Clavularia crassa forms small colonies of up to about fifty individual polyps growing from a stolon.

[2] Clavularia crassa is found in the Mediterranean Sea and the proximate areas of the eastern Atlantic Ocean, the coasts of Portugal and Algeria.

It occurs in positions with moderate to high movement of water and its depth range is from about 1 to 33 metres (3 to 100 ft).

[2] This octocoral is often to be found growing on the rhizomes of the seagrass known as Neptune grass (Posidonia oceanica), as well as on algae and sponges.

From late June onwards, eggs are extruded through the mouths of the polyps and remain stuck together in small orange clusters.