Isoetes histrix

Range & Status

Native; a Mediterranean-Atlantic plant found in Cornwall and the Channel Islands.

Regional Distribution

In Cornwall it occurs only on The Lizard. Since 1950 it has been recorded in a total of 21 1km squares at 71 sites. Population numbers at these sites were investigated in spring 1982 (Frost et al ., 1982) and though some populations were small, many were in the hundreds, and at one site 70,000 were estimated. Since 1999 it has only been recorded in six 1km squares at 16 sites. However, there is no reason to doubt that plants are still present at the remaining old sites as population numbers fluctuate more due to weather conditions than tourist pressure.

Habitat & Ecology

It grows in moist, maritime turf, in shallow coastal erosion pans that are stony with serpentine fragments, or on moist tracks where trampling and shallow soils around the serpentine outcrops keep the vegetation open. Sites favoured most are those where water stands in winter.


Populations can be reduced where scrub vegetation encroaches on sites around serpentine outcrops. There is little tourist pressure as the plants are generally invisible above ground from June to October.


Rough grazing helps to maintain the species, and recent clearance work by the National Trust has opened up previously scrub-covered outcrops. All the sites are SSSI.