Pseudotsuga () is a genus of evergreen coniferous trees in the family Pinaceae (subfamily Laricoideae). Common names for species in the genus include Douglas fir, Douglas-fir, Douglas tree, Oregon pine and Bigcone spruce. Pseudotsuga menziesii (Douglas fir proper) is widespread in western North America and is an important source of timber. The number of species has long been debated, but two in western North America and two to four in eastern Asia are commonly acknowledged.

Nineteenth-century botanists had problems in classifying Douglas firs, due to the species' similarity to various other conifers better known at the time; they have at times been classified in Pinus, Picea, Abies, Tsuga, and even Sequoia. Because of their distinctive cones, Douglas firs were finally placed in the new genus Pseudotsuga (meaning "false hemlock") by the French botanist Carrière in 1867.

Name

The tree takes its English name from David Douglas, the Scottish botanist who introduced Pseudotsuga menziesii into cultivation at Scone Palace in 1827. Douglas is known for introducing many native American tree species to Europe. The hyphenated form "Douglas-fir" is used by some to indicate that Pseudotsuga species are not true firs, which belong to the genus Abies.

Description

Douglas-firs are medium-size to extremely large evergreen trees, tall (although only coast Douglas-firs reach such great height). The leaves are flat, soft, linear, long, generally resembling those of the firs, occurring singly rather than in fascicles; they completely encircle the branches, which can be useful in recognizing the species. The female cones are pendulous, with persistent scales (unlike true firs), and are distinctive in having a long tridentine (three-pointed) bract that protrudes prominently above each scale (it resembles the back half of a mouse, with two feet and a tail).

Pseudotsuga menziesii var. menziesii has attained heights of 393 feet (120* m). That was the estimated height of the tallest conifer ever well-documented, the Mineral Tree (Mineral, Washington), measured in 1924 by Dr. Richard E. McArdle, former chief of the U.S. Forest Service. The volume of that tree was . The tallest living individual is the Brummitt (Doerner) Fir in Coos County, Oregon, tall. Only coast redwood and Eucalyptus regnans reach greater heights based on current knowledge of living trees: 379 and 331 feet (116 and 101* m), respectively.

At Quinault, Washington, is found a collection of the largest Douglas-firs in one area. Quinault Rain Forest hosts most of the top ten known largest Douglas-firs.

, the largest known Douglas-firs in the world were, by volume:

  1. Red Creek Tree (Red Creek, SW British Columbia)
  2. Queets Fir (Queets River Valley-Olympic National Park)
  3. Tichipawa (Quinault Lake Rain Forest-Olympic National Park)
  4. Rex (Quinault Lake Rain Forest-Olympic National Park)
  5. Ol' Jed (Jedediah Smith Redwoods State Park)

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File:Douglas Fir branch-750px.JPG|Coast Douglas-fir branch

File:Pseudotsuga 01.jpg |Rocky Mountain Douglas-fir twig

File:Pseudotsuga menziesii cone.jpg|Coast Douglas-fir seed cone, from a tree grown from seed collected by David Douglas

File:Pinetum woburnense- or, a catalogue of coniferous plants, in the collection of the Duke of Bedford, at Woburn Abbey; systematically arranged - DPLA - 8a670d36bcbdfca27225d24ef65871ed (page 185).jpg|Botanical illustration

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Taxonomy

Phylogeny of Pseudotsuga according to Stull 2021:

By far the best-known is the widespread and abundant North American species Pseudotsuga menziesii, a taxonomically complex species divided into two major varieties (treated as distinct species or subspecies by some botanists): coast Douglas-fir or "green Douglas-fir", on the Pacific coast; and Rocky Mountain Douglas-fir or "interior Douglas-fir", in the interior west of the continent. According to some botanists, Rocky Mountain Douglas-fir extends south into Mexico to include all Mexican Douglas-fir populations, whereas others have proposed multiple separate species in Mexico and multiple varieties in the United States. Morphological and genetic evidence suggest that Mexican Douglas-fir should probably be considered a distinct variety within P. menziesii.

All of the other species are of restricted range and little-known outside of their respective native environments, where they are often rare and of scattered occurrence in mixed forests; all those have unfavorable conservation status. The taxonomy of the Asian Douglas-firs continues to be disputed, but the most recent taxonomic treatment accepts four species: three Chinese and one Japanese. or broken down into additional species and varieties. In the current treatment, the Chinese species P. sinensis is further subdivided into two varieties: var. sinensis and var. wilsoniana.

North America

  • Pseudotsuga macrocarpa <small>(Vasey) Mayr</small> bigcone Douglas-fir – southern California
  • Pseudotsuga menziesii <small>(Mirb.) Franco</small> – western North America from Alaska to Oaxaca
  • Pseudotsuga menziesii var. menziesii coast Douglas-fir
  • Pseudotsuga menziesii var. glauca <small>(Beissn.) Franco</small> Rocky Mountain Douglas-fir
  • Pseudotsuga menziesii var. lindleyana <small>(Roezl) Carrière</small> Mexican Douglas-fir

Asia

  • Pseudotsuga brevifolia <small>W.C.Cheng & L.K.Fu</small> short-leaf Chinese Douglas-fir
  • Pseudotsuga forrestii <small>Craib</small> Yunnan Douglas-fir
  • Pseudotsuga japonica <small>(Shiras.) Beissn.</small> Japanese Douglas-fir
  • Pseudotsuga sinensis <small>Dode</small> Chinese Douglas-fir
  • Pseudotsuga sinensis var. sinensis
  • Pseudotsuga sinensis var. wilsoniana Taiwan Douglas-fir
  • Pseudotsuga sinensis var. gaussenii

Pests and diseases

Douglas-firs are used as food plants by the larvae of some Lepidoptera species, including autumnal moth, bordered white, engrailed moth, pine beauty and turnip moth. The gelechiids Chionodes abella and Chionodes periculella and the tortrix moth Cydia illutana have been specifically recorded on P. menziesii.

Culture

A California Native American myth explains that each three-ended bract is the tail and two tiny legs of a mouse that hid inside the scales of the tree's cones during forest fires, and the tree was kind enough to be its enduring sanctuary.

A Douglas-fir species, Pseudotsuga menziesii, is the state tree of Oregon.

References

  • Gymnosperm Database – Pseudotsuga
  • Arboretum de Villardebelle: Images of Pseudotsuga species cones