The shallow soils of a South East Water covered reservoir near Eastbourne are providing the ideal growing conditions for one of the UK’s rarest plants, the hairy (or rough) mallow (Althaea hirsuta).
Since 1984, when the species was first identified at the site, plant numbers have fluctuated depending on varying weather conditions. In 2014 South Downs National Park Volunteer Rangers counted almost 250,000 plants but the following summer there were none. This year there are approximately 37,000 plants.
Dr Patrick Austin, Environment Officer at South East Water, said, “This confirms that the site remains a stronghold for this species in the United Kingdom and that management plans implemented by South East Water to ensure the conservation of the species are proving to be successful.”
Hairy mallow is more commonly found in the Mediterranean and south west Asia. It was first discovered in Britain in 1792 at Cuxton in Kent where it still appears alongside other rare species. Dr Austin said: “It is clear that here in Britain the species is at the northern edge of its range and is reliably found at just a handful of sites.”
The plant thrives in open, disturbed conditions with low levels of competition from other species and generally flowers in mid-June. As a result of its scarcity it is protected under the Wildlife and Countryside Act and it is an offence to intentionally pick, uproot or destroy any plants.
The population at the South East Water site (a Site of Special Scientific Interest since 1987) has been closely monitored since 1994. under the auspices of the Plantlife ‘Back from the Brink’ project.
However, its arrival at the site is a mystery. When the reservoir was constructed it was covered with the same chalk from the excavation and no foreign topsoil was introduced.
One theory is that the seeds, which remain dormant in the seedbank for long periods, may have been transported by birds or the wind from a former chalk pit near Cuckmere Haven where the species was last recorded in 1958.