Blue Ridge St. John's-wort

Size, growth and what to expect

No source rates its growth. Its nearest relative, shrubby St. John's-wort, is rated slow, so our growth estimator treats it as slow, about a foot a year. It makes a low, spreading mat, mostly under a foot tall and at most about a foot and a half, and 9 to 18 inches across. Its oval leaves are up to an inch long, with dots that show clear when held to the light.

Golden yellow flowers about an inch across open at the branch tips in June and July, sometimes into August. They come alone or in clusters of up to five, each with about 100 stamens. Egg-shaped capsules a third to half an inch long follow.

It grows wild in the Blue Ridge Mountains of North Carolina and northern Georgia, at about 3,000 to 5,200 feet, and it once grew in South Carolina. Its home is seeps, moist rock crevices, granite outcrops and grassy balds, and it also takes to road banks and ditches. Hikers wear down some stands along trails.

How to grow Blue Ridge St. John's-wort

Blue Ridge St. John's-wort wants full sun and a moist, gritty soil that drains quickly, like the seeps and rock crevices it grows in. It rots in soggy ground. Set plants 2 feet apart and 2 feet from a wall. At its size it can go within 15 feet of overhead wires.

Saplings ship bare-root or potted. Plant them 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 mulch off the stems. Many St. John's-worts need light to sprout, so press the fine seed onto damp, gritty soil in spring without covering it.

Water weekly through the first summer. Its stems root where they touch the ground, so the mat widens with time. It needs no pruning.

Each flower carries both male and female parts, so there are no male and female plants to pair. Soil that stays wet can bring root rot, but no pest is known to trouble it.