Grass Vetchling (Lathyrus nissolia)
The plant of Grass Vetchling is almost indistinguishable from common grass varieties until its perfect, small, pea shaped flowers emerge for a short time in June and July. It is this resemblance to a grass that gives it its name, Grass Vetchling.
There are a couple of other places in Purbeck where they occur, on the cliffs around Kimmeridge Bay is one. I am not sure if it occurs outside Purbeck but would not be surprised to find it on Portland.
A lovely little gem, hard to find but well worth the effort.