Erigeron karvinskianus Profusion

Thousands of tiny daisies, barely a centimetre and a half across, on a low tumbling mound of fine stems. They open white, age through soft pink to wine-purple, and because every flower is at a different stage the plant carries the whole progression at once and reads as a watercolour wash.

Its trick is making a garden look old. Scatter the seed into the cracks between paving, press it into the mortar joints of a wall, sow it into a gravel path, and within a couple of seasons you have curtains of daisies coming out of the stonework as though they had been there for decades. Nothing else does that job as well. It flowers from May until November, and in a mild year into December, which is one of the longest seasons of bee food in the garden.

The self-seeding that gives you the effect will also put it where you did not ask for it. Young seedlings are shallow-rooted and pull out with a finger, so it stays manageable if you keep on top of it and becomes a problem only if you leave it for a couple of years. It wants sun and sharp drainage, and a hard winter can cut it back in cold inland gardens.