University
of Vermont ExtensionDepartment of Plant and Soil Science
University
of Vermont Extension
Common name: Blue Stars, Blue Star Flower, Willow Amsonia
Family: Apocynaceae, Dogbane
Height x Width: 1-3' tall x 3' wide
Growth Rate: slow to moderate clumps
Foliage: alternate, entire, hairy depending on species.
Flowers: variously blue depending on species, star-shaped, bisexual, in terminal panicles in early summer
Hardiness: Zones 3-9, depending on species.
Soil: moderately fertile soil, highly fertile soil causes the plant to fall over; moisture preferance varies with species, but generally well-drained, moist.
Light: full sun to partial shade
Pests & Problems: none serious
Landscape Habit, Uses: massed in borders, natural plantings, adds a lovely blue color to the front or middle of the border, golden yellow foliage in fall.
Other Interest: Genus was named for Dr. Charles Amson, an 18th century scientific traveller in America. Fruit are long, narrow pods (follicles), erect or otherwise depending on species. Plants, as many in this family, with milky sap.
Other Culture: tolerant of many conditions, cut back in fall, and cut back after flowering if in shade to prevent falling over, divide in 8-10 years, otherwise low maintenance.
Propagation: division in spring, soft stem cuttings in early summer with rooting hormone, seed. Seeds require a cold stratification period of 4-6 weeks and/or soaking overnight before they will germinate.
Sources: many including specialty perennial nurseries; Perennial Pleasures Nursery (VT), We-Du Nurseries, Niche Gardens among other mail order sources