A genus of lofty evergreen trees allied to Cupressus, differing from it in their usually flattened sprays of branchlets, smaller cones usually ripening the first year, and by each cone-scale bearing only two, rarely three to five seeds. All save one – C. thyoides of eastern N. America – are natives of the lands bordering the Pacific Ocean, two in western N. America and the other three in Formosa and Japan. With the exception of C. formosensis all the species are hardy and comprise some of the very finest of ornamental evergreens. They like abundant moisture and a deep loamy soil, and can be increased by cuttings as well as by seeds.
The leaves of seedling and juvenile plants of Chamaecyparis (also of Cupressus and Thuja) are very different from those of adult trees, being needle-like or awl-like, up to 1⁄3 in. long and spreading. Individuals of some species show the remarkable characteristic of retaining this juvenile type of foliage permanently or, at any rate, for an indefinite period, and thereby have originated some very pretty garden trees. The juvenile form of C. pisifera known as ‘Squarrosa’ is so distinct from the type in its foliage that Siebold and Zuccarini (Flora Japonica, 1842) treated it as a distinct species of the genus Retinispora alongside the two wild Japanese cypresses, which also received their first descriptions in that work as Retinispora pisifera and obtusa. Later botanists transferred R. pisifera and obtusa to Cupressus or Chamaecyparis. As for Retinispora squarrosa its true nature was soon revealed through the raising of seedlings and the appearance of occasional reversion shoots with normal adult foliage. But in gardens the generic name, corrupted to “Retinospora”, continued to be used for the juvenile forms.
Some juvenile forms of more recent origin, having produced neither cones nor reversion shoots, still cannot be placed with certainty, either as to species or even to genus (see C. obtusa ‘Sanderi’ and C. thyoides ‘Ericoides’).