How to Grow and Care for False Indigo Plant (Baptisia australis)

Baptisia australis
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No flower fills your garden with brilliant true blue flowers like blue False Indigo. False Indigo (Baptisia australis), a native American beauty traces its name to the fact that Europeans used to pay Americans to grow this plant, for the dye they made from the blue flowers. True indigo was expensive and Baptisia, which made a similarly colored dye, grew like a weed.

While False Indigo only takes about a year to reach its full height, plants started from seed do take three to four years to flower, however. After the spring late frost is the optimal time to transfer seedlings outside.

False Indigo has an upright, shrubby form with trifoliate blue-green leaves and pea-like blossoms. It offers a long season of interest, with colorful flower spikes, unusual seed pods, and foliage that is almost never bothered by pests or disease.

Botanical Name Baptisia australis
Common Names Blue Wild Indigo, False Indigo
Plant Type Perennial
Mature Size 45 feet tall, 34 feet wide
Sun Exposure Full sun
Soil Type Drier, well-draining soil
Soil pH Neutral to slightly acidic
Bloom Time Late spring to early summer
Flower Color Blue
Hardiness Zones 310
Native Area Prairies of southern North America

How to Grow False Indigo

Baptisia plants are very adaptable and are reliably perennial in USDA Hardiness Zones 3 to 10. You can start Baptisia plants from seed, but they are slow to establish and it will probably be three years before you see flowers. Even a young false indigo plant will take at least two years to get established before you really start seeing it bloom. On the plus side, they are very long-lived. If you do not deadhead the flowers, you will get attractive seed pods similar to pea pods, which turn dark and rattle in the breeze. Baptisia grows like a small shrub, reaching four to five feet tall and three to four feet wide.

You can leave the spent flowers and enjoy the seed heads. The pods are attractive and jingle in the wind. However, they can make the plants top-heavy and prone to splitting open in the center, especially plants grown in partial shade. You can prevent this by giving your False Indigo a modest shearing after flowering.

Light

False Indigo will get floppy without at least six hours of full sunlight. Full sun also prevents fungus diseases.

Soil

False indigo prefers drier, well-draining soils. It is not particular about soil pH but does best in a soil that is neutral to slightly acidic.

Water

False Indigo requires very little maintenance. Keep it watered regularly for the first year. Once established, Baptisia is very drought-tolerant.

Temperature and Humidity

Your Baptisia plant will bloom from late spring through early summer. Although in most areas it dies back to the ground in winter, False Indigo leaves turn an unattractive black with the first hard frost and the plants tend to collapse by mid-winter, so cutting them back in fall is usually recommended. False Indigo is a member of the pea family and you will notice the resemblance in its foliage and flowers, as well as its fondness for cooler weather and its tolerance to humidity.

Varieties of False Indigo

Baptisia australis is a standout because of its striking blue flowers. There are also newer hybrids of Baptisia with yellow and purple flowers.

  • 'Purple Smoke' (Baptisia x 'Purple Smoke'): a hybrid with a purple eye in the center of the blue flowers
  • 'Twilite Prairieblues' (Baptisia × varicolor 'Twilite Prairieblues'): a trademarked cross between B. australis and the yellow Baptisia sphaerocarpa, making purple flowers tinged with buttery yellow
  • 'White Wild Indigo' (Baptisia alba): a similar plant, with white flowers set against dark stems

Landscaping Uses

False Indigo blends beautifully with pastel, late spring bloomers, like peonies, as well as with shocking colors. Spiky plants, like iris, salvia, and tall alliums, complement both the color and the texture of Baptisia. The blue blossoms really bring out the chartreuse of Lady’s Mantle.

Since it is a large plant and it only blooms once, be sure to put it somewhere in your garden where its foliage will continue to offer interest. Snuggling it between other plants will prevent the branches from falling open under the weight of the flowers and seed pods.

Propagating False Indigo

False Indigo seeds have a hard outer coating. If you do decide to try growing them from seed, some type of scarification will improve germination. Soaking them in hot water for at least eight hours prior to scarifying them would be even better, although, some gardeners have luck simply planting the seeds in the fall and allowing the winter weather to soften the seed coat.

Because False Indigo plants have long taproots, they are difficult to divide; however, they do grow well from cuttings.

Common Pests/Diseases

Fungus diseases such as leaf spot, powdery mildew, and rust can occur if grown in crowded, damp conditions. Be sure to provide good air circulation around your Baptisia plants.

Weevils have been known to eat and infest Baptisia seeds. This can be a big problem if you are saving the seeds to plant. Always check your seeds before bringing them indoors.