Indigofera incarnata 'Alba'

No genus carries more Carolina history in its name than this one. Indigofera means indigo-bearing, and indigo was the blue that built the colonial Lowcountry: in the 1740s a young Eliza Lucas Pinckney coaxed a successful crop out of the land around Charleston, and for a generation the dye stood second only to rice among the colony's exports, made with skill drawn largely from enslaved West Africans, until the Revolution cut the British bounty and the fields went quiet. The plant that did that work was Indigofera tinctoria.

This is their ornamental cousin, grown for the eye rather than the vat. Indigofera incarnata is the Chinese indigo, and incarnata means flesh-colored, after the soft pink the species usually wears; 'Alba' is the white-flowered form, cooler and quieter. Fine, almost ferny pinnate leaves set off long racemes of small white pea flowers from early summer well into fall, opening a few at a time so there is always something coming.

These make a low, slowly spreading subshrub, a foot or two high and wider than that, the kind of soft-scaled groundcover that knits an awkward slope together. The flowers come on new growth, so a hard cut in late winter only improves the plant, the way it does a buddleia. Being a legume, the shrub fixes its own nitrogen and asks little of the soil.

Give 'Alba' sun, a little afternoon shade where summers run brutal, and decent drainage, and the plant will quietly cover ground that nothing tidier would forgive. Use on a bank, at the front of a border, or spilling over a low wall, where the white bloom cools a hot planting and lengthens the season; pair with grasses and late perennials, and let the bees find the flowers all summer.