Geranium psilostemon - glorious eye-searing magenta!
Having preached the virtues of foliage, I wouldn't want to leave the impression that I don't enjoy a good hit of colour, especially at this time of year.
You can't really get a flower of more intense colour than Geranium psilostemon, the Armenian cranesbill. With its combination of magenta and black, it is certainly a plant that requires suitable consideration when placing it in a planting scheme. However, suitably sited, it is a wonderfully bold and joyous character in the garden, combining both a flamboyant display and considerable vigour!