Pseudotsuga menziesii Seeds | Douglas Fir
LATIN NAME: Pseudotsuga menziesii
COMMON NAME: Douglas Fir
Plant Profile
The bract is the most reliable field character in the genus Pseudotsuga. In Abies the bracts sit hidden behind the scales or vanish inside the cone; here they are stiff, long-exserted and tridentate. Seed sits in pairs at the base of each scale, winged for wind, and the cone carries it away from the parent on the first dry autumn gale.
True firs hold their cones upright and the cones disintegrate on the tree, shedding scales and leaving a bare spike. Douglas fir cones hang down and fall whole, which is why intact cones litter the ground beneath a good tree. The needles are soft and flat, arranged all round the twig rather than combed to two sides, with two pale stomatal bands beneath.
Two varieties cover an enormous span of climate. The coastal form, var. menziesii, occupies the fog belt from British Columbia to northern California, where it is among the tallest trees on earth, with thick corky bark and a fast, straight trunk. The interior form, var. glauca, holds the Rocky Mountains and the dry interior plateaus; it is shorter, hardier, and its needles carry a heavier load of stomatal wax that turns the foliage distinctly blue.
Archibald Menzies collected the first specimens on the Pacific coast in the 1790s, which is why the species epithet honours him, but it was David Douglas who sent seed back to Britain in the 1820s and fixed the tree in European gardens and in its common name. Pseudotsuga means false hemlock, because the foliage had been mistaken for a hemlock before anyone had a cone to examine.
The fungus Phaeocryptopus gaeumannii causes Swiss needle cast, plugging the stomata of the needles so that a tree loses its older foliage year on year and thins from the inside. It is worst in the mild, damp coastal fog belt, and it is the main health problem of plantation Douglas fir in western Oregon and Washington.
Science & Biotechnology
Douglas fir is one of the conifers in which somatic embryogenesis is routine laboratory practice: immature zygotic embryos are cultured to give embryogenic cell lines, the lines are multiplied, and mature somatic embryos are raised into plantlets. The lines can be cryopreserved in liquid nitrogen and revived years later, which underpins clonal forestry programmes that keep a selected genotype frozen while its performance is field-tested.
Uses & Benefits
Resin canals run through the bark and the needles and carry a turpentine in which beta-pinene is the leading monoterpene, with sabinene, camphene and limonene among the minors. Steam distillation of the needles gives an oil with a balsamic, faintly citrus note used in room sprays rather than in perfumery. The hardened pitch was chewed as a gum by the peoples of the Pacific Northwest and was used to waterproof baskets and canoes.
The timber is one of the great structural softwoods. It is stiff and strong for its weight, which puts it into laminated beams, plywood and marine piling, and old-growth wood is dense enough to be graded for load-bearing work. The same tree carries a second trade: it is a leading Christmas conifer in North America and Britain, sold as cut trees and as greenery for wreaths, and it holds its needles well if the butt is kept in water.
Growing from Seed
The seed needs a cold, moist period before sowing, though it stores well dry and cold. Mix it with damp sand or vermiculite, keep it cool and damp for a while, then sow five to ten millimetres deep in a free-draining mix of two parts peat-free compost, one part coarse grit and a little bark. The species makes a deep taproot and resents disturbance, so deep containers beat cell trays. Keep young seedlings in light shade through their first summer.
Move seedlings on when they stand about fifteen to twenty centimetres tall and the stems have begun to stiffen, since commercial growers lift bare-root stock by height and caliper rather than by the calendar. Plant out at two to three metres, water deeply for two summers and then stop, because a coddled tree makes the thin, floppy growth that never straightens. Rabbits and voles strip bark from young stems in winter.
Our Take
For sheer speed from a packet, this is the conifer I would plant first, and I would plant it where the roots have room, because a happy tree is not a small one. Noble fir is the true fir that fills the same Christmas slot and holds its needles even better, the Chinese Douglas fir is its smaller Asian cousin for a tighter garden, and blue spruce gives the blue-grey colour of the interior form in a much slower, more compact tree. Sow in damp sand, wait for the cold to pass, and do not fuss over the seedlings.
Related Reading
Gardeners who grow Douglas Fir often pair it with these related subjects: