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Plant of the Week
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| Japanese bush clover is a mounded subshrub that flowers in late summer. (Photo courtesy Gerald Klingaman) |
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| Heatwave is one of the narrow leaved species native to the southwestern states and better suited to a warmer location in the landscape. (Photo courtesy Gerald Klingaman) |
My plant training officially began in high school when my ag teacher, Mr. Raupe, began teaching us about the plants that grew in the pastures and fields of central Oklahoma. In the early 1960s, one of the plants, Sericea Lespedeza, was considered a good guy because it was a nitrogen-fixing legume that grew in droughty soils and prevented erosion.
However, times change, and by the 1980s, that same plant had morphed into an invasive weed threatening wildlife habitat and native vegetation. So, not surprisingly, my perception of Lespedezas is somewhat jaded – that is until I was introduced to the Japanese bush clover, Lespedeza thunbergii.
There are about 60 species of lespedezas recognized in the world, with about equal distribution between Eastern Asia and Eastern North America. About half a dozen of these – mostly Asian in origin – are semi-woody subshrubs forming stout, multi-branched clumps that freeze back towards the base each winter in accordance with how cold it gets. L. thunbergii grows 4 to 6 feet tall and wide in an arching clump, even when frozen or cut back to the base during winter.
It produces blue-green trifoliate deciduous leaves up the stem that are to 2 inches long and half inch wide. In late August and September, it produces a profusion of rosy purple pea flowers in 6-inch long panicles in the terminal nodes of the stems that pretty much cover the plant. Individual flowers have the typical legume shape and are to .75 of an inch long. Occasionally, plants will produce a few blooms in July. The fruit is a segmented pod but, because it flowers so late in the season, I have never encountered seeds.
The genus name was given by the French botanist Andrew Michaux to honor fellow botanist Vincent Manuel de Cespedes, who was serving as the Spanish governor of Florida during the late 18th century and first discovered the plant. Michaux, or possibly the publisher, garbled Cespedes’ name and it became Lespedeza when his Flora Borealis Americana appeared in 1803, a year after the Michaux’s death.
The species epitaph commemorates Carl Peter Thunberg (1743-1828), who was a Swedish naturalist who spent almost two years in Japan as a physician for the Dutch trading company that had a concession to trade with the Japanese. While there he collected plants, many of which were removed from hay brought daily to the compound on Dejima Island, where the traders were forced to remain. He was permitted to make only one expedition to the mainland, when the company was required to go to Tokyo to pay homage to the Emperor. His publication of Flora Japonica in 1784 cemented his reputation as the first western botanist to visit that country. The species L. thunbergii was not officially recognized until 1927. It is found in Japan, Korea and eastern China. The plant we know as Japanese Bush Clover may have been introduced earlier into this country, but under a different name.
The most common selection of Japanese bush clover offered in the nursery trade is ‘Gibraltar’, a free-flowering selection made by Bill Frederick, who selected it at a du Pont family estate called Gibraltar in Wilmington, Del., about 1990. A white-flowered form and a white variegated selection are also offered.
Japanese bush clover is a perfect plant for cascading over a wall or using as a background in the border. It is too big to add to the perennial border, but is a strong enough grower to mix in with woody plants in the shrub border. It should have full sun and, once established, survives considerable drought. It needs good drainage, but has no particular aversion to clay soils. Each winter, prune the plant back to the ground before new growth starts. Plants are hardy from zones 5 through 9. Propagation is by crown division or by springtime cuttings.
By: Gerald Klingaman, retired
Retired Extension Horticulturist - Ornamentals
Extension News - November 4, 2011
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