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Amsonia spp.

bluestars

Apocynaceae North America and East Asia

Attracts Pollinators Attracts Butterflies Deer Resistant Drought Tolerant Container Friendly

Native to North America

SunFull Sun – Part Shade

WaterMedium · drought-tolerant

HardinessZones 3–9

Overview

Amsonia spp. is a genus of about 20 clump-forming perennials in the dogbane family, Apocynaceae, found mostly in North America with a few species in East Asia. Upright stems carry narrow, willow-like to needle-like leaves and rise to 1-3 feet (30-90 cm). In late spring the stems are topped by domed clusters of small, pale-blue, five-pointed star flowers. The foliage of several species, especially A. hubrichtii, turns golden-yellow in autumn before dying back. Cut stems exude a milky latex. Plants form dense mounds in sun and open, loose ones in shade. The brief spring bloom, the skin-irritating latex, and a tendency for tall clumps to flop in rich soil or shade are the main constraints in the garden.

Native Range

Native mostly to the United States and Mexico, from the eastern and central states to the desert Southwest, with a few species in East Asia. Plants grow in open woods, prairies, stream banks, and rocky slopes.

Suggested Uses

Planted in mixed borders, prairie and native gardens, and massed for spring flowers and autumn foliage color. The narrow-leaved species form soft mounds that combine with ornamental grasses and later-blooming perennials.

How to Identify

Look to the upright clumps of slender stems with narrow, alternate leaves and milky sap that oozes from any cut. In late spring the stem tips carry domed clusters of pale-blue flowers, each with five narrow, pointed lobes. Slender paired seed pods follow. Autumn foliage of the narrow-leaved species turns clear golden-yellow.

Appearance

Size & Dimensions

Height1' - 3'

Width/Spread2' - 3'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~3 weeks

Spring

Pale-blue star flowers open in late spring, roughly April to June, in domed terminal clusters that last about three weeks. A light shearing after bloom can produce a tidier mound, though usually not a second flush of flowers.

Detailed Descriptions

Flower Description

pale blue to steel-blue

Foliage Description

green, turning golden-yellow in autumn

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 6-8 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range6.0 - 7.5(Neutral)

357912

Soil Types

loam clay sand

Drainagewell drained

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

2-3 years to full size

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Amsonia spp. grows in full sun to part shade in average, well-drained soil and is drought tolerant once established. Most species are hardy to USDA zone 4 or even zone 3, and they accept a wide range of soils, including clay. Plants grown in shade or rich, moist ground tend to flop and open at the center. The milky latex in the stems deters deer and rabbits. Little feeding is needed, and the clumps are long-lived without division.

Pruning

Plants are sheared back by about one-third after flowering to keep a dense mound and limit flopping. Stems are cut to the ground in late winter once the autumn color has faded. Division, if wanted, is done in early spring.