Around 9 species of annual or perennials, from the Mediterranean. Leaves are normally opposite and have a fleshy feel. Masses of flowers are produced, in branched heads, red, white or pink. Suitable for an open garden spot and tolerant of drought and coastal conditions. Centranthus is derived from the Greek kentron, meaning 'spur' and anthos, meaning 'flower'. Each small flower indeed does have a long spur, hence the common name red spur valerian.
The flowers with a long spur which holds nectar make these plants very attractive to long-tongued insect visitors, e.g. butterflies and hummingbird hawkmoths, together with a range of longer-tongued bees. They are particularly valuable in droughty locations where the flowers of other species may fade. Although not native, and now being found in natural rock and shingle habitats as well as on walls and brownfield sites, C. ruber is so well-established in the wild that steps taken to try to contain its spread from gardens (even if this were possible given that each seed comes with a little parachute) would be ineffective.