Amsonia hubrichtii aka Hubricht's Bluestar

Amsonia hubrichtii is a perennial in the dogbane family. Common names include Arkansas bluestar and threadleaf blue star. Its native range runs from southeastern Oklahoma into western and central Arkansas. It grows in the Ouachita Mountains within that range. Leslie Hubricht found it there in the early 1940s. It loses its leaves at the end of the season.

Plants form upright clumps with a soft, rounded outline. Garden plants reach 2–3 feet [0.61–0.91 metres] tall and wide. RHS gives heights up to 3.3 feet [1 metre]. Its spread estimate is lower, at 0.3–1.6 feet [0.1–0.5 metres]. Growth is slow, and clumps need time to fill out. RHS gives two to five years to reach full size. Smooth green stems branch and hold thin, soft leaves. These leaves grow in an alternate pattern along the stems. Each leaf is narrow, with a smooth edge. Bright green foliage turns gold or yellow in autumn.

Small blue flowers form clusters at the stem tips. Each star-shaped flower measures about half an inch across. Dark blue buds open to pale blue blooms. Flowering dates vary among the sources and growing regions. Missouri Botanical Garden lists April to May. Chicago Botanic Garden lists May to June. RHS places bloom in early to mid-summer. Butterflies visit the flowers, which also suit cut arrangements. Slender brown follicles follow the blooms and appear in summer. These seed pods look like narrow beans.

Grow this plant in sun or part shade. Full sun brings out the strongest autumn leaf colour. Afternoon shade can extend flowering where the sun is hot. Too much shade can make the stems fall over. Rich soil can also weaken their upright form. It accepts clay, loam, sand and chalk with good drainage. Acid, neutral and alkaline soils all suit it. Moist soil supports growth, though plants tolerate some drought. Most US sources list USDA zones 5–8; Chicago includes zone 4. RHS rates its cold hardiness as H7.

Use bluestar in borders, rock gardens or open woodland plantings. Groups suit cottage, prairie, rain and pollinator gardens. Its fine leaves provide a backdrop for lower plants. Care needs are low, with few serious pest or disease problems. Deer tend to leave it alone. Cutting stems back after bloom can help keep clumps upright. RHS also advises cutting back in late autumn. Broken stems release milky sap that can irritate skin. The supplied sources give no evidence of edible uses.