Amsonia hubrichtii

Arkansas Bluestar

Central United States (Arkansas, Oklahoma)

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At a Glance

FoliageDeciduous
Height30-36 inches (75-90 cm)
Width36-48 inches (90-120 cm)
Maturity3 years

Growing Zones

USDA Hardiness Zones

4 - 9
These zones indicate the coldest temperatures this plant can typically survive.
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Frost Tolerancehardy

Overview

Amsonia hubrichtii is a clump-forming perennial reaching 30–36 inches (75–90 cm) tall and 36–48 inches (90–120 cm) wide with a dense, billowing mound of extremely fine-textured foliage. Leaves are alternate, needle-like, 2–4 inches (5–10 cm) long and 0.04–0.08 inch (1–2 mm) wide — the narrowest foliage in the genus. The foliage mass has the visual texture of soft thread or fine hair. Terminal clusters of 5-petaled, star-shaped flowers open pale ice-blue, each 0.5 inch (1.3 cm) across, in April through May. Bloom lasts approximately 3 weeks. Fall foliage turns brilliant golden-yellow, typically persisting for 3–4 weeks in October through November. Fall color is among the most consistent and long-lasting of any native perennial and develops reliably in full sun. Stems exude milky white sap when cut. Plants expand slowly by crown growth, reaching mature width of 48 inches (120 cm) in 3 years. Clumps are exceptionally long-lived, persisting 15+ years without division. In rich soils or shade, stems flop open by midsummer, exposing the center. Self-seeding occurs modestly in open, well-drained soils. All parts contain alkaloids and are toxic if ingested. Named for Leslie Hubricht, who rediscovered the species in 1942.

Native Range

Native to a restricted range in the Ouachita Mountains of central Arkansas and eastern Oklahoma. Found in rocky, gravelly streamsides and open woodland in the Ouachita and Novaculite formations. Listed as a species of conservation concern in Arkansas.

Suggested Uses

Commonly planted in perennial borders, mass plantings, and native plant gardens at 30–36 inch (75–90 cm) spacing. Fine-textured foliage mass and fall color provide three-season interest. Drought tolerance and deer resistance suit low-maintenance landscapes. Not suited to rich, moist soils or shaded sites where the mounding habit collapses.

How to Identify

Distinguished from all other Amsonia species by extremely narrow, needle-like leaves 1–2 mm wide — the finest foliage in the genus. Compared to A. ciliata, leaves are narrower and lack the ciliate (fringed) margin hairs. Compared to A. tabernaemontana, leaves are dramatically finer-textured (needle-like vs. lance-shaped). Overall habit is wider than tall, forming a billowing mound 36–48 inches (90–120 cm) across. Milky sap exudes from cut stems.

Appearance

Size & Dimensions

Height2'6" - 3'
Width/Spread3' - 4'

Reaches mature size in approximately 3 years

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~3 weeks
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Flowers April through May in zones 4–9. Individual clusters last 2–3 weeks. In zones 8–9, bloom begins in late March. Flowers are pale ice-blue, slightly lighter in color than A. tabernaemontana.

Detailed Descriptions

Foliage Description

Bright green, extremely fine-textured, needle-like

Growing Conditions

Sun Requirements

Requires 6-10 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 Range5.5 - 7.5(Neutral)
357912
Drainagewell drained

Water & Climate

Water Needs

Low

Frost Tolerance

hardy

Time to Maturity

2-3 years

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Water regularly during the first growing season. Established plants tolerate prolonged drought and a wide range of soil types from sand to clay. Full sun produces the densest habit and most consistent fall color; stems flop in shade or rich, moist conditions. If flopping occurs, shear by one-third immediately after bloom in June. No fertilization is needed. Clumps are extremely long-lived and rarely need division. Self-seeding is modest. All parts are toxic if ingested.

Pruning

Cut all stems to 4–6 inches (10–15 cm) in late winter (March) before new growth. If stems flop, shear by one-third immediately after bloom in June; regrowth forms a dense mound by late summer. Dried stems can be left standing through winter for structural interest. No division needed for 15+ years.

Pruning Schedule

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summerearly spring

Maintenance Level

very low

Container Growing

✓ Suitable for container growing

Minimum container size: 5 gallons

⚠️ Toxicity Warning

Toxic to pets and humans