The status of this species in Northern Ireland is uncertain, but the only sites where it has any possibility of being a native are those around Crossgar (where it became extinct) and Downpatrick.
It is now confined within Northern Ireland to the Hollymount Nature Reserve near Downpatrick and the Downpatrick marshes nearby. It grows in deep drains, totally submerged apart from the flower spike.
The plant was deliberately introduced into the Bog Meadows near Belfast and to Whinnigan Glebe townland in Co. Fermanagh, but it is long extinct at both sites.
All names: Hottonia palustris L.
NBN Atlas mapping: Species account : NBN Atlas UK Species Observations database
iNaturalist: Species account : iNaturalist World Species Observations database