Very frequently found growing on the margins of canals, ponds and in other shallow, wet places, this is a semi-aquatic perennial. Growing to 1m high, it's an attractive wildflower which produces white, often-tinged lilac, 3-petalled flowers (1cm across) in whorled panicles from June to August. The petals are softly rounded, with a touch of yellow at their narrowest part, and can best be seen in the afternoon when the flowers usually open, displaying the six stamens. The oval, long-stalked leaves have parallel veins and have a slightly heart-shaped base. This is a native plant which belongs to the family Alismataceae.
My first record of this plant is in 1978 at Newcastle, Co Wicklow. I photographed it beside the Royal Canal, Vicarstown, Co Kildare in 2005.
If you are satisfied you have correctly identified this plant, please submit your sighting to the National Biodiversity Data Centre