IUCN threat status:

Least Concern (LC)

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Cupressus nootkatensis

Cupressus nootkatensis D.Don (Nootka Cypress; syn. Callitropsis nootkatensis (D.Don) Florin, Xanthocyparis nootkatensis (D.Don) Farjon & Harder, Chamaecyparis nootkatensis (D.Don) Spach), is a cypress (Cupressaceae) species native to western North America.

Taxonomy
It has a complex taxonomic and nomenclatural history. It was first described in the genus Cupressus as Cupressus nootkatensis by David Don in 1824, but in 1841 it was transferred to Chamaecyparis by Édouard Spach on the basis of its foliage being in flattened sprays (as in other Chamaecyparis, but unlike most, though not all, other Cupressus species). This treatment was almost universally used through the 20th century. However, this does not fit with the morphology and phenology of the cones, which are far more like Cupressus, like them maturing in their second year, not in their first (Frankis 1993) and it can also be grafted onto rootstocks of other Cupressus but not onto other Chamaecyparis (Welch 1991). Subsequent genetic (Gadek et al. 2000) and micromorphological (Jägel & Stützel 2001) evidence also strongly supported its return to Cupressus and exclusion from Chamaecyparis.

More recently, Farjon et al. (2002) transferred it to a new genus Xanthocyparis, together with the newly discovered Xanthocyparis vietnamensis (Cupressus vietnamensis); this species is similar to Nootka Cypress in many ways, in that while they are not related to Chamaecyparis, they differ from other Cupressus in usually having just four cone scales, not six or more as usual in other Cupressus. Little et al. (2004, 2006) pointed out that an earlier nomenclatural combination in the genus Callitropsis existed, as Callitropsis nootkatensis (D.Don) Oerst., published in 1864 but overlooked by other subsequent authors. Little et al. therefore synonymised Xanthocyparis with Callitropsis, the correct name for these species under the ICBN when treated in a distinct genus. Little further pointed out that the other species of Cupressus native to North America are more closely related to Nootka Cypress than they are to Cupressus sempervirens (the type species of Cupressus) and other Old World Cupressus species. He therefore transferred all of the American Cupressus species to Callitropsis.

However, other botanists (Xiang & Li 2005, Rushforth 2007) pointed out that the separation of Callitropsis (or Xanthocyparis) from Cupressus is uncertain on this evidence, and that the species of Callitropsis are best retained in Cupressus unless further genetic evidence for splitting Cupressus could be found. This has now been confirmed by DNA studies by Mu et al. (2006), which placed Nootka Cypress in the middle of several Chinese Cupressus, closest to Cupressus funebris and Cupressus duclouxiana, and by Mao et al. (2010), which placed it within Cupressus as sister to all the American Cupressus species. The cones having just four scales is also not conclusive, with several other Cupressus species (C. bakeri, C. glabra, C. lusitanica) occasionally having four-scaled cones. Treatment in Cupressus is accepted and recommended by the Cupressus Conservation Project and the Gymnosperm Database.

Morphology
Nootka Cypress is an evergreen tree to 40 m tall and a trunk up to 1 m diameter (exceptionally to 60 m tall and 4 m diameter), with stringy grey-brown to purple-brown bark. The crown is conic-columnar, with horizontal or pendulous branches, and more strictly pendulous branchlets. The foliage is in flat sprays, with dark green scale-leaves 3-5 mm long; when crushed, they have a strong sour-resinous odour. The seed cones have four (occasionally six) scales, most closely resembling the cones of Cupressus lusitanica, except being somewhat smaller, typically 10-14 mm diameter. Each scale has a pointed triangular bract about 1.5-2 mm long, similar to other Cupressus and unlike the crescent-shaped, non-pointed bract on the scales of Chamaecyparis cones (Frankis, 1993). Pollination is in early spring, with the mature cones opening to release the seeds 16-20 months later. Growth is slow, and the trees can be very long-lived, with ages of over 1,600 years reported (Brown 1996).

Origin
Nootka Cypress is native to the west coast of North America, from the Prince William Sound area in Alaska, south to northwesternmost California, typically occurring on wet sites in mountains, often close to the tree line, but sometimes also at lower altitudes. It derives its name from its discovery at Nootka Sound on Vancouver Island, British Columbia.

Cultivation
Nootka Cypress is a popular ornamental tree in gardens, grown for its elegant weeping foliage. Several cultivars have been named. Inertia and conservatism in the horticultural and forestry industries (both notoriously slow to adopt the results of botanical research) mean the name Chamaecyparis nootkatensis is likely to continue being listed in these situations for a long time yet. It is also sometimes called Yellow Cypress, and sometimes wrongly called a cedar (Cedrus), due to confusion by early European settlers of its scented wood with the unrelated but somewhat similarly scented wood of cedars; this misapplication should be avoided (Kelsey & Dayton 1942).

Nootka Cypress is one of the parents of the very popular garden hybrid Leyland Cypress Cupressus × leylandii (syn. × Cupressocyparis leylandii, × Cuprocyparis leylandii); the other parent being Cupressus macrocarpa (Monterey Cypress).

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