lesser pond sedge; European lake sedge

Ottawa, Canda. (Catling 2005)

Tall Carex species, such as C. acutiformis, may dominate fens that are rainwater fed and base-poor relative to short Carex species, which tend to dominate base-rich fens (Verhoeven and Arts 1992). In acidic waters (e.g., base-poor fens), the decomposition of cellulose in C. acutiformus plant matter may occur slowly, preventing the full release of nutrients until 3-4 years after death and immobilizing N and P for a longer period of time relative to other sedges (Aerts and de Caluwe 1997, Verhoeven and Arts 1992). However, because C. acutiformis produces more leaf litter than most sedges, it may actually facilitate a higher rate of nutrient cycling than what the other sedges attain (Aerts and de Caluwe 1997).

Germination occurs at temperatures above 15°C, peak emergence is in early summer, and fruiting occurs June–August (Schütz 1998). Percent emergence (from seed) is very low at shaded sites, possibly due to a relatively high minimum temperature requirement. In European populations, the production of viable seed in C. acutiformis is low relative to that of other sedges, suggesting that clonal reproduction is favored (Schütz 1998).

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental

Carex acutiformis has a moderate environmental impact in the Great Lakes.
Realized:
Currently, there are few reported populations of C. acutiformis in the Great Lakes, suggesting that it is a relatively rare introduction. However, the swamp sedge is often misidentified as the native water sedge (C. aquatilis), which could limit its documentation. It does not appear to disperse well across long distances, but where it establishes, it is capable of spreading locally via rhizomes and displacing native species (A. Reznicek, pers. comm.). In 1982, C. acutiformis was observed forming a near monoculture around the entirety of St. Joseph Lake, South Bend, IN. Similarly, C. acutiformis was discovered dominating a 6-acre open marsh area in the Stony Swamp Conservation Area near Ottawa, ON. In this conservation area, C. acutiformis co-existed with native trees but had displaced nearly all other native plants in both open water and some relatively dry areas (Catling and Kostiuk 2003). Thus, this species may be a very serious threat to native vegetation on a local geographic scale due to its ability to spread rapidly via vegetative growth and out-compete native species for nutrients and light (Catling and Kostiuk 2003; A. Reznicek, pers. comm.) It may also smother native plants via accumulation of its excess litter (Catling and Kostiuk 2003).

Carex acutiformis has been found to have a longer lifespan and create more above ground plant biomass than three of the native sedge species: C. diandra, C. rostrata, and C. lasiocarpa (Aerts and Caluwe 1995, Konings et al. 1989).  Carex acutiformis was also the most efficient  in nitrogen use relative to production of biomass (Konings et al. 1992).

Potential:
As of 1992, a total of 253 Carex hybrids have been reported in North America. This indicates that this genus is highly capable of hybridization, and invasive species, such as C. acutiformis, may be a genetic threat to native sedge species (Cayouette and Catling 1992).

There is little or no evidence to support that Carex acutiformis has significant socio-economic impacts in the Great Lakes.

There is little or no evidence to support that Carex acutiformis has significant beneficial effects in the Great Lakes.
Potential:
Carex acutiformis has been used in horizontal subsurface-flow constructed wetlands in Denmark, Slovenia, and Germany (Vymazal 2011). Carex acutiformis (in combination with Spartina pectinata and Phragmites australis) was successful in removing 91.6% of the ammonium concentration and 80.6% of organic nitrogen in a treatment wetland in Germany, which was developed to treat dairy farm wastewater (Vymazal and Kröpfelová 2008).

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Control
Biological
There are no known biological control methods for this species.

Physical
Harvesting, either mechanically or by hand, may be a viable option, depending on site conditions. Extreme care should be taken to remove all parts of the roots system and rhizomes to prevent further spread of the species. This method is unlikely to eradicate swamp sedge, but it will help to prevent population expansion. Physical control methods are most effective when completed before seed production (USACE 2011b).
Seeds do not germinate when they are 7 cm below the soil surface (Schütz 1998). Thus, tilling the soil to push the existing seeds deeper into the substrate may be an effective method for reducing the prevalence of swamp sedge (Curran et al. 2009).

Carex acutiformis does not extend into open water deeper than 55 cm, and it able to cope with low water levels. Stands of C. acutiformis did not decrease immediately after moderate reduction in water level, suggesting that water level alteration may not be an effective form of control (Lawniczak et al. 2010).

Chemical
Currently no peer-reviewed literature examines the efficacy of herbicides against swamp sedge. According to the Center for Ecology and Hydrology all sedges are susceptible to glyphosate; an application in mid to late summer will maximize translocation and control of rhizomes (USACE 2011a). Imazapyr has also been effective in controlling some sedge species (USACE 2011a).

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.