Flora of North America species comparison

The two varieties recognized in the flora are indistinguishable in reproductive characteristics and continuously intergrading in morphologic and phenologic characteristics, although pure populations of the extremes appear morphologically and ecologically distinct. Unlike the varieties in the flora, var. mexicanum is annually cladoptosic, with determinate short shoots abscising concomitantly with expansion of shoots of the following year. Specimens from juvenile individuals, stump sprouts, fertile branchlets, terminal vegetative branchlets, or late-season growth may not be determinable to variety.

Taxodium distichum (baldcypress) is the state tree of Louisiana.

Varieties 3 (2 in the flora).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Pollination usually occurs in late winter or spring but may occur anytime from late summer to early winter for some species of Juniperus. Seed maturation occurs in late summer or autumn. Species of Cupressus have serotinous cones that remain closed for many years, some opening only after exposure to fire.

The Cupressaceae, with a known fossil record extending back to the Jurassic (C. N. Miller Jr. 1988), constitute a diverse family often divided between Cupressaceae in the strict sense (for genera with leaves opposite in four ranks or whorled) and Taxodiaceae (leaves mostly alternate), but they are best kept together (J. E. Eckenwalder 1976; R. A. Price 1989). The unity of the family is best shown in the structure of the mature seed cones: the bract-scale complexes are intimately fused for most of their common length, the 1–20 ovules are erect at first but may invert with maturity, and the paired seed wings, if present, are derived from the seed coat. A majority of genera are monotypic and most others display disjunct or relictual distributions, even though individual species may be widely distributed. Only bird-dispersed Juniperus is species rich, with a wide, nearly continuous Northern Hemisphere distribution. Because of their uniformity, seedlings and juvenile specimens may not be determinable to genus. Foliage of cultivars may deviate greatly from forms found in wild plants.

Although no members of the family attain dominance over immense geographic spans as do some species of the Pinaceae in the boreal forests, they can achieve considerable local and regional prominence. Examples include redwood (Sequoia sempervirens) along the coast of northern California, several species of Juniperus (together with pinyons) at moderate elevations in the southwestern United States and Mexico, and baldcypress (Taxodium distichum) in deep swamps of the southeastern United States. Their ranges and regions of dominance were considerably greater during the early Tertiary.

The heartwood of many species of Cupressaceae is resistant to termite damage and fungal decay, and therefore it is widely used in contact with soil. Most prominent in the flora are redwood and baldcypress; the premier coffin wood of China, Cunninghamia lanceolata, is another member of the family. Other genera, usually called cedars, may have aromatic woods with a variety of specialty uses. Wooden pencils are made from incense-cedar (Calocedrus decurrens) and eastern redcedar (Juniperus virginiana), which is also used for lining cedar chests. Wood from species of Thuja is still used for cedar roofing shingles.

In addition to the taxa treated below (including one naturalized species), several additional species and genera are cultivated to a greater or lesser extent and may persist without spreading after abandonment of cultivation. Some of the more important cultivated species of genera not treated in the flora include: Cryptomeria japonica (Linnaeus f.) D. Don (Japanese-cedar), differing from Sequoiadendron in its smaller, globose cones with bract/scale complexes bearing five to eight teeth; Cunninghamia lanceolata (Lambert) Hooker (China-fir), unlike all North American native taxa in its pointed, flat, lanceolate, drooping leaves to 7 cm; Metasequoia glyptostroboides Hu & W. C. Cheng (dawn-redwood), differing from Sequoia in its opposite leaves and deciduous branchlets and from Taxodium in its opposite leaves and persistent seed-cone scales; Microbiota decussata Komarov (microbiota), differing from spreading junipers in its minute, opening, one-seeded cone; Platycladus orientalis (Linnaeus) Franco [Thuja orientalis Linnaeus; Biota orientalis (Linnaeus) Endlicher; oriental arborvitae], which may escape locally from cultivation, differing from Thuja in its vertical sprays of branchlets, thicker, fleshier bract/scale complexes with prominent hornlike umbos, and unwinged seeds; and Thujopsis dolabrata (Linnaeus f.) Siebold & Zuccarini (hiba arborvitae), differing from Thuja in its much broader lateral leaf pairs and its sprays of branchlets with prominent white waxy markings beneath.

Genera 25–30, species 110–130 (9 genera, 30 species in the flora).

(Discussion copyrighted by Flora of North America; reprinted with permission.)