees reach 80 to 160 feet tall and 20 to 30 feet wide in gardens. Young trees are widely sold as holiday trees. Needles are soft and deep green to bluish-green, branches are turned up. Cones will attract butterflies. Cultivars include 'Graceful Grace' (upright weeping tree with long blue needles to 20-30 feet tall), 'Idaho Gem' (miniature globose shrub to 12 inches tall), 'Vail' (dwarf, irregularly shaped or conical with blue-green foliage), 'Fastigiata' (upright columnar form), and 'Pendula' (weeping form with twisted, cascading green stems). This species is resistant to Oak Root Fungus. This species is considered invasive in Argentina, New Zealand, Chile, Great Britain, Germany, Austria, California and the Pacific Northwestern United States.

Pseudotsuga sinensis (Chinese Douglas, Chinese Douglas-Fir, Yellow Fir, Huáng Shān, 黄杉)
Best in USDA hardiness zones 7 to 9 or Sunset growing zones 4-9 and 14-17, this species is native to China and Taiwan. Trees reach up to 50 feet tall and 25 feet wide at the base. They grow much taller in their natural habitat. All trees have an open habit and good-looking silhouette. Varieties include Pseudotsuga sinensis sinensis (also called Pseudotsuga sinensis gaussenii, or Gaussen's Douglas Fir; chartreuse cones that mature to brown) and Pseudotsuga forrestii (with longer needles than the species and 3 inch-long cones).

Caring for pseudotsuga

Pseudotsuga trees need some space in the landscape to grow; as specimens or full-size landscape trees, they should be spaced 20 to 30 feet apart. For smaller gardens, they can be given 15 feet of space, and should also be planted at least 15 feet from homes and other buildings. If growing Pseudotsuga as a privacy screening plant, install them 8 to 10 feet apart. They should be planted in a spot in the landscape that receives bright, direct sunlight for between 6 and 8 hours of the day. They will grow the fastest and produce lush foliage in this exposure. The best time to plant these trees is in spring or early fall. Young trees should be sheltered from strong, drying winds which can injure new growth. Ensure that soil is well-draining before installing trees; if local soils are particularly poor or clayey, the planting site will need to be amended with plenty of organic material and/or sand. Apply a thick layer of mulch around plantings to increase soil moisture retention, suppress weed growth, and regulate soil temperatures.

Newly planted and young trees require regular waterings; established trees are considered to be drought tolerant, getting by on precipitation alone during the wet months of the year. During the warmer months, deep water trees when soil is almost completely dry. These trees are very sensitive to having wet feet, so make sure that standing water is not present around the root zone. Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. Prune trees in late wintertime to early springtime when they are dormant, removing dead, damaged, diseased, or crossing branches. These trees can also be lightly shaped at this time, though this step is not necessary as they typically form a very handsome shape on their own. Pseudotsuga trees have a lifespan of between 500 and 1,000 years or more in their native landscapes. In gardens, their life span is shortened to between 50 to 100 years.

Propagation

Pseudotsuga can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Pseudotsuga, follow the instructions below:

Propagating Pseudotsuga by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. A good substrate for propagation of cuttings is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.

Propagating Pseudotsuga by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Harvest your seeds. The cones on Pseudotsuga plants are pretty easy to spot, they're quite large and attach to branches, left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cones will typically begin to fall from the trees in August and September. They can also be cut off of the plant and placed in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will begin to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 7-14 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.

Pseudotsuga cones contain between 25 and 50 seeds each. Two seeds develop on each scale.

Pseudotsuga seeds are wedge-shaped, dark brown, and have a single attached wing.

Problems and Pests

Certain Pseudotsuga species are considered invasive in some regions; see the species descriptions above for more information. Check with local authorities before planting. Although Douglas Fir trees are typically pest and disease-free, they can suffer from the following from time to time: