Salvia uliginosa

Salvia uliginosa, the bog sage, is an airy, sky-blue perennial grown for clouds of clear, cool blue flowers held on tall, slender, branching stems from midsummer into fall. The species name uliginosa means of marshes, and the plant lives up to it, thriving in the moist ground most sages refuse, so the bog sage fills a niche few others in the genus can.

Native to the wetlands of Brazil, Uruguay, and Argentina, the plant builds a tall, upright, open clump of four to six feet, clothed in narrow, aromatic, bright green leaves. The small flowers are a pure, luminous sky-blue, often with a small white eye, and their airiness lets the bog sage weave through stouter neighbors like a blue haze rather than a solid block of color.

Vigor is the thing to watch. In moist, happy ground the bog sage spreads freely by running roots into a broad colony, so give room, a contained bed, or a naturalistic setting where the wandering is welcome. The long run of blue draws bees, butterflies, and hummingbirds through the second half of the season.

Site Salvia uliginosa in full sun to light shade in moist to average soil, at the back of a border, in a rain garden, near a pond or water feature, or in a damp meadow planting, and pair the sky-blue with warm-season grasses, Joe-Pye weed, and the golds of late summer. Stake or let the tall stems lean through companions, and cut the old growth down in late winter. In colder gardens the plant returns from the root, and where it runs too far, simply pull the strays.