How big does Blue false indigo grow?

About 1.2 m × 1.2 m after ten years (height × width). Its ultimate size is 0.9–1.2 m × 0.6–1.2 m.

What soil does Blue false indigo grow in?

It tolerates these soils: average garden soil, clay.

Is Blue false indigo hardy?

Hardy down to -40 °C (USDA zone 3, RHS H7). It gets through winter in every part of the country.

Is Blue false indigo toxic to children?

Yes, it is mildly toxic to children.

When does Blue false indigo flower?

Flowering: May–June, blue, purple.

How much water does Blue false indigo need?

Water need: low. Drought tolerance: high.

Blue false indigo

Baptisia australis

Blue false indigo (Baptisia australis) is a perennial that reaches 1.2 m × 1.2 m after ten years. Light: full sun, part shade. Hardy down to -40 °C. Drought tolerance: high. Mildly toxic to children. Sold in local shops from about €6.

Illustration of Blue false indigo — An illustration of the typical shape of the mature plant, not a photo.

What it's good for, and what it isn't

A shrub-like, very long-lived perennial that carries lupin-like spikes of indigo blue flowers in late spring above blue-green, clover-like foliage, followed by inflated seed pods that ripen black and rattle. It is slow to get going and needs a few years to show what it can do, but once rooted in it copes well with drought and poorer soil. Because of its deep taproot, think carefully about where you plant it, as it dislikes being disturbed or moved later.

Watch out for

It develops slowly in the first years, and plants raised from seed take 3 to 4 years to flower. In part shade it grows leggy and can flop open after flowering, when it needs support or a trim after bloom (which means giving up the decorative seed pods). It flowers poorly in acidic soil. Because of its deep, extensive roots an old plant is difficult and risky to move or divide. Weevils often live in the seed pods. It has no serious diseases.

Key facts

Light: Full sun, Part shade
Water need: Low
Care: Low
Size after 10 years: 1.2 m × 1.2 m
Hardiness: down to -40 °C
Foliage: Deciduous
Flowering: J F M A M J J A S O N D May–June, blue, purple

Group	Perennial
Light	Full sun, Part shade
Size after 10 years	1.2 m × 1.2 m
Ultimate size	0.9–1.2 m × 0.6–1.2 m
Hardiness	down to -40 °C (USDA 3, RHS H7)
Soil	Average garden soil, Clay
Foliage	Deciduous
Flowering	May–June, blue, purple
Water need	Low
Drought tolerance	High
Maintenance	Low
Root aggressiveness	Low
Suckering	no data
Spreading	Low
Distance from buildings	no data
Distance from paving	no data
Litter	not typical
Planting distance	90 cm
For dogs	Mildly toxic (uncertain)
For cats	Mildly toxic (uncertain)
For children	Mildly toxic
Typical price	from about €6

Toxicity data is for information only. If your pet or child has eaten a plant, contact a vet or a doctor.

Sizes and prices available

The same plant is sold as a small pot and as a specimen several metres tall, and the price follows. Prices are rounded and for guidance only.

Size	Typical price
size not stated	approx. €6

Frequently asked questions

Data updated: October 8, 2026 · How our data is made

Appears in these lists

Perennials for part shade Perennials for full sun Drought-tolerant plants Drought-tolerant perennials Perennials for clay soil Perennials for pollinators Low-maintenance perennials

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