The drama of blue false indigo

June 23, 2010

From University of Illinois Extension Garden packet

URBANA, Ill.—Picture a plant that has grey-green foliage; indigo blue, pea-like flowers; and large, inflated seed pods that turn coal black and rattle in the late fall and early winter wind. That’s the dramatic 2010 perennial plant of the year, Baptisia australis, also known as wild indigo, rattleweed and rattlebush.

“The genus name Baptisia is derived from a Greek word meaning ‘to dip (dye)’ and refers to the fact that extracts from this plant were once used as a substitute for indigo dyes,” said Greg Stack, a University of Illinois Extension horticulture educator.

“Blue false indigo grows 3 to 4 feet tall and about as wide,” Stack added. “It grows across a wide range of planting sites, and is one of the most adaptable native species.”

If planted in the garden, Baptisia starts off rather slowly, producing a few sparse stems. After the second and third seasons, the plant fills out to a handsome, grey-green, shrubby plant 3 to 4 feet in width.

“Take its size into consideration when planting to allow it to develop to its full potential,” Stack said. “It is also a very long-lived perennial in the garden.”

Baptisia grows best in full sun but can survive partial shade. Under these conditions, it will tend to grow taller and may need to be staked. Plants grow best in deep, rich soils, but will tolerate poor soils and, once established, are very drought tolerant. Baptisia doesn’t need dividing from the plant’s point of view because it grows from underground rhizomes. But it might be beneficial to divide every three to four years to keep it from becoming overcrowded and consuming lots of garden space.

“This plant produces a mound of grey-green foliage early in the spring,” said Stack. The 10- to 12-inch-long flower stalks appear in late spring and carry 1-inch-long indigo blue pea-like flowers that last for about four weeks.

“After flowering, 2- to 2-1/2-inch-long, inflated seed pods appear that turn coal black,” Stack said. “As the pods dry, the seeds inside will produce a rattling sound as the wind blows. Early settlers used the seed pods as rattles for children, and now they are often dried and used in flower arrangements. Settlers also used the plant as a substitute for indigo dye.”

Baptisia is an excellent addition to the perennial garden and makes quite a statement as a specimen plant given its size, the blue-green color of its foliage, and seed pod display in the fall.

“Another plus for the plant is that there are no serious insect or disease problems,” Stack said. “And it is seldom damaged by deer browsing.”

Although the native perennial has been around for a long time, plant breeders are hard at work providing variations to the plant to add to the perennial garden palette. Baptisia “Purple Smoke” is very upright, growing to 4 feet tall. The grey-green foliage is a nice backdrop for the 1 1/2-foot-long smoky violet flower spikes. Baptisia “Solar Flare” offers lemon yellow flowers that take on an orange blush as they age. Baptisia “Starlite Prairieblues” offers vivid violet buds opening to periwinkle flowers and light yellow keel. And, finally, Baptisa “Twilite Prairieblues” has purple buds opening to violet flowers and a lemon yellow keel. It also forms large, mature clumps quickly.

“The 2010 award winner has the ability to add color and interest to your garden for well over 100 years,” Stack said.

From the June 23-29, 2010 issue

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