Butomus umbellatus Flowering-rush

Butomus umbellatus, Flowering Rush, is a rhizomatous aquatic plant which is rather uncommon in Wales. It is a plant of fenland but it is more often found emergent at the edges of canals and ditches and is instantly recognisable when it produse its attractive umbels of pink, insect-pollinated, 3-petalled flowers at the tops of long single stems in summer. Plants are either diploids or triploides. The diploids are self compatible and produce seeds which float on the water and disperse with the currents. Triploids are self-incompatible and rarely produce seeds. However, vegetative reproduction and dispersal can also take place through the detachment of lateral buds that occur on the rhizomes. It has a very local distribution in West Glamorgam with populations in Oxwich marsh, the Tennnat Canal and wetlands near Morfa and the Kenfig river. It was probably widespread in Crymlyn Fen in the past but has not been recorded there for a long time. However, it was able to colonise the Tennant Canal (probably via the Glan y wern Canal which runs through the eastern part of Crymlyn Fen) and it has gradually spread along the canal from Jersey Marine to Neath Abbey, particularly in recent decades. It has not been recorded on the Neath or Swansea Canals and unlike other aquatic plants whose propagules are dispersed by waterfowl, its ability for long distance dispersal appears to be very limited.