Explore the Indigos

What do you call a plant that loves poor clay soil, is deer and insect resistant, hardy, drought tolerant, long-lived, well behaved and has four-season interest? The false indigo, baptisia— perennial plant of the year. This native plant was mentioned in the spring issue of the Trumpet Vine, but really deserves more attention.

One look at the flower tells you this is a member of the legume family and it fixes its own nitrogen. It actually thrives in poor soil so don’t waste your good compost on this plant! Baptisia australis, pictured here, has a deep blue flower and stays in bloom for a month or more. Other colors include white, yellow, purple and burgundy. The plant pictured at the bottom is Baptisia sphaerocarpa or ‘Screaming Yellow.’ Pollinators—bees and butterflies—are attracted to baptisia. Baptisias hybridize readily if they are grown in the same vicinity with each other. So you may create your own cultivars over time

Indigos come up quickly in the spring and tall spikes of flowers bloom above the foliage in May or June. Then they continue to grow new gray/green leaves keeping the plant looking fresh throughout the summer. Later in the summer the leaves darken with a silvery dusting. In the winter, attractive black seed pods remain on the stalks and can be used in arrangements. Indian children used the dried pods with loose seeds as rattles. Mature indigos are usually about three feet high and equally wide. A mature clump looks like a shrub. Indigos do best in full sun, they are not shade tolerant.

Indigos develop long tap roots. This allows them to be drought tolerant once they are established. It may also explain why they are slow to mature and don’t bloom until their second year. This is one case where it’s better to purchase a larger, more mature plant. The tap root also makes it difficult to transplant an established plant.

If a fresh leaf is crushed or stem broken the sap turns a slate blue color when exposed to the air. The Cherokee and early settlers used it as a source of blue dye. A common name, false indigo, indicates that the plant is not the true indigo, Indigofera tinctoria, that was imported from India for use as blue dye.

Indigos are also appropriate for the herb garden. Some Indian tribes used it for medicinal purposes. The Osage made eyewash from the plant. The Cherokees would make a tea from it. A hot tea was taken as a purgative and a cold tea to prevent vomiting. A pulverized root or hot tea was held over a sore tooth to relieve the pain. Recent German research indicates some baptisia species may act as stimulants to the human immune system.

Propagate indigos from seed, which should be soaked in hot water for a day or two until they swell; then they will germinate in about 20 days. Seeds planted in fall or early winter do not need pretreatment to germinate. It also is possible to divide the root by carefully cutting it with a sharp knife and then watering the transplants frequently. Once established, indigos will remain healthy for several years; they won’t get weedy or aggressive. They are a tough but well-behaved native that will give your garden four-season interest.

Carol Ivory, Loudoun County Master Gardener