This erect, hairless species grows in fresh-water marshes, on ground which is flooded and wet and close to ponds. It grows to a height of about 60cm and, as the name might suggest, its stems are hollow and soft. These stems are inflated between the nodes. The flowerheads are in the typical umbel shape of the Apiaceae or Carrot family, to which this species belongs, with two to four rays, 1-3cm long. There are no bracts.The flowers are pale pink and in small, domed, secondary umbels. The leaves are once or twice pinnate, with the upper leaflets linear and untoothed and the lower leaflets small and wedge-shaped. The fruit is in spiny, round balls. Tubular Water-dropwort is a native perennial and it flowers from July to September.
I first saw this species in 2017 near Ballinesker in County Wexford after taking an excellent workshop on the Apiaceae family given at the National Biodiversity Data Centre in Waterford by Paul Green, BSBI Vice-County Recorder for Wexford and Waterford.
If you are satisfied you have correctly identified this plant, please submit your sighting to the National Biodiversity Data Centre