The species was once abundant on the Isle of Man, hence its name, however, for an unknown reason its population has collapsed to only a few individual and isolated plants.

[2] The plant prefers light (sandy), medium (loamy) and heavy (clay) soils, which must be well-drained yet moist.

The plant can grow in acidic, neutral and alkaline soils, in semi-shade (light woodland) or no shade.

Trampling by walkers can help achieve this habitat, hence C. m. monensis can often be found growing along footpaths through coastal dunes.

It may have been introduced to the U.S. as the Isle-of Man cabbage and subsequently evolved through the founder effect and geographic isolation into a new subspecies.