This is an upright perennial which grows on marshes and by rivers, on rocks and waste ground. It has pink flowers (6-8mm across) with 4 notched petals and a distinct club-shaped stigma and they bloom in July and August. It has a branched stem with ridges running down from the base of each leaf. The leaves are unstalked, mostly opposite, toothed and oval-lanceolate. The pods containing the cottony seeds are 4-6cm long. This is a native wildflower and it belongs to the family Onagraceae.
I first identified this plant in Gibletstown, Co Wexford in 2008 at which time I also photographed it.
If you are satisfied you have correctly identified this plant, please submit your sighting to the National Biodiversity Data Centre