Creeping marshwort  (Apium repens)

Classified as Critically Endangered in the UK. Classified as Vulnerable in Europe.

As its name suggests, creeping marshwort is a low-growing plant. The leaves are toothed with a single large cleft, and the plant sends out runners which creep low to the ground or slightly below the surface. At the nodes - where the leaf stalks grow from these runners - the plant puts out rootlets. The flowers are tiny and white, and are carried on umbels - umbrella-like spokes - from which this family of plants gets its name.

This is a difficult plant to identify accurately as there are two varieties of a closely related species, fool's watercress Apium nodiflorum, that strongly resemble it. In fact, some botanists are unsure whether creeping marshwort deserves its status as a distinct species. Hybrids of the two plants have also been recorded.

Creeping marshwort is recorded from several countries in north-west Europe but nowhere does it appear to be common. In the UK it has been found at 10 locations during the 20th century but is now limited to just two sites in Oxfordshire, and another one where it has been re-introduced.

You can view distribution information for this species at the National Biodiversity Network Gateway.

This species requires a wet environment and short, disturbed turf. It has been recorded from wet meadows, ditches and shallow ponds. It seems to benefit from winter flooding, but does not tolerate inundation in summer.

Creeping marshwort is a perennial plant and flowers in July. As well as spreading by its creeping runners it can also reproduce by seed. The plant relies on trampling by cattle to enlarge its territory although this needs to be restricted to avoid compaction of the soil. At the plant's second native site, it reappeared after an absence of 30 years, following the reinstatement of an appropriate grazing regime.

As this species is thought never to have been common, those sites where it is still found, including those in Europe, and those where it has been recorded are continuously monitored to assess the environmental needs of the plant. It is believed that fluctuations in the water levels as well as changing grazing methods may be responsible for changes in population levels as well as increased use of herbicide spraying.

There still remains a question about the true status of creeping marshwort as a separate species, given its resemblance to fool's watercress and the fact that hybrids of the two plants have been found. However, there is definitely strong support for the fact that the species is a true variety and in 1995, English Nature added the plant to its Species Recovery Programme. It is also listed under the UK Biodiversity Action Plans (UKBAPs).

The location in Oxfordshire, where the plant has been monitored, has been declared a candidate Special Area of Conservation site (cSAC), which grants protection under European Law. Re-introductions have been carried out on other suitable sites with mixed success.

Visits to Belgium and the Netherlands where the plant also grows, have established that grazing might not necessarily be a management requirement. At one site, mowing of the sward by volunteers produced a return of creeping marshwort, albeit for just a short period. At another site regular, short mowing has created and maintained a long-term viable population.

Other studies have been made in the field to observe how the species is pollinated and which insects are necessary to carry out this task. This pollination experiment suggested that cross-pollination results in better seed production than if the plant pollinates itself. Experiments are also planned to re-introduce plants to other suitable sites and carefully monitor their progress in order to secure the future of this elusive species.

There may be further information about this species available via the National Biodiversity Network Gateway.

The UK Biodiversity Action Plan for this species is available at UK BAP.