Carex decomposita - Muhl.
Cypress-knee Sedge
Other English Common Names: Decomposite Sedge
Other Common Names: cypress-knee sedge
Taxonomic Status: Accepted
Related ITIS Name(s): Carex decomposita Muhl. (TSN 39389)
Unique Identifier: ELEMENT_GLOBAL.2.154855
Element Code: PMCYP033K0
Informal Taxonomy: Plants, Vascular - Flowering Plants - Sedge Family
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Monocotyledoneae Cyperales Cyperaceae Carex
Check this box to expand all report sections:
Concept Reference
Concept Reference: Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Concept Reference Code: B94KAR01HQUS
Name Used in Concept Reference: Carex decomposita
Taxonomic Comments: Distinct species in very large genus.
Conservation Status

NatureServe Status

Global Status: G3G4
Global Status Last Reviewed: 29Apr2010
Global Status Last Changed: 29Apr2010
Rounded Global Status: G3 - Vulnerable
Reasons: Carex decomposita is primarily a southern species, with historical range from New York and Michigan south to northern Florida and eastern Texas; range seems to have contracted somewhat within the last century, particularly in the north and east. Approximately 100-130 occurrences are believed extant, with Missouri, Louisiana, Mississippi, and the Carolinas containing the greatest numbers. Somewhat undercollected; new sites continue to be discovered. C. decomposita's wetland habitats have declined significantly from their historical extent due to extensive wetland drainage, and the species' sensitivity to drastic changes in water levels makes it vulnerable to certain hydrological alterations. Current threats include (1) wetland drainage for agriculture and housing, (2) unnatural water level fluctuations due to hydrological modifications within watersheds, (3) conversion of ponds to stock watering holes and pond degradation due to grazing, (4) habitat degradation due to logging, (5) herbicide use, (6) road grading, and (7) invasion of habitat by water hyacinth. These issues are causing declines in some parts of the range, although habitat availability may actually be increasing in some areas due to hydrological modifications that create slow waters and thus vegetation mats that C. decomposita can use as habitat.
Nation: United States
National Status: N3

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Alabama (S1), Arkansas (S2), Delaware (S1), District of Columbia (SH), Florida (SNR), Georgia (S2?), Illinois (S1), Indiana (S2), Kentucky (S2), Louisiana (S3), Maryland (S1), Michigan (SX), Mississippi (S3), Missouri (S3), New York (SH), North Carolina (S2), Ohio (S1), Oklahoma (S1), South Carolina (S2), Tennessee (S2), Texas (S1), Virginia (S1)

Other Statuses

NatureServe Global Conservation Status Factors

Range Extent Comments: Primarily a southern species, once ranging from New York to Michigan southward to northern Florida and eastern Texas (Crispin and Penskar 1990). The range of this species seems to have retreated within the last century, particularly in the north and east. The most northerly extant site occurs in southern Ohio; possibly extirpated in New York, Maryland, and Michigan.

Number of Occurrences: 81 - 300
Number of Occurrences Comments: Approximately 100-130 occurrences are believed extant, with Missouri, Louisiana, Mississippi, and the Carolinas containing the greatest occurrence numbers (all other states have < 10 extant occurrences). An additional 35 occurrences are considered historical or extirpated. New sites continue to be discovered; several new occurrences have been found in at least Arkansas and Georgia in the past couple years (T. Witsell and T. Patrick, pers. comm. 2010).

Population Size Comments: Some occurrences are quite small; in some cases, this is because they inhabit wetlands of very limited extent (e.g., sinkhole ponds in Missouri). Nevertheless, numerous occurrences with 100+ plants have been documented, and at least one with thousands of plants is known.

Number of Occurrences with Good Viability/Integrity: Many (41-125)
Viability/Integrity Comments: Rangewide, approximately 55 occurrences are believed to have excellent or good viability, and another 40 or so have not yet been assessed (some of these may be ranked excellent or good once assessments are completed).

Overall Threat Impact: High - medium
Overall Threat Impact Comments: Overall, this species does not seem to be highly threatened at present, but there are definitely challenges to the persistence of some populations.

Wholesale destruction of wetlands by draining for agriculture and housing developments is a significant threat (Cusick pers. comm., Evans pers. comm., Smith pers. comm.). Populations have likely been destroyed through the years due to these activities. Due to the rapid urbanization of the Virginia coastal region, populations may be destroyed through habitat destruction, water quality degradation, and boat-wake disturbances (Ludwig pers. comm.).

Dredging of stream and rivers, coupled with the drainage of upland wetlands, has quickened the run-off of spring melt-waters and rainfall. Excessive run-off over a shortened period of time has likely had detrimental effects on historical C. decomposita populations by increasing the height of flood waters and affecting new habitats. Apparently, the species is not able to survive in areas where water levels fluctuate significantly throughout the year (Bryson per. comm.); it is only found in old oxbow swamps away from the current flooding regime, sinkhole ponds and other wetlands of this sort. Natural upland cover and wetlands within the watersheds should be restored and/or protected.

Conversion of natural ponds to stock watering holes through the deepening and removal of native vegetation is also a significant threat to the species (Smith pers. comm.). Other natural ponds may experience degradation due to grazing during periods of prolonged drought.

Logging of habitat has also apparently been a threat to C. decomposita. Evans (pers. comm.) stated that populations in western Kentucky have undoubtedly been destroyed in the past due to drainage and clearing of the extensive wetlands in that part of the state.

The log sedge is apparently only found in areas that are not subjected to herbicide use (Bryson pers. comm.). In areas adjacent to rice fields, herbicide (2-4-D or 2-4-5-T) use has eliminated the species (Bryson pers. comm.).

Road grading of populations located on roadbanks within swamps is a threat to such populations in Illinois (Schwegman pers. comm.). Shifting ice sometimes takes out dead snags and the plants associated with them (Schwegman pers. comm.).

In at least Arkansas, water hyacinth is becoming a serious issue; at least two Arkansas sites are impacted.

Short-term Trend: Decline of <30% to relatively stable
Short-term Trend Comments: In some parts of its range, this species appears to be declining due to habitat conversion and drainage. In other areas, available habitat appears to be increasing. For example, in Arkansas, the Arkansas River was converted to series of lakes in the 1950s, creating slow waters with alligator weed mats that are colonized by this species (T. Witsell pers. comm. 2010); floating mats of vegetation seem to be generally increasing in Arkansas, and perhaps elsewhere. In some states, population trends are mixed; for example, in Kentucky, some populations are stable and some are declining with changes in hydrology (D. White pers. comm. 2010).

Long-term Trend: Decline of 50-70%
Long-term Trend Comments: Range seems to have retreated within the last century, particularly in the north and east; this species is now possibly extirpated in New York, Maryland, and Michigan. The wetland habitats preferred by C. decomposita have declined significantly from their historical extent due to extensive wetland drainage.

Intrinsic Vulnerability Comments: Does not occupy all of its 'suitable' habitat. Very susceptible to drastic changes in water levels.

Other NatureServe Conservation Status Information

Global Range: Primarily a southern species, once ranging from New York to Michigan southward to northern Florida and eastern Texas (Crispin and Penskar 1990). The range of this species seems to have retreated within the last century, particularly in the north and east. The most northerly extant site occurs in southern Ohio; possibly extirpated in New York, Maryland, and Michigan.

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map

U.S. & Canada State/Province Distribution
United States AL, AR, DC, DE, FL, GA, IL, IN, KY, LA, MD, MIextirpated, MO, MS, NC, NY, OH, OK, SC, TN, TX, VA

Range Map
No map available.

U.S. Distribution by County Help
State County Name (FIPS Code)
AL Henry (01067), Jackson (01071), Jefferson (01073), Madison (01089), Talladega (01121)*
AR Ashley (05003), Clark (05019), Drew (05043)*, Faulkner (05045), Garland (05051), Hempstead (05057), Hot Spring (05059), Jefferson (05069), Little River (05081), Miller (05091)*, Pike (05109), Polk (05113), Pulaski (05119), Saline (05125), Union (05139)
DE New Castle (10003)
GA Baker (13007)*, Camden (13039), Crisp (13081)*, Decatur (13087)*, Dooly (13093)*, Glynn (13127), Lowndes (13185), Seminole (13253)*, Sumter (13261)*
IL Johnson (17087), Pope (17151)*, Pulaski (17153), Union (17181)
IN Allen (18003), Delaware (18035)*, Harrison (18061), Henry (18065), Lawrence (18093)*, Owen (18119)
KY Carlisle (21039)*, Edmonson (21061), Hart (21099), Hickman (21105), Logan (21141), Marshall (21157)
LA Bienville (22013), Bossier (22015), Caddo (22017), Franklin (22041), Grant (22043), Jackson (22049), Jefferson (22051), Lafourche (22057), Ouachita (22073), St. Martin (22099), St. Mary (22101), St. Tammany (22103), Tensas (22107)
MD Montgomery (24031)
MO Bollinger (29017), Carter (29035), Dent (29065)*, Dunklin (29069)*, Howell (29091), Oregon (29149), Reynolds (29179), Ripley (29181), Shannon (29203), Texas (29215)
MS Adams (28001)*, Amite (28005), Attala (28007), Bolivar (28011), Coahoma (28027), Franklin (28037), Grenada (28043), Jefferson Davis (28065)*, Leflore (28083), Marshall (28093), Pearl River (28109), Pike (28113), Rankin (28121), Simpson (28127), Washington (28151)
NC Brunswick (37019), Chowan (37041), Cumberland (37051), Gates (37073), New Hanover (37129)*, Richmond (37153), Scotland (37165), Warren (37185)*
NY Livingston (36051)*, Monroe (36055)*, Oneida (36065)*, Ontario (36069)*, Seneca (36099)*, Yates (36123)*
OH Franklin (39049), Licking (39089)
OK Atoka (40005)*
SC Barnwell (45011), Calhoun (45017), Charleston (45019), Clarendon (45027), Colleton (45029), Orangeburg (45075), Sumter (45085)
TX Liberty (48291), Marion (48315)*, Smith (48423), Wood (48499)
VA Chesapeake (City) (51550), Fairfax (51059)*, Greensville (51081), Isle of Wight (51093)*, King and Queen (51097), Loudoun (51107)*, Southampton (51175), Surry (51181)*, Sussex (51183)*, Virginia Beach (City) (51810), Williamsburg (City) (51830)*
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
02 Mohawk (02020004)+*, Brandywine-Christina (02040205)+, Middle Potomac-Catoctin (02070008)+, Middle Potomac-Anacostia-Occoquan (02070010)+*, Great Wicomico-Piankatank (02080102)+, Lower James (02080206)+*
03 Nottoway (03010201)+, Blackwater (03010202)+, Ghowan (03010203)+, Albemarle (03010205)+, Fishing (03020102)+*, Upper Cape Fear (03030004)+, Lower Cape Fear (03030005)+, Black (03030006)+, Lower Pee Dee (03040201)+, Little Pee Dee (03040204)+, Lake Marion (03050111)+, Santee (03050112)+, Salkehatchie (03050207)+, Bulls Bay (03050209)+*, Middle Savannah (03060106)+, Altamaha (03070106)+, Satilla (03070201)+, withlacoochee (03110203)+, Lower Chattahoochee (03130004)+, Middle Flint (03130006)+*, Lower Flint (03130008)+*, Ichawaynochaway (03130009)+*, Spring (03130010)+*, Middle Coosa (03150106)+*, Locust (03160111)+, Upper Pearl (03180001)+, Middle Pearl-Strong (03180002)+, Middle Pearl-Silver (03180003)+*, Lower Pearl. Mississippi (03180004)+
04 Lower Genesee (04130003)+*, Seneca (04140201)+*
05 Muskingum (05040004)+, Upper Scioto (05060001)+, Upper Green (05110001)+, Eel (05120104)+, Upper White (05120201)+, Lower White (05120202)+, Lower East Fork White (05120208)+*, Red (05130206)+, Blue-Sinking (05140104)+, Lower Ohio-Bay (05140203)+*, Lower Ohio (05140206)+
06 Guntersville Lake (06030001)+, Wheeler Lake (06030002)+, Kentucky Lake (06040005)+, Lower Tennessee (06040006)+
07 Upper Mississippi-Cape Girardeau (07140105)+, Whitewater (07140107)+, Cache (07140108)+
08 Lower Mississippi-Memphis (08010100)+*, Bayou De Chien-Mayfield (08010201)+, Lower St. Francis (08020203)+, Little River Ditches (08020204)+, Little Tallahatchie (08030201)+, Tallahatchie (08030202)+, Coldwater (08030204)+, Yalobusha (08030205)+, Upper Yazoo (08030206)+, Big Sunflower (08030207)+, Deer-Steele (08030209)+, Ouachita Headwaters (08040101)+, Little Missouri (08040103)+, Lower Ouachita-Smackover (08040201)+, Lower Saline (08040204)+, Bayou Bartholomew (08040205)+, Lower Ouachita (08040207)+, Dugdemona (08040303)+, Little (08040304)+, Boeuf (08050001)+, Tensas (08050003)+, Homochitto (08060205)+, Tangipahoa (08070205)+, Bayou Teche (08080102)+, Vermilion (08080103)+, East Central Louisiana Coastal (08090301)+
10 Upper Gasconade (10290201)+, Big Piney (10290202)+*
11 North Fork White (11010006)+*, Upper Black (11010007)+, Current (11010008)+, Spring (11010010)+, Eleven Point (11010011)+, Lake Conway-Point Remove (11110203)+, Lower Arkansas-Maumelle (11110207)+, Muddy Boggy (11140103)+*, Clear Boggy (11140104)+*, Pecan-Waterhole (11140106)+, Lower Little (11140109)+, Mckinney-Posten Bayous (11140201)+, Middle Red-Coushatta (11140202)+, Saline Bayou (11140208)+, Black Lake Bayou (11140209)+, Lower Sulphur (11140302)+*, Cross Bayou (11140304)+, Caddo Lake (11140306)+*, Little Cypress (11140307)+*
12 Middle Sabine (12010002)+, Lake Fork (12010003)+*, Lower Trinity (12030203)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
Basic Description: Epiphytic sedge.
General Description: Cypress knee sedge is a densely tufted grass-like perennial. Its leaves are strap-like and 2.5-7.0 mm wide. Stems are 5-120 cm tall and towards its apex numerous secondary stems branch off of the main stem. Along these secondary stems as well as at the apex of the main stem are dense flower/fruit clusters (spikes). These spikes are densely arranged and are composed of separate female and male flowers. Female flowers develop into deep olive green to brown fruits (perigynia) which are 1.8-2.6 mm long (Cochrane 2002).
Technical Description: Godfrey and Wooten (1979) described C. decomposita as follows:
"Cespitose. Stems 5-10 dm tall, slender, shorter than to surpassing the leaves. Principle leaf blades 5-8 mm wide, ventral portion of sheaths whitish-papery, not loose, smooth, red-dotted. Inflorescence branched to above the middle, 5-10 cm long, the lower branches set apart, not bristly nor burlike. Some spikes staminate terminally (easily discernable only when staminate flowers at anthesis). Pistillate scales ovate, acute to short-aristate, about as long as the perigynial body. Perigynia brown at maturity, 2-2.5 mm long overall, body biconvex, obovate, nerved near the base on both sides, narrowly ribbed marginally, abruptly narrowed at the summit to a short-triangular or short-linear, usually fine-toothed beak, this shortly bidentate at the orifice. Perigynial wall very thick, closely enveloping the achene. Achene elliptic-obovate, cuneately narrowed below, the broadest portion somewhat above the middle, obtusely tapered at the summit, short-spiculate, about 1 mm long."

Diagnostic Characteristics: According to Cusick (1981) and Crispin and Penskar (1990), Carex decomposita can be much like robust C. sparganioides in appearance. C. decomposita can be distinguished by the combination of dark-colored (dark green to brown) perigynia, and leaf sheaths that are dotted with purple or red. The perigynia also contract abruptly into a short beak (Crispin and Penskar 1990). In contrast, C. sparganioides has thin, winged, light green perigynia and mottled, green and white leaf sheaths (Crispin and Penskar 1990, Cusick 1981).
Reproduction Comments: Fruiting mid April to August (FNA 2002).

Dispersal of C. decomposita may be facilitated by waterfowl (Hill 2006).

Ecology Comments: Log sedge is a relatively long-lived perennial species, bearing perigynia in mid-summer (Crispin and Penskar 1990, MI NFI 1990). Bryson (pers. comm.) stated that plants found in 1983 are still persisting in Mississippi. It is not known, however, how old these plants may be.

Carex decomposita is not a weedy species (Bryson pers. comm.). Typical populations range in size from one to several hundred (300-500) clumps in an area of 50-75 acres. Largest oxbow habitats in Mississippi range from 150-200 acres in size (Bryson pers. comm.). At the Ross Barnett Reservoir in Mississippi, a huge population explosion occurred after the cutting of the numerous cypress trees, with C. decomposita plants growing on stumps and fallen logs, trunks and branches.

Carex decomposita may require something associated with the cypress, buttonbush or tupelo bases, trunks or logs for successful germination or growth (Bryson pers. comm.). Whether this association may only serve to raise the plants above the seasonal high-water levels, or whether there is some other benefit is still unknown. Jones (pers. comm.) stated that dispersal of C. decomposita may be facilitated by wood ducks, egrets and other water birds. Seeds may be carried on the feet of the birds and fall off when they come to rest on a fallen log or cypress stump.

Estuarine Habitat(s): Herbaceous wetland
Lacustrine Habitat(s): Shallow water
Habitat Comments: Habitats include undisturbed, organic-rich backwaters, with plants occurring on floating or partially-submersed rotting logs or stumps (Reznicek pers. comm., Godfrey and Wooten 1979). The species often forms dense tussocks in the water of swamps and pond margins (Godfrey and Wooten 1979).

In Ohio, C. decomposita is an extremely rare species of very wet depressions in mixed swamp forests, occurring most frequently on hummocks, exposed logs and peaty mounds (Cusick pers. comm.). Tyrell (1987a) stated that C. decomposita was almost exclusively associated with Cephalanthus (90% of all occurrences) and less so with fallen logs. Associates include Cephalanthus occidentalis, Rosa palustris, Acer saccharinum, Ulmus americanus, Fraxinus pensylvanica, Quercus palustris and Q. bicolor (Cusick pers. comm.).

Guthrie (1989) reported C. decomposita from the bases of Taxodium trees at the water line of Reelfoot Lake, Tennessee. This habitat provides non-inundated habitats in the midst of open water and swamps in habitat that would not otherwise support the species. Associates listed within the habitat include Amorpha spp., Boehmeria cylindrica, Impatiens capensis, Lycopus rubellus, Pilea pumila, Scutellaria lateriflora and Triadenum walteri.

In Missouri, C. decomposita occurs in mountaintop depression wetlands (sinkhole ponds) on hummocks and floating vegetation mats (Smith pers. comm.). Associated species include Carex alata, C. comosa, C. lupulina and C. tribuloides. It often occurs at the base of Cephalanthus occidentalis shrubs.

Extant Michigan sites are unknown at this time, the last collection within the state having been made in the early 1900's (MI NFI 1990). Old herbarium labels indicate very wet swamps as the habitat of C. decomposita in this state (Penskar pers. comm.). These were likely buttonbush (Cephalanthus occidentalis) swamps (Reznicek pers. comm.). Historic collections were made from the vicinities of East Lansing (Ingham County) and Ann Arbor along the Raisin River (Reznicek pers. comm., Crispin and Penskar 1990, Hermann 1925). Hermann (1925) stated that although the species occurs in various rich swampy habitats, its preferred habitats appear to be on logs in ponds and at the bases of stumps or trees in swamps.

In Kentucky, C. decomposita usually grows in and around open and partially open wetlands (Evans pers. comm.). The species often grows epiphytically on the bases of cypress (Taxodium) trees. It is also found on hummocks which rise above the water in open ponds and on mounds of soil at the bases of shrubs and trees within the wetlands. Carex decomposita is often associated with other Carex species and members of the Cyperaceae.

In Arkansas, habitats include cypress knees, floating logs, floating mats, and buttonbush stands. The species seems to be able to grow in both shade and full sun. At one site, Jones (pers. comm.) found C. decomposita to be frequent on bald cypress stumps in a cypress pond, with associates around the edge of the pond including Quercus spp., Juncus spp., Coreopsis spp., Danthonia spp., Bromus purgans, Phlox pilosa and other sedges.

In North Carolina, the cypress-knee sedge is known from the base of a cypress tree (Fernald 1941), among other sites.

In Virginia, C. decomposita has been found at the edge of cypress swamps in open water at the bases of shrub and tree hummocks (Ludwig pers. comm.). Plants occur in both sunny and partially to mostly shaded situations, and also occur in fresh to oligohaline, irregularly-tidal regimes. Tidal water level flux in such habitats appears very low, approximately 4 inches (Ludwig pers. comm.). Associates include Hypericum virginicum and a species of Dichanthelium. Fernald (1941) reported finding C. decomposita at two Virginia locations. At one site, the plant was found in a wooded area between a beach and a swamp of cypress, gum and other paludal trees. Associates included Eupatorium altissimum, Malaxis floridana, Sabatia calycina, Echinodorus radicans and Kosteletzkya virginica. The second site was a swamp.

In Illinois, C. decomposita grows on emergent snags, floating logs and bases of emergent trees in swamps, and roadbanks adjoining swamps (Schwegman pers. comm.). Swayne and Bailey (1953) reported the species from the waters of Wolf Lake "Scatters", growing on logs and sides of trees. Bidens discoidea is a typical associate (Schwegman pers. comm.).

In Mississippi, C. decomposita is uncommon by virtue of its habitat, but where prime habitat can be found, C. decomposita may be abundant. The species apparently cannot tolerate the fluctuating water levels in floodplain and recent oxbow habitats that periodically flood. Populations occur predominantly in old oxbow lake situations away from the Mississippi and Yazoo Rivers (Bryson pers. comm.). Recently, due to the construction of reservoirs, C. decomposita has become relatively common in the Pearl River system. Plants always grow with their "feet" wet, occurring on cypress logs, stumps and knees, or the bases of cypress, Tupelo gum and buttonbush trees/shrubs (Bryson pers. comm., Carter et al. 1990). Roughly 90% of occurrences are associated with bald cypress. For a description of habitat occupied by C. decomposita and a close associate (C. comosa) in Coahoma County, Mississippi, see Bryson and Jones (1990). Jones (pers. comm.) described the habitat as a bald cypress slough surrounded by cultivated fields. Associates at this site included Carex comosa, Bidens spp. and a species of Lemna.

In Texas, C. decomposita is found growing on cypress stumps and logs in the open areas of old, wooded, acidic ponds. Where habitat is in good shape, populations may be large (Jones pers. comm.). Typical associates include water lilies, Ludwigia spp., Lemna spp. and a species of Wolffia. In more mesic areas around the edges of the ponds, Carex comosa, C. hyalina, C. annectens, Scirpus pendulens and S. cyperinus are found. In Wood County, plants were found infrequently in the still, shallow portions of the lake with bald cypress trees (Jones pers. comm.). Associates include Salix nigra, Nymphoides aquatica, Potamogeton diversifolius, Pontederia cordata, Peltandra virginica, Zizaniopsis miliacea, Saururus cernuus, Nuphar luteum, Nelumbo lutea, Utricularia radiata, Sagittaria platyphylla, Carex alata and a species of Lemna. Along the East Fork of the Trinity River, Jones (pers. comm.) found the species infrequent in a bald cypress swamp associated with Ludwigia sp., Lemna sp., Carex alata, C. hyalina, C. crus-corvi, C. flaccosperma, C. amphibola, C. tribuloides, Cyperus virens, Penstemon tenuis and a species of Hydrocotyle.

Indiana populations of C. decomposita occur in sinkhole ponds rimmed with Cephalanthus occidentalis and/or Populus heterophylla (Homoya pers. comm.). Such habitats are typically less than 0.25 acres in size and draw-down in late August to September. During such periods, however, soils remain moist. Canopy closure varies from relatively open to shaded.

Economic Attributes Not yet assessed
Management Summary
Stewardship Overview: Monitoring should address the threats to habitat caused by water level fluctuations, habitat drainage, and development. Population stability, reproduction, and vigor should all be monitored. Inventory needs include a survey of all potential habitat within the range of the species in order to determine its true status. The species' vulnerability to cold as a range-limiting factor and other basic life-history information (germination requirements, dispersal mechanisms, growth rates, etc.) should be researched. Management needs include the protection of habitat. Constant water levels should be ensured by protecting upstream watersheds.
Restoration Potential: The recovery potential of C. decomposita is probably very good if habitat is maintained or restored. The availability of cypress, buttonbush or tupelo as an anchor cannot be overestimated, and may be a limiting factor in areas possessing otherwise good habitat. Bryson (pers. comm.) observed a population explosion along a reservoir in Mississippi following the cutting of cypress trees. When appropriate habitat is present, large populations typically occur.
Preserve Selection & Design Considerations: Land protection must take into account the entire watershed within which a given population of C. decomposita occurs. Without adequate watershed management, long-term population maintenance is not likely to occur. Protection of existing wetlands and natural cover, as well as restoration efforts should greatly aid this species. Natural, constant water levels should be maintained. At a given site, sufficient buffer should be obtained in order to protect C. decomposita populations from herbicide drift or other factors.
Management Requirements: Habitat protection is the primary management need. Without additional protection, C. decomposita will become increasingly scarce, even in areas where the species is currently widespread and relatively common. Management must not only protect the immediate habitat within which the species is found, but also upstream areas within the watershed. Failure to provide adequate protection to the upstream watershed will lead to more frequent flooding episodes and heightened floodwater elevations. Water level changes of this magnitude could be devastating to existing C. decomposita populations.

Other management needs are currently unknown and should be identified as additional research is initiated and completed.

Protection of existing floodplain habitat and restoration of additional habitat should greatly benefit this species. Upland restoration and protection within the watershed will also increase protection for the species by reducing flood levels.

Monitoring Requirements: A survey of potential habitat throughout the range of C. decomposita is needed in order to determine the true status of the species. Occupied habitats in the south frequently possess cottonmouth, banded water snake and alligators and are consequently, rarely visited.

Monitoring of extant occurrences through time is needed in order to determine population stability and reproductive vigor (Cusick pers. comm.). Such information is important in delineating management problems or identifying areas that need further research.

Additionally, potential threats to habitat should also be monitored (Ludwig pers. comm.). Water levels should be monitored throughout the year in order to determine if excessive fluctuations are occurring. Habitat loss through drainage should also be monitored.

Periodical surveys via individuals counts should be made of selected extant occurrences in order to track population trends. Since plants are largely restricted to Taxodium knees, stumps, logs or the bases of other semi-aquatic tree and shrub species, mapping and marking of existing plants should relatively easy to complete. Reproductive success should also be tracked by visiting the population when seeds have matured. Occasionally, additional checks of nearby potential habitat should be searched in order to identify new plants and note population expansion, if occurring.

The U.S. Fish and Wildlife Service's National Wetlands Inventory is currently mapping existing wetlands throughout the country. Wetland habitat loss through time should be easily tracked after the baseline mapping is complete.

Monitoring Programs: The Illinois Department of Conservation is conducting an annual census of the largest population in the state (Schwegman pers. comm.). Simple counts of the number of plants present are taken and observations of climate, disturbances and flooding which might account for population trends are noted. Contact: John Schwegman, Botany Program Manager, Illinois Department of Conservation, 524 S. Second Street, Springfield, IL 62701-1787. Telephone No. (217) 785-8774.
Management Research Programs: At present, no research is being conducted on any aspect of this species. Periodical inventories, however, are turning up additional populations throughout the range of the species.
Population/Occurrence Delineation Not yet assessed
Population/Occurrence Viability
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
NatureServe Conservation Status Factors Edition Date: 24Oct1990
NatureServe Conservation Status Factors Author: Morse, L.; rev. by W.R. Ostlie (MRO) and S. Gottlieb, rev. K. Gravuer (2010)
Management Information Edition Date: 05Nov1990
Management Information Edition Author: WAYNE OSTLIE
Element Ecology & Life History Edition Date: 05Nov1990
Element Ecology & Life History Author(s): OSTILE, WAYNE

Botanical data developed by NatureServe and its network of natural heritage programs (see Local Programs), The North Carolina Botanical Garden, and other contributors and cooperators (see Sources).

  • Bowles, M.L., et al. 1991. Rarely seen endangered plants, rediscoveries, and species new to Illinois. Erigenia 11:27-51.

  • Bryson, C. T. and S. D. Jones. 1990. Carex comosa new to the state of Mississippi. Sida (in press).

  • Bryson, Charles T. 2002. Preliminary abundance and range estimates for Cyperaceae species of Mississippi. Handwritten notes provided to Mississippi Natural Heritage Program, Jackson, MS. 100 pp.

  • Carter, R., M. W. Morris and C. T. Bryson. 1990. Some rare or otherwise interesting vascular plants from the Delta Region of Mississippi. Castanea 55(1): 40-55.

  • Cochrane, T.S. 2002. Carex Linnaeus section Heleoglochin Dumortier. Pages 278-281 in Flora of North America Editorial Committee (editors), Flora of North America, North of Mexico, Volume 23, Magnoliophyta: Commelinidae (in part): Cyperaceae. Oxford University Press, New York, New York, USA. 608pp + xxiv.

  • Crispin, S. and M. Penskar. 1990. Carex decomposita Muhl. Unpublished abstracts, Michigan Natural Features Inventory, Endangered Species Manual. 3 pp.

  • Cusick, A. W. 1981. Carex decomposita Muhl., cypress-knee sedge. In McCance, R. M. and J. F. Burns (eds.), Ohio Endangered and Threatened Vascular Plants. Ohio Department of Natural Resources, Columbus.

  • Deam, C. C. 1940. Flora of Indiana. Division of Forestry, Dept. of Conservation, Indianapolis, Indiana. 1236 pp.

  • Fernald, M. L. 1941. Another century of additions to the flora of Virginia. Rhodora 43: 485-553, 559-630 and 635-695. (Issued as Contributions from the Gray Herbarium, No. CXXXIX).

  • Fernald, M.L. 1950. Gray's Manual of Botany, 8th ed., Corr. Printing, 1970. Van Nostrand, New York. LXIV+1632 pp.

  • Fernald, M.L. 1950. Gray's manual of botany. 8th edition. D. Van Nostrand, New York. 1632 pp.

  • Flora of North America Editorial Committee. 2002b. Flora of North America north of Mexico. Vol. 23. Magnoliophyta: Commelinidae (in part): Cyperaceae. Oxford Univ. Press, New York. xxiv + 608 pp.


  • Gleason, Henry A. and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York. 910 pp.

  • Godfrey, R.K., and J.W. Wooten. 1979. Aquatic and wetland plants of southeastern United States: Monocotyledons. Univ. Georgia Press, Athens. 712 pp.

  • Guthrie, M. 1989. A floristic and vegetational overview of Reelfoot Lake. J. Tennessee Acad. Sci. 64(3): 113-116.

  • Hermann, F. J. 1941. The genus Carex in Michigan. American Midland Naturalist 25(1):1-72.

  • Hill, S. R. 2006. Conservation Assessment for the Cypress-knee Sedge (Carex decomposita Muhl.). Center for Wildlife and Plant Ecology Technical Report No. 9. Illinois Natural History Survey. Online. Avaliable:

  • Holmgren, Noel. 1998. The Illustrated Companion to Gleason and Cronquist's Manual. Illustrations of the Vascular Plants of Northeastern United States and Adjacent Canada. The New York Botanical Garden, Bronx, New York.

  • Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.

  • Mohlenbrock, R.H. 1959. A floristic study of a southern Illinois swampy area. Ohio J. Sci. 59:89-100.

  • Mohlenbrock, R.H. and J.W. Voigt. 1965. An annotated checklist of vascular plants of the Southern Illinois University Pine Hills field station and environs. Trans. Ill. State Acad. Sci. 58:268-301.

  • Mohlenbrock, R.H., G.E. Dillard and T.S. Abney. 1961. A survey of southern Illinois aquatic vascular plants. Ohio J. Sci. 61:262-273.

  • New York Natural Heritage Program. 2010. Biotics database. New York Natural Heritage Program. New York State Department of Environmental Conservation. Albany, NY.

  • Radford, A. E., H. E. Ahles, and C. R. Bell. 1968. Manual of the Vascular Flora of the Carolinas. University of North Carolina Press, Chapel Hill. 1183 pp.

  • Reschke, Carol. 1990. Ecological communities of New York State. New York Natural Heritage Program, New York State Department of Environmental Conservation. Latham, NY. 96 pp. plus xi.

  • Swayne, J. R. and W. M. Bailey. 1953. New southern Illinois plant records. Am. Midl. Nat. 50(2): 509.

  • Swayne, J.R. and W.M. Bailey. 1953. New southern Illinois plant records. Amer. Midl. Nat. 50:509.

  • Tyrell, L. E. 1987a. The rediscovery of Carex decomposita in Ohio. Bartonia 53: 15-16.

  • Tyrell, L. E. 1987b. A floristic survey of buttonbush swamps in Gahanna Woods State Nature Preserve, Franklin County, Ohio. Mich. Bot. 26: 29-35.

  • Weakley, A.S. 2006. Flora of the Carolinas, Virginia, and Georgia. Working draft of January 17, 2006. University of North Carolina, Chapel Hill, NC. 1026pp. Currently published by the author and available on the web at (

  • Weldy, T. and D. Werier. 2010. New York flora atlas. [S.M. Landry, K.N. Campbell, and L.D. Mabe (original application development), Florida Center for Community Design and Research University of South Florida]. New York Flora Association, Albany, New York

  • Zaremba, Robert E. 1991. Corrections to phenology list of April 9, 1991.

Use Guidelines & Citation

Use Guidelines and Citation

The Small Print: Trademark, Copyright, Citation Guidelines, Restrictions on Use, and Information Disclaimer.

Note: All species and ecological community data presented in NatureServe Explorer at were updated to be current with NatureServe's central databases as of March 2019.
Note: This report was printed on

Trademark Notice: "NatureServe", NatureServe Explorer, The NatureServe logo, and all other names of NatureServe programs referenced herein are trademarks of NatureServe. Any other product or company names mentioned herein are the trademarks of their respective owners.

Copyright Notice: Copyright © 2019 NatureServe, 2511 Richmond (Jefferson Davis) Highway, Suite 930, Arlington, VA 22202, U.S.A. All Rights Reserved. Each document delivered from this server or web site may contain other proprietary notices and copyright information relating to that document. The following citation should be used in any published materials which reference the web site.

Citation for data on website including State Distribution, Watershed, and Reptile Range maps:
NatureServe. 2019. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available (Accessed:

Citation for Bird Range Maps of North America:
Ridgely, R.S., T.F. Allnutt, T. Brooks, D.K. McNicol, D.W. Mehlman, B.E. Young, and J.R. Zook. 2003. Digital Distribution Maps of the Birds of the Western Hemisphere, version 1.0. NatureServe, Arlington, Virginia, USA.

Acknowledgement Statement for Bird Range Maps of North America:
"Data provided by NatureServe in collaboration with Robert Ridgely, James Zook, The Nature Conservancy - Migratory Bird Program, Conservation International - CABS, World Wildlife Fund - US, and Environment Canada - WILDSPACE."

Citation for Mammal Range Maps of North America:
Patterson, B.D., G. Ceballos, W. Sechrest, M.F. Tognelli, T. Brooks, L. Luna, P. Ortega, I. Salazar, and B.E. Young. 2003. Digital Distribution Maps of the Mammals of the Western Hemisphere, version 1.0. NatureServe, Arlington, Virginia, USA.

Acknowledgement Statement for Mammal Range Maps of North America:
"Data provided by NatureServe in collaboration with Bruce Patterson, Wes Sechrest, Marcelo Tognelli, Gerardo Ceballos, The Nature Conservancy-Migratory Bird Program, Conservation International-CABS, World Wildlife Fund-US, and Environment Canada-WILDSPACE."

Citation for Amphibian Range Maps of the Western Hemisphere:
IUCN, Conservation International, and NatureServe. 2004. Global Amphibian Assessment. IUCN, Conservation International, and NatureServe, Washington, DC and Arlington, Virginia, USA.

Acknowledgement Statement for Amphibian Range Maps of the Western Hemisphere:
"Data developed as part of the Global Amphibian Assessment and provided by IUCN-World Conservation Union, Conservation International and NatureServe."

NOTE: Full metadata for the Bird Range Maps of North America is available at:

Full metadata for the Mammal Range Maps of North America is available at:

Restrictions on Use: Permission to use, copy and distribute documents delivered from this server is hereby granted under the following conditions:
  1. The above copyright notice must appear in all copies;
  2. Any use of the documents available from this server must be for informational purposes only and in no instance for commercial purposes;
  3. Some data may be downloaded to files and altered in format for analytical purposes, however the data should still be referenced using the citation above;
  4. No graphics available from this server can be used, copied or distributed separate from the accompanying text. Any rights not expressly granted herein are reserved by NatureServe. Nothing contained herein shall be construed as conferring by implication, estoppel, or otherwise any license or right under any trademark of NatureServe. No trademark owned by NatureServe may be used in advertising or promotion pertaining to the distribution of documents delivered from this server without specific advance permission from NatureServe. Except as expressly provided above, nothing contained herein shall be construed as conferring any license or right under any NatureServe copyright.
Information Warranty Disclaimer: All documents and related graphics provided by this server and any other documents which are referenced by or linked to this server are provided "as is" without warranty as to the currentness, completeness, or accuracy of any specific data. NatureServe hereby disclaims all warranties and conditions with regard to any documents provided by this server or any other documents which are referenced by or linked to this server, including but not limited to all implied warranties and conditions of merchantibility, fitness for a particular purpose, and non-infringement. NatureServe makes no representations about the suitability of the information delivered from this server or any other documents that are referenced to or linked to this server. In no event shall NatureServe be liable for any special, indirect, incidental, consequential damages, or for damages of any kind arising out of or in connection with the use or performance of information contained in any documents provided by this server or in any other documents which are referenced by or linked to this server, under any theory of liability used. NatureServe may update or make changes to the documents provided by this server at any time without notice; however, NatureServe makes no commitment to update the information contained herein. Since the data in the central databases are continually being updated, it is advisable to refresh data retrieved at least once a year after its receipt. The data provided is for planning, assessment, and informational purposes. Site specific projects or activities should be reviewed for potential environmental impacts with appropriate regulatory agencies. If ground-disturbing activities are proposed on a site, the appropriate state natural heritage program(s) or conservation data center can be contacted for a site-specific review of the project area (see Visit Local Programs).

Feedback Request: NatureServe encourages users to let us know of any errors or significant omissions that you find in the data through (see Contact Us). Your comments will be very valuable in improving the overall quality of our databases for the benefit of all users.