Russian sage (Perovskia) is one remarkable flowering perennial. You can grow it just about anywhere in the United States, so it's available in garden centers or from mail-order nurseries nationwide.
Perovskia was named by the Russian botanist Karelin about 1840 to honor a Turkestani statesman, B.A. Perovski. He was governor of Orenburg, a Russian city 1,500 miles northwest of the plant's native region. These are its only links to Russia. The species is native to the steppes of Afghanistan, so might more accurately be known as Afghan sage. The plant is called sage for its relation to the culinary sages. A member of the mint family, it shares the squared stems and aromatic qualities of its cousins.
Woody stems are silver and leaves are grayish, 1 inch long and slightly toothed. Height is nearly 4 feet. Flowers are small, light blue to lavender, and arranged in whorls along the stem. Flowering spikes are 12 inches long or more.
Depending upon your climate, flowering begins in late spring or midsummer. Perovskia often continues to bloom through September and until a hard frost.
Russian sage is one of the most heat and drought-resistant perennials available. Cold hardy to nearly -40 °F, it grows in USDA hardiness zones 3 through 10.
Mike Heger of Ambergate Gardens, Waconia, Minnesota (zone 4), treats Russian sage like an herbaceous perennial that dies back in winter. I live in central Pennsylvania (zone 5) and my plants die back to the ground, too. In zones 9 and 10, Russian sage grows well but is more like an annual or biennial. Plants usually die within two years, but might reappear from seedlings or root suckers, according to Randy Baldwin, San Marcos Growers, Santa Barbara, California (zone 10). He adds that supplemental summer water seems to enhance longevity.
Perovskia loves heat, so generally performs best in areas with warm summers, even if humidity is high. Some shade is okay, but too much makes plants sprawl. Soil should be neutral to alkaline. Poor drainage, especially in winter, is deadly.
There are seven species of Russian sage, but only a few are available. Perovskia atriplicifolia is most common. The one currently sold in the U.S., however, is likely a hybrid between P. atriplicifolia and P. abrotanoides and is nearly identical with the variety 'Blue Spire'. The first to flower in spring is 'Blue Mist', which, along with 'Blue Haze', has lighter blue flowers than the species. 'Blue Spire' has deep purple flowers and larger panicles. Lavender-blue 'Longin' has stiff upright stems and a more formal appearance than the species. 'Filigrin' is a compact variety with deeply cut foliage and bright blue flowers.
Modest amounts of supplemental water are necessary in hot and dry climates. Cut old stems back to the ground once a year in spring before new growth begins. In coldest climates, leave stems standing in winter to trap snow for a deeper mulch.
Perovskia's open growth and light blue flowers combine nicely with many other plants. Use it for a large-scale ground cover, as a filler in borders and to separate more dominant colors. One striking companion is white-flowered phlox. Perovskia also combines well with coreopsis, English lavender, and gloriosa daisy.
Dr. David J. Beattie is a professor of ornamental horticulture at Pennsylvania State University.