Feverfew

Clouds of small white daisies with yellow button centres on branched stems above finely cut ferny foliage, from June through to September. Nothing about it is showy, and it is one of the most useful things in the garden.

Its main job in a border is feeding hoverflies, whose larvae eat aphids in serious numbers. That is why cottage gardeners have traditionally run feverfew along the edges of the vegetable beds rather than in the flower border. In the vase it is the filler that lifts a heavy arrangement, and at ten to fourteen days it outlasts most of what it is put with. It dries to a warm cream and keeps its daisy shape for wreaths.

Two honest points. The foliage has a sharp camphor smell when brushed that some people dislike quite strongly, so crush a leaf before you commit a path edge to it. And it self-seeds enthusiastically. It is a short-lived perennial giving two or three years per plant, and it keeps a colony going by seeding freely, which means that once you have it, you have it. Seedlings pull easily while they are young.