Creeping Mazus

Mazus miquelii is a creeping evergreen to semi-evergreen ground cover from temperate East Asia and the Himalaya, three to six inches high and spreading steadily by rooting stems. Small tubular two-lipped flowers in blue, violet or white, each marked with a yellow throat, cover the mat through late spring and summer above neat toothed leaves.

It takes light foot traffic and wet ground, an unusual pair, so it works in paving joints, along stepping stones and in the damp margins of a rain garden. It spreads quickly and is naturalised from New England to Virginia, so keep it away from unmanaged ground and confine it with an edge where it meets a lawn.