Blue false indigo Baptisia australis
Blue false indigo (Baptisia australis) is a deciduous perennial flowering plant in the Fabaceae family, native to Eastern and central United States. It grows 90 cm–1.2 m (35 in–3.9 ft) tall and 90 cm–1.2 m (35 in–3.9 ft) wide, wants full sun and low water, and is hardy to about -38 °C (-36 °F). Space plants about 90 cm (35 in) apart.
Plan Blue false indigo in your garden →
Free. Draw your beds, then watch it grow through the year in 2D and 3D.
Blue false indigo at a glance
| Type | Perennial flowering plant, deciduous |
|---|---|
| Family | Fabaceae |
| Mature height | 90 cm–1.2 m (35 in–3.9 ft) |
| Mature spread | 90 cm–1.2 m (35 in–3.9 ft) |
| Spacing | 90 cm (35 in) centre to centre |
| Sun | Full sun, at least 6 h of direct sun a day |
| Water | Low; drought tolerance high, waterlogging tolerance none |
| Soil pH | 5.5–7.5 |
| Cold hardiness | About -38 °C (-36 °F) once established (roughly USDA zone 3) |
| Heat stress | Likely above about 38 °C (100 °F) |
| Flowering | from about May for 3–4 weeks (northern hemisphere; later in cold climates, earlier in warm ones) |
| Wind tolerance | Moderate |
| Pollinator value | High |
| Edible | Not grown as food |
| Native to | Eastern and central United States |
| Common in gardens of | 🇺🇸 United States, 🇨🇦 Canada, 🇬🇧 United Kingdom, 🇩🇪 Germany |
Is Blue false indigo toxic?
- People: moderately toxic
- Cats: moderately toxic
- Dogs: moderately toxic
- Parts: all parts, seeds
Contains quinolizidine alkaloids (cytisine).
If a child or pet may have eaten part of a plant, call a poison centre or vet straight away.
Companion planting: what to grow with Blue false indigo
Good neighbours
- good With Sweet corn: "Three sisters": climbing beans use corn as a support and fix nitrogen; the benefit to the corn is modest but real in low-input soils. Evidence C
Keep apart or take care
- caution With Alliums (onion family): Onions, garlic and leeks are said to stunt beans and peas (allium root exudates may reduce nodulation). Traditional companion-planting advice; controlled trials are few, so treat it as a soft preference. Evidence D
- caution With Alliums (onion family): Beans and peas are traditionally kept away from onions, garlic and leeks. Traditional companion-planting advice; controlled trials are few, so treat it as a soft preference. Evidence D
- caution With Fennel: Fennel is reported to suppress beans and peas growing next to it. Evidence C
Questions about Blue false indigo
- How far apart should I plant Blue false indigo?
- About 90 cm (35 in) apart, centre to centre. A mature plant spreads 90 cm–1.2 m (35 in–3.9 ft).
- Does Blue false indigo need full sun?
- Full sun: at least 6 hours of direct sun a day.
- How much water does Blue false indigo need?
- Low water. Drought tolerance is high and waterlogging tolerance none.
- How cold-hardy is Blue false indigo?
- It tolerates about -38 °C (-36 °F) once established, roughly USDA zone 3.
- When does Blue false indigo flower?
- From about May for 3–4 weeks (northern hemisphere; later in cold climates, earlier in warm ones).
- Is Blue false indigo poisonous to cats and dogs?
- For cats it is moderately toxic; for dogs moderately toxic; for people moderately toxic. Contains quinolizidine alkaloids (cytisine).
- What grows well with Blue false indigo?
- "Three sisters": climbing beans use corn as a support and fix nitrogen; the benefit to the corn is modest but real in low-input soils.
Sources and evidence
Evidence grade A (A: strong evidence).
- Missouri Botanical Garden Plant Finder, Missouri Botanical Garden
- Native Plant Information Network, Lady Bird Johnson Wildflower Center, University of Texas at Austin
Notes and assumptions
- Lupin-like indigo spikes in late spring, then rattling black pods. Deep taproot: plant once and leave; very long-lived.
Reference values for planning, not horticultural, veterinary or medical advice. Varieties, soils and local climates differ: check with a local nursery or extension service.
Related plants
- Bush bean Phaseolus vulgaris
- Garden pea Pisum sativum
- Sweet pea Lathyrus odoratus
- Runner bean Phaseolus coccineus
- Broad bean (fava) Vicia faba
- Lima bean Phaseolus lunatus
- Cowpea (black-eyed pea) Vigna unguiculata
- Yardlong bean Vigna unguiculata subsp. sesquipedalis