Leyland Cypress - Taxonomic Status of Nootka Cypress

Taxonomic Status of Nootka Cypress

The taxonomic status of Nootka Cypress is disputed; in the past, it was widely regarded as belonging in the genus Chamaecyparis, and in 2002 it was classified in a new genus Xanthocyparis. In 2004, Little et al. transferred it to Callitropsis. Little (2006) proposed another alternative by transferring all the North American species of Cupressus, including the Monterey Cypress, to Callitropsis. In any of these classifications, the hybrids become very unusual in being intergeneric hybrids, the only ones ever reported among the Gymnosperms. In fact the very existence of these hybrids, and their ease of formation, is a further strong pointer (in addition to genetic and morphological evidence) for the treatment of Nootka cypress in Cupressus. In 2010, Mao et al. performed a more detailed molecular analysis and placed Nootka Cypress to Cupressus. It may be added that attempts to cross Nootka cypress with other Chamaecyparis species have been universally unsuccessful. Where Nootka Cypress is treated in Chamaecyparis, the name of the hybrid becomes × Cupressocyparis leylandii, and where treated in Xanthocyparis, it becomes × Cuprocyparis leylandii.

Two other similar hybrids have also been raised, both involving Nootka Cypress with other Cupressus species:

Cupressus arizonica var. glabra × Cupressus nootkatensis (Cupressus × notabilis)

Cupressus lusitanica × Cupressus nootkatensis (Cupressus × ovensii)