The Douglas fir is not a true fir tree. The genus name (Pseudotsuga) suggests that this is similar to hemlock trees. Pseudo- means false, and Tsuga is the genus for hemlocks. The species is menziesii. This tree is one of many conifers included in the Pinaceae family. Others are cedars, the deciduous conifers (Glyptostrobus, Larix, Metasequoia, Pseudolarix, and Taxodium), fir trees, pine trees, and spruce trees. The Douglas fir is monoecious and both male and female strobili are produced on the tree. The red-brown cones are long and have distinct bracts that come out between the scales.
Light
The Douglas fir must have full sun wherever you plant it. It can tolerate partial sun, but it prefers full sun.
Soil
The ideal soil for this tree is an acidic loam that drains. You can work on making your soil more acidic. It should be moist and well-draining.
Temperature and Humidity
If you live in zones 4 to 6, this could be the evergreen tree for you.
Water
Don’t plant this evergreen in an area where there is drought. It requires moist soil, which could mean supplemental watering from you.
Pruning
Douglas firs should have one strong central leader growing upright. If you have a young tree with two stems, pick the stronger of the two and cut the weaker one. Trees with co-dominant stems, particularly conifers, can be dangerous once mature. For aesthetics, Douglas fir is best left alone as far as pruning goes unless it needs to be trimmed for damaged, diseased, or dead branches.
Types of Douglas Fir
Pseudotsuga menziesii var. menziesii is the coast Douglas firPseudotsuga menziesii var. glauca may be called either the interior Douglas fir or the Rocky Mountain Douglas fir
Common Pests and Plant Diseases
There are quite a few pests and diseases that may potentially affect your Douglas fir, but you usually shouldn’t have major problems. They include: Pests
Black pine leaf scale (Nuculaspis californica) Black vine weevil (Otiorhynchus sulcatus) Conifer twig weevil (Pissodes spp.) Cooley spruce gall adelgid (Adelges cooleyi) Douglas-fir bark beetle (Dendroctonus pseudotsugae) Douglas-fir bud mite (Trisetacus pseudotsugae) Douglas-fir cone gall midge (Contarinia oregonensis) Douglas-fir cone moth (Barbara colfaxìana) Douglas-fir dwarf mistletoe (Arceuthobium do) Douglas-fir pitch moth (Synanthedon novaroensis) Douglas-fir seed chalcid (Megastigmus spermotrophus) Douglas-fir tussock moth (Orgyia pseudotsugata) Douglas-fir twig weevil (Cylindrocopturus furnissi) Elongate hemlock scale (Fiorinia externa) Fall webworm (Hyphantria cunea) Fir coneworm (Dioryctria abietìvorella) Giant conifer aphid (Cinara spp.) Monterey pine aphid (Essigella californica) Pine needle scale (Chionaspis pinifoliae) Silver-spotted tiger moth (Halsidota argentata) Spruce aphid (Elatobium abietina) Spruce gall adelgid (Adelges abietis and Adelges cooleyi) Spruce spider mite (Oligonychus ununguis) Western pine spittlebug (Aphrophora fulva) Western spruce budworm (Choristoneura fumiferana)
Diseases
Heart rot fungi Laminated root rot (Phellinus weirii) Needlecast (Rhabdocline pseudotsugae) Red ring rot (Phellinus pini) Shoestring root rot (Armillaria mellea)
