A tree up to 200 ft high in the wild, with a trunk sometimes 15 ft in diameter at the buttressed base; in cultivation a slender, pyramidal tree in some places already approaching 100 ft in height. Unless close-planted it retains its branches to the ground, but is inclined to become thin at the top. Branches curving upwards at the ends, branchlets drooping, strong-smelling and slightly aromatic when crushed; ultimate subdivisions 1⁄16 to 1⁄12 in. wide, flattened. Leaves dark glossy green, scale-like, 1⁄12 to 1⁄8 in. long; the lateral ones the longer, with their edges infolded and overlapping the flatter ones above and below the twig; they are all sharply pointed and have glaucous patches beneath. Cones egg-shaped, 1⁄2 in. long; scales about ten, with a small triangular boss just beneath the apex.
Native of the coastal ranges of western N. America from S.E. Alaska to northernmost California, and with a second area in the northwestern Rocky Mountains. It was discovered at the end of the 18th century during the Malaspina expedition and was described by David Don in Lambert’s The Genus Pinus from a specimen collected by Taddaeus Haenkel, assistant to Née, chief botanist to the expedition, on Nootka Sound (Née himself is usually credited with the discovery though he in fact remained in Mexico while the expedition explored northwards). It was introduced by Thomas Lobb in 1853 (possibly two years earlier to Scotland by John Jeffrey, for the Oregon Association), and the horticultural name T. lobbii has clung to it ever since.
T. plicata is distinguished from the E. American T. occidentalis by the glaucousness of the underside of the branchlet, the absence or obscurity of gland-pits on the upper surface of the leaves, and its much more rapid, cleaner growth. From T. standishii it differs in its denser habit, finer spray, and different odour.
Although not strong, the timber of the western thuya is easily worked, remarkably light, does not warp, and is remarkably resistant to decay. Imported into Britain, western red cedar is much used for garden buildings, outdoor furniture, cladding, etc., and in its native country for making roof shingles. It is also the wood from which most pencils are made.
In Britain T. plicata has proved by far the handsomest and best growing of the thuyas. Although commonest as a specimen tree, it is also useful for hedges and shelter belts and has been planted to some extent as a forest tree. In its native forests the western red cedar attains maturity at an age of about 100 years, but home-grown timber from stands half that age is of good quality and is used mainly for fencing, gates and ladder poles. The principal drawback of this species is that seedlings are often attacked by the fungus Didymascella (Keithia) thujina.
T. plicata grows well over much of the country, on all except very dry soils, but the best specimens are in the Atlantic zone, as is usually the case with the conifers of the American Pacific region. The most remarkable English specimens are: Stourhead, Wilts, behind the Lake, pl. c. 1854, 115 × 161⁄4 ft (1976), by the entrance, 105 × 141⁄4 ft (1976); Fonthill, Wilts, from 1860 seed, 120 × 15 ft (1963) and 115 × 14 ft (1976); Bicton, Devon, 128 × 141⁄4 ft (1968) and 120 × 15 ft (1963); Rhinefield Drive, New Forest, pl. 1861, 132 × 12 ft (1976); and, to indicate growth outside the optimum area, National Pinetum, Bedgebury, Kent, pl. 1916, 63 × 51⁄4 ft (1970).
Among the largest examples in Scotland are: Strone, Argyll, pl. 1875, 129 × 161⁄4 ft (1976); Inveraray, Argyll, Lime Kilns, 117 × 151⁄4 ft (1969); Belladrum, Inverness-shire, 115 × 161⁄4 ft (1970).
T. plicata has given rise to fewer cultivars than T. occidentalis:
cv. ‘Atrovirens’. – Foliage dark green and glossy, in broad sprays. Smith of Worcester, 1874.
cv. ‘Excelsa’. – A fast growing, columnar tree with short horizontal branches and dark green glossy foliage. Put into commerce by J. Timm and Co. of Elmshorn, Germany. It is an excellent hedging plant.
cv. ‘Fastigiata’. – Branches steeply ascending; foliage dense. As a hedging plant it needs less clipping than the normal form and also makes a good specimen (T. menziesii fastigiata Carr.; T. plicata var. pyramidalis Bean).
cv. ‘Gracilis’. – Sprays finer and with smaller leaves. Rare in cultivation and of no value.
cv. ‘Hillieri’. – A slow-growing bush with stout, crowded branches and branchlets, the leaf-sprays borne in irregular whorls. Eventually 8 or 10 ft high. ‘A very irregular bush, with foliage so dense that one wonders how light or moisture can ever penetrate its centre.’ (Hornibrook). Raised by Messrs Hillier about 1900.
cv. ‘Rogersii’ (‘Rogersii Aurea’). – A dwarf, very slow-growing golden bush of ellipsoid or broadly conical habit, densely foliaged. Raised by George Gardiner for Messrs Rogers about 1914 but not described until 1929, when the mother plant was only 23⁄4 ft high (Gard. Chron., Vol. 85 (1929), p. 50; ibid., Vol. 149 (1961), p. 502).
Another of Mr Gardiner’s raising is ‘Stoneham Gold’, put into commerce by Messrs Rogers in 1948 but raised much earlier. It is more vigorous and less dense, the older leaves dark green, the younger bright gold. Both were raised from a tree grown under the name T. plicata aurea.
cv. ‘Zebrina’. – Spray with curious patches of yellow interspersed with the ordinary green of the current year’s shoots. It is a more attractive conifer than this description would suggest, the tree being shapely and dense, and from a short distance appearing golden-green – a colour that is constant throughout the year. Its origin is uncertain, but it is probably a renaming of one of several clones cultivated in the last century as T. gigantea aureovariegata. A tree under the present name was introduced to Kew about 1900. The oldest dated examples were planted soon after that and are now 60 to 70 ft or slightly more high (measured 1968-76). Trees of this size grow at Bicton, Devon; Stourhead, Wilts; Nymans and Tilgate, Sussex; Grayswood Church, near Haslemere, Surrey; Hardwicke, Suffolk.
cv. ‘Semperaurescens’. – Leaves yellowish green. Rare. There is an example at Westonbirt, Glos.