Hesperocyparis forbesii was given its first scientific description by the Californian botanist
Willis Linn Jepson in 1922. It was named
Cupressus forbesii by him. Research into the genetics of
Cupressus and
Juniperus as a whole resulted in a number of proposed reorganizations of the genus. The 2009 publication by Jim A. Bartel and others moving most of the North American species to a new genus
Hesperocyparis is the proposal that found most acceptance. the name
Hesperocyparis forbesii is listed as the accepted species name by
Plants of the World Online, and the USDA
Natural Resources Conservation Service PLANTS database.
Hesperocyparis guadalupensis is
endemic to
Guadalupe Island off Baja California, two hundred fifty miles away from any
H. forbesii stands. Molecular testing has shown
Hesperocyparis guadalupensis to be slightly more closely related to
Hesperocyparis stephensonii. Major differences between Tecate cypress (
Hesperocyparis forbesii) and Guadalupe cypress (
Hesperocyparis guadalupensis) are: • Guadalupe cypress, when mature, makes a much more massive and taller tree than Tecate cypress. • Guadalupe cypress has glaucous, somewhat blue-tinted foliage, while Tecate cypress has very green foliage. • Guadalupe cypress cones will open without fire, while Tecate cypress cones differ from any other species of California Cypress, in that even once disconnected from the parent tree, they will not open without heat. ==Ecology==