The genus Callitriche (water-starworts), is poorly understood, widely mis-identified and under-recorded throughout the world. It includes fewer than 100 species but these occur on every continent except Antarctica, although C. antarctica occurs in southern South America and the peri-antarctic islands. The aim of the project is to review the literature, unpublished data and herbarium specimens to establish exactly how many species are in the genus worldwide and to assess their conservation needs.

 To achieve this, herbarium specimens have been borrowed from institutions around the world on loan to the Herbarium of the Royal Botanic Gardens Kew and two field surveys have been undertaken. The first field survey was to the islands of Sardinia and Sicily in the Mediterranean where we were able to reinstate an overlooked water-starwort and revise the distribution of two other species. The second field survey was to South Africa where there has always been confusion pver the true number of native species and we were able to show that there is only one native species; C.compressa as well as a non-native which is spreading out into the wild from Garden Centres.

The review of herbarium specimens has shown that many species are known from only one or two specimens - so poorly known that their conservation needs cannot be understood and that there may be as many as 10 new species to science represented in herbaria but un-recognised.

IUCN Red List Assessments are being prepared for each of the worlds species and this forms the basis of the Genus Conservation Strategy, the results of the field surveys are being published and a major taxonomic revision of the genus is being prepared with plans to describe the new species.