Callitropsis nootkatensis

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Nootka Cypress (Callitropsis nootkatensis), formerly Cupressus nootkatensis, Xanthocyparis vietnamensis or Chamaecyparis nootkatensis, is a cypress (Cupressaceae) with a chequered taxonomic and nomenclatural history. First described in the genus Cupressus as Cupressus nootkatensis in 1824, it was transferred to Chamaecyparis in 1841 on the basis of its foliage being in flattened sprays, as in other Chamaecyparis, but unlike most (though not all) other Cupressus species.

However, this placement does not fit with the morphology and phenology of the cones, which are far more like Cupressus, like them maturing in two years, not one. Genetic evidence, published by Gadek et al. (2000), 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 Vietnamese Golden Cypress Xanthocyparis vietnamensis; this species is remarkably similar to Nootka Cypress and the treatment has many arguments in its favour, as while they are not related to Chamaecyparis, neither do they fit fully in Cupressus despite the many similarities.

Finally, Little et al. (2004), while confirming the above relationship with further evidence, pointed out that an earlier nomenclatural combination in the genus Callitropsis existed, as Callitropsis nootkatensis (D. Don) Örsted, published in 1864 but overlooked or ignored 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.

Nootka Cypress is native to the west coast of North America, from the Kenai Peninsula in Alaska, south to northernmost California, typically occurring on wet sites in mountains, often close to the tree-line, but sometimes also at lower altitudes.

It is an evergreen tree to 40 m tall, commonly with pendulous branches. The foliage is in flat sprays, with dark green, 3-5 mm long scale-leaves. The cones have 4 scales (occasionally 6 scales), and resemble the cones of Mexican Cypress (Cupressus lusitanica, another Cupressus species which can show foliage in flat sprays) fairly closely, except being somewhat smaller, typically 10-14 mm diameter; each scale has a pointed triangular bract about 1.5-2 mm long, again similar to other Cupressus and unlike the crescent-shaped, non-pointed bract on the scales of Chamaecyparis cones.

It is one of the parents of the hybrid Leyland Cypress; as the other parent, Monterey Cypress, is also in genus Cupressus, the ready formation of this hybrid is a further argument for the placement of the Nootka cypress close to Cupressus.

Its name derives from its discovery on the lands of the Nootka people, Native Americans of Vancouver Island, British Columbia. It is also known as Yellow Cypress and Alaska Cypress, and also (very confusingly, as it is not a cedar), as Yellow Cedar or Alaska Cedar.

References

• Gadek, P. A., Alpers, D. L., Heslewood, M. M., & Quinn, C. J. 2000. Relationships within Cupressaceae sensu lato: a combined morphological and molecular approach. American Journal of Botany 87: 1044–1057. Abstract
• Farjon, A., Hiep, N. T., Harder, D. K., Loc, P. K., & Averyanov, L. 2002. A new genus and species in the Cupressaceae (Coniferales) from northern Vietnam, Xanthocyparis vietnamensis. Novon 12: 179–189.
• Little, D. P., Schwarzbach, A. E., Adams, R. P. & Hsieh, Chang-Fu. 2004. The circumscription and phylogenetic relationships of Callitropsis and the newly described genus Xanthocyparis (Cupressaceae). American Journal of Botany 91 (11): 1872–1881. Abstract