Illustration
Blue Indigo
Baptisia australis
Also called blue false indigo, blue wild indigo and wild blue indigo
Blue Indigo blooms from May through June.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Blue Indigo
Plant it in full sun. It prefers moderate water. It is hardy in USDA zones 3–9. Expect it to reach about 3.5 ft tall and 3.5 ft wide at maturity, in roughly 3 years (checked).
Is Blue Indigo toxic to cats?
- Not yet checked for dogs.
- Listed as toxic to cats by NC State Extension.
- Listed as poisonous to people by NC State Extension.
Lists differ and none is complete. If a pet eats a plant and seems unwell, call a veterinarian or a pet poison helpline.
What was checked
Nine facts were checked against named botanical sources, each recorded beside the sources that carried it: mature height and spread, hardiness zones, sun, water, bloom months and color, the trait tags, and years to mature size, which rests on a recorded house rule where no publisher states one and is marked so. Soil, diseases, pests, toxicity and the plant's own names have not yet been read for this plant, and its trait tags are the ones a feature uses rather than every word a page prints. Each fact above carries its own mark. The planting, spacing and size sections are derived from these checked facts by a fixed rule, not checked separately, and the plant type is the library's own classification.
When to plant Blue Indigo
Plant Blue Indigo in early spring as soon as the soil is workable, or in early fall at least six weeks before your first frost, so roots establish in cool weather. In zone 6, the middle of its hardy zones 3 to 9, spring means March to May and fall means August or September. Once settled, it blooms from May to June.
Month-by-month timing for your zone is on the planting calendar; if you garden near zone 6, the middle of this plant's hardy range, start with zone 6 in March. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.
How big does Blue Indigo get?
3.5 fttall5 ft 7 inan adult3.5 ftwideSee Blue Indigo in a garden plan: the planner shows it in 3D beside everything else you add, growing toward this size over the years.
How far apart to plant Blue Indigo
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Blue Indigo about 3.5 ft apart, center to center, so each plant has room to reach its full width.
Add Blue Indigo to a garden plan and the planner draws it at its full width, so you see the spacing before you buy.
Where these facts come from
Blue Indigo's height, spread, hardiness zones, sun, water, bloom color, years to mature size and trait tags were checked against 7 published sources on October 15, 2026. Each one is linked below with every fact it carried, which can include a fact this page still marks as not yet checked, because a source carrying a value is not the same as the value being held to the standard. Facts not in that list, and the planting, spacing and size sections, are not covered by these sources.
- Missouri Botanical GardenPlant Finderheight, spread, hardiness zones, sun, water, bloom months and color and trait tags
- NC State ExtensionPlant Toolboxheight, spread, hardiness zones, sun, water, bloom months and color and trait tags
- University of Wisconsin HorticultureUniversity of Wisconsin-Madison Division of Extension, Wisconsin Horti...height, spread, hardiness zones, sun, water, bloom months and color and years to mature size
- Plant Addictsheight, spread, hardiness zones, sun, water and bloom months and color
- University of Illinois ExtensionHort Answersheight, hardiness zones, sun, water, bloom months and color and trait tags
- Lady Bird Johnson Wildflower Centerheight, spread, sun, water and bloom months and color
- Prairie Moon Nurseryheight, hardiness zones, water and bloom months and color
How the checking works, and what each standard covers, is on the verified plants page.
Good to know about Blue Indigo
Curated from university extensions, botanic gardens and other primary sources, with the source named on every note.
Safety
Mildly toxic if eaten. All parts hold quinolizidine alkaloids; severity is low, with nausea, vomiting and diarrhea only if eaten in quantity. per NC State
Explore similar plants
You might also like
Design a garden with this
Drop this plant onto a 3D plan, see how it fills in, and watch your whole garden bloom across the year.