bald cypress

Taxodium
Bald Cypress forest in a central Mississippi lake
Scientific classification
Kingdom:	Plantae
Division:	Pinophyta
Class:	Pinopsida
Order:	Pinales
Family:	Cupressaceae
Subfamily:	Taxodioideae[1]
Genus:	Taxodium Rich.
Species
Taxodium ascendens - Pond Cypress Taxodium distichum - Bald Cypress Taxodium mucronatum - Montezuma Cypress

Taxodium (pronounced /tækˈsoʊdiəm/)^[2] is a genus of one to three species (depending on taxonomic opinion) of extremely flood-tolerant conifers in the cypress family, Cupressaceae. Within the family, Taxodium is most closely related to Chinese Swamp Cypress (Glyptostrobus pensilis) and Sugi (Cryptomeria japonica).

Species of Taxodium occur in the southern part of the North American continent and are deciduous in the north and semi-evergreen to evergreen in the south. They are large trees, reaching 100–150 ft (30–46 m) tall and 2–3 m (6.6–9.8 ft) (exceptionally 11 m/36 ft) trunk diameter. The needle-like leaves, 0.5–2 cm (0.20–0.79 in) long, are borne spirally on the shoots, twisted at the base so as to appear in two flat rows on either side of the shoot. The cones are globose, 2–3.5 cm (0.79–1.4 in) diameter, with 10-25 scales, each scale with 1-2 seeds; they are mature in 7-9 months after pollination, when they disintegrate to release the seeds. The male (pollen) cones are produced in pendulous racemes, and shed their pollen in early spring.

Species

The three taxa of Taxodium are treated here as distinct species, though some botanists treat them in just one or two species, with the others considered as varieties of the first described. The three are distinct in ecology, growing in different environments, but hybridise where they meet.

• Taxodium ascendens Brongn. - Pond Cypress

The Pond Cypress occurs within the range of Bald Cypress, but only on the southeastern coastal plain from North Carolina to Louisiana. It occurs in still blackwater rivers, ponds and swamps without silt-rich flood deposits.

• Taxodium distichum (L.) Rich. - Bald Cypress

The most familiar species in the genus is the Bald Cypress, native to much of the southeastern United States, from Delaware to Texas, especially Louisiana and inland up the Mississippi River to southern Indiana. It occurs mainly along rivers with silt-rich flood deposits.

• Taxodium mucronatum Ten., 1853 - Montezuma Cypress, Ahuehuete

The Montezuma Cypress occurs from the Lower Rio Grande Valley south to the highlands of southern Mexico, and differs from the other two species in being substantially evergreen. A specimen in Santa María del Tule, Oaxaca, the Árbol del Tule, is 43 m (140 ft) tall and has the second greatest trunk thickness of all trees, 11.42 m (37.5 ft) in diameter. It is a riparian tree, occurring on the banks of streams and rivers, not in swamps like the Bald and Pond Cypresses.

Uses

Cypress knees at low water, Wee Tee Lake, South Carolina

The trees are especially prized for their wood, of which the heartwood is extremely rot and termite resistant. The heartwood contains a sesquiterpene called cypressene,^[3] which acts as a natural preservative. It takes decades for cypressene to accumulate in the wood, so lumber taken from old-growth trees is more rot resistant than that from second-growth trees.^[4] However, age also increases susceptibility to Pecky Rot fungus (Stereum taxodii), which attacks the heartwood and causes some damaged trees to become hollow and thus useless for timber. Bald Cypress wood was much used in former days in the southeastern United States for roof shingles.^[5] The shredded bark of these trees is used as a mulch, although the current harvest rate for this product is unsustainable and is causing substantial environmental damage especially in the south where cutting boundaries are not being followed.

Evolution

Fossil leave of Taxodium dubium, 8 Mio. years old, Hambach lignite open cast mine, Germany

In earth's history Taxodium was widespread. It is known since the Jurassic and can be found as fossil e.g. in layers from Tertiary times.

References

External links

• Gymnosperm Database - Taxodium
• Corkscrew Swamp Sanctuary website
• National Audubon Society, undated. Corkscrew Swamp Sanctuary. A Companion Field Guide. Artype Inc., Ft. Myers. 25 p.