Carex vesicaria

Taxonomy 

Carex vesicaria L., Bladder Sedge, has no synonyms.

The American name for it seems to be Blister Sedge.

Chromosome No.: 2n = 74, 82 (Stace 2010).

Carex vesicaria

Photography A.J.Lockton

Identification 

The biggest problem is distinguishing it from Bottle Sedge C. rostrata. They are quite similar in height and fruiting spikes; they grow in similar habitat; and they both form extensive, rhizomatous, swamps. Sometimes they even grow together.

Differences include:

  • C. vesicaria is yellowish in colour while C. rostrata is glaucous.
  • C. vesicaria has stomata on the lower surface of the leaves (upper surface in C. rostrata).
  • Utricles in rostrata have a bottle-shaped beak; more gradually tapering in vesicaria.
  • A useful jizz feature: swamps of vesicaria rustle in the wind.
Distribution 

Widespread throughout the British Isles, but absent from the Northern Isles and very rare in the Outer Hebrides. GBIF shows it as frequent throughout Europe and North America with scattered localities in other parts of the world.

BSBI Hectad Map 

Click on the map to view full-size on the BSBI Maps Scheme website.

Status 
  • Origin: native throughout the British Isles. The first British record is given as 1699 in Clarke (1900).
  • Rarity: common and widespread.
  • Threat: in the New Atlas it is given a Change Index of -0.52, which is quite a severe decline. Cheffings & Farrell (2005) list it as Least Concern.
  • Conservation: for such a widespread plant, C. vesicaria is usually popular with county recorders, as most list it as an axiophyte. It is a useful indicator of swamps, wet meadows and some of the more base-rich mires.
Ecology 

The most obvious vegetation community is S11 - C. vesicaria swamp, but it is easy to make the mistake of thinking that all stands of C. vesicaria are this community. Rodwell (1991-2000) also allows it as a constituent of OV30, S27, M27. It grows in places where there is a high water table, possibly fluctuating slightly, but rarely completely inundated. Substrates include mineral soils and peat, but it does not grow on ombrotrophic mires. Its light requirement is high (Ellenberg L value of 8, according to Hill et al., 1999), but it would presumably only tolerate light grazing.

Further Work 

One curious feature of C. vesicaria is the distribution of its hybrids. The cross with C. rostrata grows in several places in Shetland, well beyond the range of C. vesicaria. Does that mean it was formerly present in Shetland, or is the hybrid - which is thought to have low fertility - able to disperse long distances itself? Other hybrids, between this and other common species, are surprisingly rare - possibly overlooked.

Here are the maps of its various crosses:-

If anyone would like to research these hybrids in more detail, and maybe even provide us photographs of them, it could prove very worthwhile. Further details are available in the new Sedges Handbook. The ecology of C. vesicaria would also be worthy of further studies, particularly to find out the extent of the apparent decline within its range, and the habitats that are seemingly being lost.

Citation 
Lockton, A.J. (Date accessed). Species account: Carex vesicaria. Botanical Society of the British Isles, www.bsbi.org.uk.

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