Bald Cypress Taxodium distichum Knees High DoF

A cypress knee is a distinctive structure forming above the roots of a

cypress Cypress is a common name for various coniferous trees or shrubs from the ''Cupressus'' genus of the '' Cupressaceae'' family, typically found in temperate climates and subtropical regions of Asia, Europe, and North America. The word ''cypress'' ...

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, e.g., including only woody plants with secondary growth, only ...

of any of various species of the subfamily

Taxodioideae Taxodioideae is a subfamily in Cupressaceae Cupressaceae or the cypress family is a family of conifers. The family includes 27–30 genera (17 monotypic), which include the junipers and redwoods, with about 130–140 species in total. They ar ...

, such as the

bald cypress ''Taxodium distichum'' (baldcypress, bald-cypress, bald cypress, swamp cypress; ; ''cipre'' in Louisiana) is a deciduous conifer in the family Cupressaceae. It is native to the southeastern United States. Hardy and tough, this tree adapts to a w ...

. Their function is unknown, but they are generally seen on trees growing in

swamp A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...

s. Cypress knees can grow to considerable size. The largest on record, along the Cache River in northeastern Arkansas, is high and diameter at water level. while the tallest, along the Suannee River in North Florida, is in height. Some current hypotheses state that they might help to aerate the tree's roots, create a barrier to catch sediment and reduce erosion, assist in anchoring the tree in the soft and muddy soil, or any combination thereof. Knees are

wood Wood is a structural tissue/material found as xylem in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulosic fibers that are strong in tension and embedded in a matrix of lignin t ...

y projections sent above the normal water level, roughly vertically from the

root In vascular plants, the roots are the plant organ, organs of a plant that are modified to provide anchorage for the plant and take in water and nutrients into the plant body, which allows plants to grow taller and faster. They are most often bel ...

s, with a near-right-angle bend taking them vertically upward through water. One early assumption of their function was that they provided oxygen to the roots that grow in the low-dissolved-

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

(DO) waters typical of a swamp, acting as

pneumatophores Aerial roots are roots growing above the ground. They are often adventitious, i.e. formed from nonroot tissue. They are found in diverse plant species, including epiphytes such as orchids (''Orchidaceae''), tropical coastal swamp trees such ...

mangrove A mangrove is a shrub or tree that grows mainly in coastal saline water, saline or brackish water. Mangroves grow in an equatorial climate, typically along coastlines and tidal rivers. They have particular adaptations to take in extra oxygen a ...

s have similar adaptations. There is little actual evidence for this assertion; in fact, swamp-dwelling specimens whose knees are removed continue to thrive, and laboratory tests demonstrate that the knees are not effective at depleting oxygen in a sealed chamber. Even though there is no expert consensus on their role, the supposition that they are pneumatophores is repeated without comment in several introductory botany textbooks. Another more likely function is that of structural

buttress A buttress is an architectural structure built against or projecting from a wall which serves to support or reinforce the wall. Buttresses are fairly common on more ancient (typically Gothic) buildings, as a means of providing support to act ...

ed support and stabilization. Lowland or swamp-grown cypresses found in flooded or flood-prone areas tend to be buttressed and "kneed," as opposed to cypresses grown on higher ground, which may grow with very little taper. Trees that develop these "knees" include: * ''

Glyptostrobus ''Glyptostrobus'' is a small genus of conifers in the family Cupressaceae (formerly in the family Taxodiaceae). The sole living species, '' Glyptostrobus pensilis'', is native to subtropical southeastern China, from Fujian west to southeast Yu ...

'' *

Bald cypress ''Taxodium distichum'' (baldcypress, bald-cypress, bald cypress, swamp cypress; ; ''cipre'' in Louisiana) is a deciduous conifer in the family Cupressaceae. It is native to the southeastern United States. Hardy and tough, this tree adapts to a w ...

* Pond cypress *

Ahuehuete ''Taxodium mucronatum'', commonly known as Montezuma bald cypress, Montezuma cypress, or ahuehuete, is a species of ''Taxodium'' that is primarily native to Mexico and Guatemala, with a few populations in the southwestern United States. Ahuehue ...

Metasequoia ''Metasequoia'', or dawn redwood, is a genus of fast-growing coniferous trees. It contains one extant (living) species, ''Metasequoia glyptostroboides'', which is one of three extant species of conifers known as redwoods in the world. ''Metaseq ...

Also the unrelated ''

Sonneratia caseolaris ''Sonneratia caseolaris'', commonly known as mangrove apple, or pagatpat is a species of plant in the family Lythraceae. The fruit is noted for its outward similarity to the persimmon fruit. This tree is a type of mangrove growing up to 20 m in ...

'' (

Lythraceae Lythraceae is a family (biology), family of flowering plants, including 32 genus, genera, with about 620 species of Herbaceous plant, herbs, shrubs, and trees. The larger genera include ''Cuphea'' (275 spp.), ''Lagerstroemia'' (56), ''Nesaea (pl ...

) has knees very similar to those of ''Taxodium distichum''.

References

External links

*Christopher H. Briand.
Cypress Knees: An Enduring Enigma
." Arnoldia. 2000-2001.Vol. 60(4). p. 19-20, 21-25. An extensive review of the published literature concerning cypress knees. {{DEFAULTSORT:Cypress Knee Cupressaceae Plant roots

See also

References

External links