Cumberland Rosemary

Size, growth and what to expect

No source rates its growth, and the site carries no close relative, so our growth estimator uses its medium rate, about a foot and a half a year. It makes a low, spreading shrub 1 to 2 feet tall and as wide, often a mat of sprawling stems that root as they go. Its needlelike leaves, about three quarters of an inch long, are dark green above and pale beneath.

Two-lipped, lavender-pink flowers up to an inch long, spotted purple in the throat, open in May and June. Tiny nutlets ripen in June and July, and few of them hold a fully formed seed.

It grows wild only along the Big South Fork of the Cumberland, the Obed and the Caney Fork rivers on the Cumberland Plateau, in about 35 stands in Tennessee and southern Kentucky. Its home is sunny boulder, cobble and gravel bars, sand bars and islands, where spring floods keep taller plants away. Most stands hold fewer than 100 clumps.

How to grow Cumberland Rosemary

Cumberland rosemary wants full sun and takes a little shade. It needs sharp drainage in a lean, slightly acid sand or gravel, and once established it takes drought. Taller plants that close in over it are its main foe, so keep it clear of them. Plant it 2 feet from a wall and set plants 2 feet apart. At its size it can go within 15 feet of overhead wires.

Saplings ship bare-root or potted. Plant in early spring or early fall, in a hole wider than the roots and no deeper. Set the crown at the soil line, put the native soil back in, and keep any mulch clear of the stems. Its seed sprouts poorly, about 2 in 100 in laboratory tests, because few seeds hold a full embryo. Sow it on the surface of damp sand in good light, since buried or dark seed does not sprout. Most seedlings that appear do so within three weeks, and fungi kill many.

Water weekly through the first summer if rain is short, then let it ride out dry spells. Its low branches root where they touch the ground and spread into a mat. Old clumps can be short-lived.

Each flower carries both male and female parts, and bumblebees, honey bees and other large bees carry the pollen. Its own pollen sets far fewer good seeds than pollen from another plant. No serious insect or disease troubles it. Saplings are shipped only in state and otherwise pickup only.