On peat and humus-rich soil, at the base of living trees with a mossy acidic bark, on rotting logs, and over natural, siliceous and sandstone outcrops, also common in disused quarries.

Two chemotypes with minor morphological differences have been recognized in the study area:

var. squamosa:

Belgium: Camp.: R, Mosan: R, Ard.: AR, Lorr.: RR.

Luxembourg: Ard.: AR, Lorr.: AR.

France: Ard.: R, Lorr.: RRR.

var. subsquamosa (Leight.) Vain. [syn.: C. subsquamosa (Leight.) Cromb., nom. illeg.]:

Belgium: Ard.: RR.

Luxembourg: Ard.: RRR, Lorr.: AR.

France: Lorr.: RRR.

Lit.: La68: 76, La69: 135, Mü1: 148, Mü2: 195, Diederich (1985b: 31).