Also known as: sea isle sedge, invasive sand sedge
History & Introduction
Originally from East Asia, Carex kobomugi was introduced accidentally to the U.S. in the early to mid-1900’s, possibly arriving through ballast water. Growing readily in coastal ecosystems, the plant was promoted for erosion control to stabilize dunes, and planted over the east coast. Populations now extend across the coast from Massachusetts to North Carolina. After Hurricane Sandy in 2012, fragments of the plants from New Jersey washed up on New York shores, allowing the plant to establish numerous populations in the Rockaways and Fire Island. It is a prohibited plant in Connecticut, but not yet on the regulated species list in New York.
Identification & Biology
C. kobomugi is a sedge characterized by its V-shaped leaves that are triangular in cross section. Its leaves have a yellow-green color (compared to native beach grasses that have a bluish-green appearance). C. kobomugi is relatively short, reaching 15-30 cm (6-12 inches). They have small teeth along the edge of the leaf that can be felt or seen with magnification. Flowering and fruiting occurs April through June, as the plant sends up a short brown spike of either male or female flowers (dioecious). While their seeds are salt-tolerant and able to float, they reproduce primarily through vegetative spread. They can form dense colonies via their underground stems, or rhizomes. Rhizome fragments transported over water can establish new colonies.
Lookalikes:
Damage & Concern
Growing to densities of up to 350 shoots per square meter, populations of C. kobomugi can outcompete native beach grasses and forbs. This can include American beach grass (Ammophila breviligulata), and seabeach amaranth (Amaranthus pumilus) – a state and globally imperiled species. Their populations can reduce the habitat available for the threatened piping plover (Charadrius melodus). While the plant does achieve the function of stabilizing dunes, native dune species are argued to stabilize dunes just as well.
Management
Managing C. Kobomugi can be a balancing act between removing harmful invasive species while maintaining native plant populations and stable dunes. In any chosen management technique, limit the off-target impacts to maintain the ecosystem services that dunes provide.
Strategy: (Adapted from Wootton et al. 2005)
- Remove small colonies of C. kobomugi where it threatens a particularly biodiverse area, or areas with rare native species.
- Survey for new populations of C. kobomuji, to enable the rapid successful control of emerging stands.
Manual/Physical:
- Manual control can be difficult as pulling can leave underground stems behind. This is a good option for small, emerging colonies. Repeat manual control will be necessary; mapping locations of control can aid in follow-up removals.
- Burying C. kobomugi under sand has been attempted as a management method, however researchers have found that C. kobomugi is better at emerging through burial depths of 18 inches compared to native species. Repeated burial would be necessary.
Chemical:
- Glyphosate formulations can be used to control C. kobomugi, at a rate of 2-3%, with repeat treatments in a season recommended. This can be performed with selective spot treatments, in order to minimize the exposure of surrounding native plants. Intensive broadcast spray applications can cause widespread plant defoliation, putting the stability of the dune at risk.
- Always follow the instructions on the pesticide label.
Monitoring & Reporting
LIISMA is currently monitoring C. kobomugi; as reports of the species are collected, LIISMA is dedicated to containing early emerging infestations of the species before they become widespread. C. kobomugi is currently a Tier 3 species on Long Island.
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Citations
https://www.invasive.org/alien/fact/cako1.htm
https://www.cabidigitallibrary.org/doi/10.1079/cabicompendium.112985
https://www.lhprism.org/species/carex-kobomugi
Wootton, L.S., Halsey, S.D., Bevaart, K. et al. (2005) When Invasive Species have Benefits as well as Costs: Managing Carex kobomugi (Asiatic sand sedge) in New Jersey’s Coastal Dunes. Biol Invasions 7, 1017–1027. https://doi.org/10.1007/s10530-004-3124-y
