Draba muralis Wall Whitlowgrass R DD N
This is one of those names which confuses because Wall Whitlowgrass is not one of the usual Whitlowgrasses nor is it a grass. It is however one of the many early flowering white crucifers sent to confuse botanists. In the same place as this plant were growing Erophila verna (Whitlow grass), Cardamine hirsuta (Hairy Bittercress), Arabidopsis thaliana (Thale cress) and Saxifraga tridactylites (Rue-leaved Saxifrage) - all have small white flowers. D. muralis is quite a leafy plant and thankfully produces fruit (seeds) quite quickly after flowering these are distinctly different from any of the other plants except Erophila verna which is small and has no leaves on the stem and actually looks nothing like it.
This is not an easy plant to find though. It grows on limestone near rocky outcrops which, I find, are usually through a thicket and up a scree slope with no obvious route.
D. muralis is dotted about in the British Isles and Ireland without there being much of a concentration anywhere.