How to Grow and Care for False Indigo

false indigo

The Spruce / Evgeniya Vlasova

False indigo is a large, upright perennial with leaves that are grey-green and beautiful long racemes of indigo-blue flowers that appear in April through June. The pea-like flowers are followed by black seed pods that can be left on the plant for winter interest. With its stately shape, false indigo makes a good architectural statement in the garden even after the flowers have faded. When started from nursery plants, false Indigo takes only about a year to reach its full height, but plants started from seed can take three to four years to flower. False indigo is generally planted in spring after the danger of frost has passed.

All parts of this plant are mildly toxic to humans and to animals. The alkaloid compounds that cause nausea and vomiting in people and animals may also be responsible for making this plant unpalatable to insects and thus a relatively trouble-free garden plant. Accidental ingestion by humans is often attributed to the fact that the young stems look much like asparagus as they emerge in the spring. However, the toxicity is mild enough that not all official lists bother to include the plant on their registers of dangerous plants.

Common Name Blue Wild Indigo, False Indigo
Botanical Name Baptisia australis
Family Fabaceae
Plant Type Perennial
Mature Size 4–5 ft. tall, 3–4 ft. wide
Sun Exposure Full, partial
Soil Type Moderately moist, well-draining
Soil pH Slightly acidic, neutral (5.0-6.8)
Bloom Time Late spring to early summer
Flower Color Blue
Hardiness Zones 3–9 (USDA)
Native Area North America (Eastern U.S.)
Toxicity Mildly toxic to humans, animals

False Indigo Care

False indigo plants are very adaptable and are reliably perennial in USDA Hardiness Zones 3 to 9, but gardeners will need to be patient for a while. You can start Baptisia plants from seed, but they are slow to establish. Even a young nursery plant will take at least a full year to get established before you really start seeing it bloom. On the plus side, these are very long-lived plants that may outlive their owners. The plant will spread, but slowly, and a mature clump takes on the look of a unique shrub in the landscape.

Maintenance is minimal. Plants can sometimes flop over from the center of the clump outward, especially if grown in shady conditions that cause the plant to get leggy. In some situations, a large hoop support can help keep the plant uprights. 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. You can prevent this by giving your false indigo a modest shearing after flowering. Stalks will need to be trimmed off near ground level as winter sets in—or immediately in the spring before new growth begins if you prefer to leave the seed heads in place through winter.

Light

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

Soil

False indigo prefers moderately well-draining soils, but it will tolerate dry soils once it is well established. It is not particular about soil pH but does best in soil that is slightly acidic to neutral.

Water

Keep a false indigo watered regularly for the first year, but after this, it will do well with about 1 inch of water every couple of weeks. Once established, Baptisia is relatively drought-tolerant. This is a native wildflower, and in most regions, it does fine with whatever rainfall nature provides.

Temperature and Humidity

False indigo will thrive in the garden in the conditions throughout its hardiness range, zones 3 to 9. It does equally well in dry and humid climates, provided it gets adequate soil moisture.

Fertilizer

Feeding is not necessary for these plants, and can even be counterproductive; excessive fertilizing can cause the plant to get leggy and flop over.

Types of False Indigo

The pure species, Baptisia australis, is a standout because of its striking blue flowers. There are also newer hybrid forms of Baptisia with yellow and purple flowers.

  • 'Purple Smoke': This is a hybrid of B. australis var. aberrans and B. alba. It has purple eyes in the center of the blue flowers.
  • ‘Carolina Moonlight’: This cross between B. sphaerocarpa and B. alba has butter-yellow flowers on 18-inch-long spikes that bloom for up to six weeks. The plants are 3 feet tall by 3 feet wide.
  • 'Twilite Prairieblues': This hybrid, one of several in the Prairieblue series developed by the Chicago Botanical Garden, is a cross between B. australis and B. sphaerocarpa. It has bicolor flowers, purple with buttery yellow. Plants are 3 feet tall and wide.
  • Twilite Prairieblues: This bicolor hybrid is another cross between B. australis and B. sphaerocarpa. It has deep violet-purple flowers with yellow highlights. Plants grow 3 to 5 feet tall and 4 to 5 feet wide.
  • Midnight Prairieblues: This is a complex hybrid of B. tinctoriaB. alba, and probably B. australis. Its flower spikes are extremely long (24 inches), deep blue-violet in color. Mature plants grow 4 to 5 feet tall by 3 1/2 to 4 feet wide.
  • Solar Flare Prairieblues: This is another complicated hybrid, probably derived from B. alba, B. tinctoria, and B. australis. The flower color changes from buttercup yellow to warm apricot, then to plum as the flowers age. The plants grow 3 to 4 feet tall and 4 feet wide.
closeup of false indigo

The Spruce / Evgeniya Vlasova

closeup of false indigo

The Spruce / Evgeniya Vlasova

false indigo pods

The Spruce / Evgeniya Vlasova

false indigo in landscaping

The Spruce / Evgeniya Vlasova

Pruning

The only pruning required for this plant is to remove the dead stems at some point, either in the late fall or early winter, or in the spring before new growth begins. Because this plant takes on such a shrub-like appearance, you can also shape it by pruning, which is best done immediately after its flowering period is over.

Propagating False Indigo

Because false indigo plants have long taproots, they are difficult to divide; however, they do grow well from stem cuttings. Here's how to do it:

  1. In April to early May, use a sharp pruner to take stem cuttings about 6 inches long, containing at least two sets of leaves and at least one set of leaf buds near the bottom of the cutting.
  2. Dip the end of the cutting in rooting hormone and plant it in a small pot filled with standard potting mix. Moisten the potting mix.
  3. Place the pot and cutting in a plastic bag or another form of plastic covering. Keep the pot in a bright, uniformly warm location, monitoring it frequently and lightly watering it if the potting mix dries out. In about eight weeks, the cutting should be rooted.
  4. When the cutting has rooted, remove the plastic and continue growing the new plant until it is large enough to plant into the garden.

How to Grow False Indigo From Seed

Growing false indigo from seed is possible, though not recommended. False indigo seeds have a hard outer coating, and 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.

But growing from seed is a lengthy process, as the plants will take three to four years before developing the size required for meaningful blooms. Thus, most people propagate these plants through stem cuttings.

Overwintering

There is almost no required winterizing routine for these plants. Many people cut off the stems to ground level as winter approaches, but even this can be omitted if you want to leave the seed pods in place for winter interest. And in borderline zones where winters are damp and above freezing, clearing the ground of plant debris is a good idea to keep the soil from being too soggy and possibly causing root rot.

Common Pests & Plant 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 Baptisia seeds, but this is a problem only if you are saving the seeds to plant.

How to Get False Indigo to Bloom

Getting false indigo to bloom is usually just a matter of patience, as it can take three or four years, or even more, before the clump is mature enough to make a meaningful display. A plant growing in shady conditions may experience reduced blooming; prune out nearby trees and shrubs that shade the plant to increase its blooming. Finally, flowering can be compromised if you prune too early, before the flower buds have developed. If you need to prune the plant for shape, make sure you wait until summer, when the flowering is done.

Common Problems With False Indigo

Few plants are more trouble-free than false indigo. But rarely, there are a couple of issues you may need to address.

Flopping Plants

When the plant is growing in shady conditions, the stems may grow leggy in their effort to reach the sun, causing the stems to eventually flop over, usually from the center outward. Sometimes, pruning of surrounding trees can increase the amount of sun and prevent this flopping. Or, a large segmented hoop support can help keep the stems upright. Relatively hard pruning after flowering is complete can also keep the plants shorter and bushier, eliminating the flopping problem.

Crown Rot

In soils that are too water-saturated for long periods, false indigo may develop root rot that causes the plant to turn mushy and collapse. Soil amendments around the plant can improve the soil's drainage. Some earthmoving to redirect water can also help eliminate puddling that causes root rot. Badly affected plants are not salvageable and will need to be removed.

FAQ
  • How did false indigo get its common name?

    False Indigo (Baptisia australis) is a native wildflower. Its common name is traced to early European settlers and traders who paid Native Americans to grow this plant for the dye they could make from the blue flowers. True indigo was extremely expensive and Baptisia australis made a passably good substitute—and it grew like a weed.


  • Are there other Baptisia species to consider?

    There are several other North American native flowers that are also cultivated for landscape use. Each has a number of natural variations, and some also have named cultivars.

    • Baptisia albescens (spiked white indigo) has white flowers and copper seed pods. It is native to the Southeast U.S. and grows to 2-4 feet in height.
    • Baptisia bracteata (false cream indigo) is a compact, 24-inch plant with long sprays of pale yellow flowers. It is native to the Eastern U.S.
    • Baptisia sphaerocarpa (yellow false indigo) is native to the lower Midwest and Gulf states. Growing 2 to 3 feet tall, its long yellow flowers spikes are 12 to 15 inches long. 'Screaming Yellow' is a popular cultivar.
    • Baptisia tinctoria (also known as yellow false indigo) is native throughout the East Coast and Midwest. It has bright yellow or creamy flowers and blooms later than other Baptisias, in later spring through early summer. Growing 2 to 3 feet tall, its flower clusters are usually only about 4 or 5 inches long.
  • How can I use false indigo in the landscape?

    False Indigo blends beautifully with pastel, late spring bloomers, like peonies, as well as with shocking colors. Spiky plants, such as 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 your false indigo plant 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.

    This plant is also a good addition to wildlife gardens, as it serves as host to several species of butterflies.