Achillea Ballerina

Small double white buttons, ruffled and about the size of a shirt button, carried in clouds above neat dark green foliage from June into early autumn. It gives you the froth that gypsophila gives, from a hardy perennial that comes back every year.

The useful thing about 'Ballerina' is that it is bred from our native sneezewort rather than the common yarrow, so it is a plant of damp meadows at heart. It will grow in the heavier, moisture-retentive ground that makes most yarrows sulk. At 40 to 60cm it stands up on its own and keeps standing after a July downpour, which is more than can be said for a lot of white fillers.

Two honest warnings. It spreads by underground rhizome and will keep going if you let it, so lift and divide every third spring or give it room where a bit of travel does not matter. And a single plant looks like nothing at all. Five or seven together give you the cloud; one gives you a few white specks. It cuts well and dries better.