Carex aggregata Rediscovered in New York

By Steve Young, NY Natural Heritage Program

In 2008 Heather Liljengren and Camille Joseph, staff members of the Greenbelt Native Plant Center in Staten Island, were collecting graminoids for seed preservation in Inwood Hill Park on the northern tip of Manhattan Island during the last week of May. They noticed a sedge that looked different and collected it to send off to Dr. Rob Naczi, a sedge expert at the New York Botanical Garden, for identification. Dr. Naczi confirmed it as glomerate sedge. Then in June 2009 Rob Naczi himself discovered it in the southwestern portion of the botanical garden grounds near the Bronx River during a survey of the plants of the Bronx Forest. Both of these discoveries were then reported to the Natural Heritage Program in 2011.

Only three populations of glomerate sedge have ever been reported from New York (there is also a Torrey specimen at NYBG with no location) which is at the northeastern edge of its range. It was first collected from the Perch Lake area of Jefferson County in 1949 then again in 1959 from the Spring Valley area of Rockland County. In 1988 Mike Oldham, a Heritage botanist from Ontario, collected it in Oakwood Cemetery during a trip to the Natural Areas conference in Syracuse. Another trip to the cemetery site in 1990 did not find the plants again. All of these collections occurred during the last week of May or in June. For 20 years there were no more collections or sightings of this sedge in New York until that day in Inwood Park.  This sedge now has the distinction of being the only state endangered or threatened plant that currently exists on Manhattan Island.

From the New York Natural Heritage Program conservation guides we have the following information about identifying this sedge: There are three other members of Carex section Phaestoglochin (C. sparganioides, C. cephaloidea, and C. gravida) that are similar.
Carex sparganioides is perhaps the most different from C. aggregata of these three. It has a more elongated inflorescences (3-15 cm long) with a larger proximal internode. In addition the widest leaf blades are 5-10 mm wide (Ball 2002).

Carex cephaloidea is the most similar to C. aggregata of the species that occur in New York. Carex cephaloidea has the widest leaf blades (4-)5-8 mm wide and the ligules are just longer than wide. In addition, the pistillate scales are 1.5-2 mm long, subobtuse to acute, and the bodies are no more than 0.5 times the length of the perigynia. Mackenzie in his description of C. aggregata (as C. agglomerata) used culm scabrousity to separate C. cephaloidea and C. aggregata. The angles of the culms of Carex cephaloidea being strongly serrulate while those of C. aggregata are only roughened just below the inflorescence. These character states may be incorrect or subtle.

Carex gravida does not occur in NY but was attributed to the state incorrectly in the past. It is not expected in the state. Carex gravida mainly differs in having the summit of the leaf sheath fronts white, hyaline, not thickened, and fragile.

Carex aggregata illustration from Britton and Brown 1913.

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