Taxodium
| Scientific classification |
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| Species |
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Taxodium ascendens - Pond Cypress
- Status: Secure
Taxodium distichum - Bald Cypress
- Status: Secure
Taxodium mucronatum - Montezuma Cypress
- Status: Data Deficient
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Taxodium is a genus of one to three species (depending on taxonomic opinion) of conifers in the Family Cupressaceae, one of several genera in the family known as cypresses. 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 30-45 m tall and 2-3 m (exceptionally 11 m) trunk diameter. The needle-like leaves, 0.5-2 cm 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 diameter, with 10-25 scales, each 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 listed 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.
Bald Cypress
The most familiar cypress in the Genus Taxodium is the Bald Cypress (Taxodium distichum), also known as Southern Cypress or Swamp Cypress, native to much of the southeastern United States, from Delaware to Texas and inland up the Mississippi River to southern Indiana. The trees are called 'bald' because, unlike other cypresses, they lose their leaves during the winter months.
Ancient Bald Cypress forests, with some trees over 1200 years old, once dominated swamps in the Southeast. The largest remaining stand of Bald Cypress is at Corkscrew Swamp Sanctuary. These trees are around 500 years of age and some now exceed 40m (130 ft) in height. The Bald cypress occurs mainly along riparian (riverside) wetlands subject to periodic flooding by silt-rich 'brownwater' rivers.
Bald Cypress trees in swamp situations have a peculiarity of growth called cypress knees. These are woody projections sent above the water from the roots. Their function is thought to be to provide oxygen to the roots that grow in the low dissolved oxygen (DO) waters typical of a swamp (see also mangroves, which have similar adaptations).
The Bald Cypress was designated the official state tree of Louisiana in 1963.
Pond Cypress
The Pond Cypress (Taxodium ascendens or T. distichum var. imbricatum) is usually smaller than the Bald Cypress, and the bark is a lighter gray. The leaves are shorter, slenderer and are on shoots that tend to be erect rather than spreading. It occurs within the range of Bald Cypress, but only on the southeastern coastal plain from North Carolina to Louisiana. It differs in ecology, occurring mainly in still blackwater rivers, ponds and swamps without silt-rich flood deposits.
Montezuma Cypress
The Montezuma Cypress (Taxodium mucronatum or T. distichum var. mucronatum) from the Rio Grande south to the highlands of southern Mexico differs from the other two species in being substantially evergreen. A specimen at Santa Maria del Tule in Oaxaca has the greatest trunk thickness of any living tree: 11.42 m in diameter. It is a riparian tree, occurring on the banks of streams and rivers, not in swamps like the Bald and Pond cypress.
Uses
The trees are especially prized for their wood, of which the heartwood is extremely rot and termite resistant. Bald Cypress wood was much used in former days in southeastern US for shingles. The shredded bark of these trees is a popular mulch, although the current harvest rate for this product is not sustainable and is causing substantial environmental damage.
External link and Reference
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- National Audubon Society, undated. Corkscrew Swamp Sanctuary. A Companion Field Guide. Artype Inc., Ft. Meyers. 25 p.
