Anchusa Blue Angel

Real blue is the rarest colour in a garden. Most of what gets sold as blue is violet, lavender or purple-blue. 'Blue Angel' is an actual saturated ultramarine, carried in airy sprays of forget-me-not flowers above a tidy 30 to 45cm mound.

It comes from the South African Cape and it behaves like it. Lean, dry, free-draining ground in full sun gives the best plants and the strongest colour; rich moist soil gives soft growth and washed-out flowers. It is one of the few annuals that genuinely prefers the hot dry awkward corner nobody knows what to do with.

The one thing it will not forgive is being left to set seed. After the first flush it decides its job is done and stops, sometimes by the end of July. Keep the old flowers picked off and it will run from June to the first frosts instead. The foliage is bristly and not much to look at, so it sits better in the middle of a planting than on show at the front. Bees, hoverflies and butterflies work it constantly.