Amsonia, Genus, illustris, Species,
- Genus & species
shining bluestar
Central United States (Missouri, Arkansas, Oklahoma, Kansas, Texas)
Overview
Amsonia illustris is a clump-forming perennial reaching 30–42 inches (75–105 cm) tall and 30–36 inches (75–90 cm) wide with a dense, upright habit. The species epithet 'illustris' (shining) refers to the glossy, leathery texture of the foliage that separates this species visually from other Amsonia. Leaves are alternate, lance-shaped, 3–5 inches (8–13 cm) long and 0.5–1 inch (1.3–2.5 cm) wide, dark green with a glossy upper surface. Foliage is broader and more leathery than A. hubrichtii or A. ciliata. Terminal clusters of 5-petaled, star-shaped flowers open medium blue to steel-blue, each 0.5–0.75 inch (1.3–2 cm) across, from April through June. Individual clusters last 2–3 weeks. Stems exude milky white sap when cut. Fall foliage turns golden-yellow, persisting 2–3 weeks in October. Plants expand slowly by crown growth. Clumps persist 10+ years without division. Compared to A. tabernaemontana, A. illustris tolerates wetter soils and naturally grows along stream margins and gravel bars. Stems may flop in partial shade or in soils with above-average nitrogen. All parts contain alkaloids and are toxic if ingested.
Native Range
Native to the central United States, from Missouri and Kansas south through Arkansas and Oklahoma to Texas. Found along stream banks, gravel bars, floodplain edges, and moist prairies at 300–1,500 feet (90–450 m) elevation. Grows in moister habitats than A. hubrichtii or A. ciliata.Suggested Uses
Planted in perennial borders, rain gardens, and moist meadow plantings at 24–30 inch (60–75 cm) spacing. Moisture tolerance suits sites too wet for A. hubrichtii or A. ciliata. Glossy foliage adds textural contrast in mixed borders with matte-leaved perennials. Not suited to deep shade or sites where stem flopping cannot be managed.How to Identify
Appearance
Size & Dimensions
Height2'6" - 3'6"
Width/Spread2'6" - 3'
Bloom Information
Flowers April through June in zones 4–9. Individual clusters last 2–3 weeks; total bloom extends about 3 weeks. In zones 8–9, bloom begins in late March. Flower color is medium blue to steel-blue, 1–2 shades deeper than A. hubrichtii.
Detailed Descriptions
Flower Description
medium blue to steel-blueFoliage Description
glossy dark green, lance-shaped, leathery; golden-yellow in fallGrowing 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
Care & Maintenance
Care Guide
Plant in moist to average soil with a pH of 5.5–7.5 in full sun to partial shade. Water weekly during the first growing season. Established plants tolerate short drought intervals of 2 weeks and grow in soils from consistently moist to moderately dry. Tolerates wetter conditions than A. hubrichtii or A. ciliata and performs in rain gardens and moist meadow plantings. Stems flop in partial shade or over-rich soils. Shearing by one-third in June after bloom restores density in flopping plants. Clumps persist 10+ years without division. All parts contain alkaloids and are toxic if ingested.Pruning
Cut all stems to 4–6 inches (10–15 cm) in late winter (March) before new growth emerges. Shearing by one-third after bloom in June restores density if stems become lax; regrowth forms a full mound by late summer. Dried stems can remain standing through winter for structural interest.Pruning Schedule
Prune: March & June
early springsummer
Container Growing
Suitable for container growing
Minimum container size: 5 gallons
