Not to be semantically confused with : Wall-rue (Asplenium ruta-muraria), Wall-Rocket (Diplotaxis tenuifolia),
Wall Whitlowgrass (Draba muralis),
Wall Bedstraw (Galium parisiense),
Wall Barley (Hordeum murinum), Wall Lettuce (Mycelis muralis), Pellitory-of-the-Wall (Parietaria judaica),
Wall Germander (Teucrium chamaedrys), Wall Pennywort (Umbilicus rupestris), Wall Speedwell (Veronica arvensis) nor with
Wallaby-grass (Rytidosperma racemosum) [plants with similar names belonging to some differing families (and others the same Brassicaceae)]
Easily mistaken for 3 other Erysimums :
Treacle Mustard (Erysimum cheiranhoides) which is an erect annual growing to 60cm (up to 1m) high with elliptical lower leaves which are either toothless or shallowly toothed and small hairy-on-the-underside yellow petals just 3 to 6mm long.
Siberian Wallflower (
Erysimum × marshallii) which is usually biennial and growing erect to 50cm with with stems which are frequently branched lower down and leaves which are narrow-elliptical with teeth only near the ends - which is also grown extensively in gardens but which does not naturalise in the wild - although it may be found thrown away on tips etc.
The third Erysium is Spreading Treacle-mustard (Erysimum repandum) a well-branched annual growing erect to 50cm with yellow petals between 6 and 10mm long. It has lower leaves which are lanceolate and often shallowly to deeply lobed but this is now much less common than was.
Like most Brassicaceae the species in Ersimum produce toxic Glucosinolates for defence but they additionally also produce
cardiac glycoside which are also used by the plant for defence against insects. Cardiac glycosides are also toxic to humans (and probably many other animals too).