American Willowherb grows to about 75cm high. It bears 8-10mm pink flowers on upright, reddish stems from June to September. These flowers have 4 deeply-notched petals, club-shaped stigmas and a calyx tube which is barely hairy. The stems have 4 raised lines along them and spreading glandular hairs. The lanceolate-oval leaves are short-stalked, opposite, hairless and loosely toothed. This plant seems to favour disturbed ground, gardens, roadsides and damp woodland. It has no stolons. It is an introduced perennial which is widespread in the East and South. It belongs to the Onagraceae or Willowherb family.
I first saw and photographed this species in Gibletstown, Co Wexford in 2013.
If you are satisfied you have correctly identified this plant, please submit your sighting to the National Biodiversity Data Centre