It was first recorded in 1837 by botanist Thomas Edmondston, who was 12 at the time.

For a long time it was synonymised with arctic mouse-ear Cerastium arcticum but it is now widely regarded as a separate species.

[citation needed] Although reported from two other sites in the 19th century, it currently grows only on two serpentine hills on the island of Unst (see Keen of Hamar).

The numbers of Cerastium nigrescens can vary dramatically from year to year, for reasons that are unclear (probably due to a varying rates of seedling germination and survival), but the underlying trend seems stable, and there has been no change in its distribution.

Flowers look disproportionately large compared with the size of the plant.