The plants typically flower from May to July and set seed in July and August. They avoid drought by growing in winter and flowering in early summer when there is usually enough moisture available. However, a wet summer can change this pattern. The seed can lie dormant for many years and it is possible that disturbance of the soil on former known sites may encourage germination.
Widespread in southern Europe, it is known from only five established sites in Britain, the north-westernmost part of its range. These are in Kent, Sussex, Somerset and Oxfordshire. It is only in these sites where hot conditions in summer allow it to survive.
Rough marsh mallow is one of a group of plants that prefer a 'Mediterranean' type of climate. They like open, shallow soils which are baked dry by hot summer sun. This plant's habit of early flowering and winter growth has limited its range in the UK to sun-warmed slopes. Ideally, rabbit activity should provide suitable conditions by limiting competition and producing scrapes and small scale disturbance, and the site should be dried out over the summer months.
The rough marsh mallow has declined largely through habitat loss. Much suitable habitat has been lost to agricultural improvement or succession to scrub as a result of neglect or lack of rabbit grazing. When rabbit populations are reduced by periodic outbreaks of myxomatosis, or excluded by the erection of a rabbit-proof fence, the mallow is likely to disappear from a site.
The rough marsh mallow is listed on Schedule 8 of the Wildlife and Countryside Act 1981, which means it is a protected species within the UK. Because of the rarity of the rough marsh mallow, it was included in English Nature's Species Recovery Programme. In partnership with Plantlife's 'Back from the Brink' project, this has sought to reverse the decline of the plant.
The work of recovery has hinged on long-term monitoring and management as well as restoring suitable habitat, for example, by scrub control. Part of the work has also focussed on involving the local community and landowners in conservation work for this species. One method used has been the rotovation of plots where the mallow has been known to grow in the past, in order to provide the right conditions to allow germination of any remaining seed. Rough marsh mallow sometimes occurs in company with other rare species that need similar conditions such as nit grass and ground pine.
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