Vascular Plants of North Carolina
Account for Bladder Sedge - Carex intumescens   Rudge
Members of Cyperaceae:
Members of Carex with account distribution info or public map:
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Section 5 » Order Cyperales » Family Cyperaceae
AuthorRudge
DistributionThroughout the state; rare on the Outer Banks. Note that now (2021) there are 2 varieties in NC.

N.S. to WI south to central FL and eastern TX.
AbundanceFrequent to common throughout the state, except scarce on coastal islands.
HabitatFloodplain forests, bottomlands, montane seepages, bogs, fens, margins of beaver ponds.
See also Habitat Account for General Sedge, Grass, and Rush Mires
PhenologyFlowering and fruiting May-July.
IdentificationCarex intumescens looks very similar to C. grayi, but the heads are not as round (more often obovoid or ovoid) and have fewer perigynia (1-12 vs. 8-35 in C. grayi). Both occur in bottomland forests across much of the state, though the latter species has a more restricted NC range (and is not in the Mountains).
Taxonomic CommentsMedford et al. (2021) recognized var. fernaldii L.H. Bailey, which in NC occurs in high elevation spruce-fir and northern hardwood forests. A previous paper (1974, Canadian Journal of Botany, p. 2387) dismissed this variety, but Medford et al. seem convincing.

The genus Carex is the largest in North America, and among the largest in the world. In temperate and boreal regions, Carex is often the dominant or co-dominant ground layer in many habitats. Seeds (achenes) are valuable food for birds and small mammals, while foliage is used by birds and mammals to make nests and as food by mammals. Species of Carex often look vastly different from one another -- spikes erect vs. drooping, tiny inflorescence vs. whopping, culms leafy vs. naked, perigynia beaked vs. beakless, stems densely bunched vs. single, etc. The genus has been divided into many sections (or groups), based on shared characters; some taxonomists have suggested that these be different genera, but that proves unworkable (so far). All Carex share the feature of a perigynium (an outer covering) which completely surrounds the achene (seed). This covering may fit tightly or loosely (like a small bladder), depending on which group or species. Details of perigynia shape, ornamentation, presence and size of beak, number of striations (or veins) are all important ID features. In recent years Rob Naczi and colleagues have stressed the importance of arrangement of perigynia -- whether spiral (3+ ranks) or distichous (2-ranked) -- and have named a number of new species as well as split off some older synonyms. Therefore, RAB's (1968) key, excellent for its time, can only be used in a general way today. Members of some sections of Carex are difficult to key out (notably Ovales, Laxiflorae, Griseae); this is in part due to variation among individuals of a species, or failings of the key. FNA has drawings of most species and some species may be found in two or more places within a key, to acount for variability. New species to NC, and new to science(!), continue to be found in NC.
Other Common Name(s)Greater Bladder Sedge
State RankS5
Global RankG5
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