Stonecrops grow in dry places; they especially favour rocks and walls and, indeed, some members of the family are popular plants in garden rockeries. Mossy stonecrop (Crassula tillaea), however, grows and bare sandy patches of soil on heathland. It can occasionally be found growing on the bare, well trodden and baked ground of footpaths where nothing else can grow as it is too weak to tolerate any completion for resources.
Mossy stonecrop does actually look like a moss so it is well named. A tiny, prostrate and spreading out across the ground from its central root it forms something of a mat on the ground, much like some species of mosses can do. The whole plant is red in colour and it gives the appearance of being dead and shrivelled up even when in full flower! The flowers are very small and not really discernible without magnification.
Originally a plant of Mediterranean climates it was once quite rare here in Britain but it seems to be spreading and can be found in car parks (non-tarmaced ones of course) and on caravan sites. Away from artificial sites like these the Dorset heaths are a likely place to find it.