"Cupressus" × "leylandii" is a hybrid of two other cypress species: Monterey cypress ("Cupressus macrocarpa") and Nootka cypress ("Cupressus nootkatensis"). The taxonomic status of Nootka cypress has changed over time, and this has affected the taxonomic status of the hybrid. Nootka cypress was first regarded as belonging in the genus "Cupressus", but was later placed in "Chamaecyparis". It has become clear, however, that when the genus "Cupressus" is defined to include "Chamaecyparis", it is paraphyletic unless it also includes "Juniperus". In 2004, Little et al. transferred the Nootka cypress to "Callitropsis". Little (2006) proposed another alternative by transferring all the North American species of "Cupressus", including the Monterey cypress ("C. macrocarpa"), to "Callitropsis".