April Plant of the Month: Amsonia

Amsonia, as a genus, consists of approximately 20 species that occur in light woodlands or grasslands in Southeast Europe, Turkey, Japan, and Central and Northeast United States.

Like their close relative milkweed, amsonias also exude a milky sap they when scored. Toxic compounds in the sap make them unpalatable to insects, though their pretty blue starlike blooms are attractive to butterflies, including the zebra and other swallowtails. Like milkweed, their seedpods split open to release seeds.

Shining blue star, Amsonia illustris, is one of three amsonias native to Missouri. The others are willow amsonia, A. tabernaemontana and fringed blue star, A. ciliata. All are known for their striking bunches of small five-petaled blue blooms at the ends of their stalks in April and May.

Amsonias are easy to grow in full sun to part shade though, a bit sprawling, they may need staking when not grown in full sun. They can be pruned back by up to half after blooming to promote bushy, compact growth, though the four-inch seedpods do add visual interest.

A. illustris, which grows two to three feet, features clusters of ½ inch blue, star-like bloom clusters in April and May that turn to thin, erect seedpods atop the plants. Its shiny, narrow leaves resemble leathery willow leaves. Like all amsonias, its leaves turn a beautiful yellow in fall. Plants can be viewed in the Ellis Perennial Garden, and on the east sides of Lafferre and Stewart Halls.

A. tabernaemontana, closely resembles A. illustris but with ¾ inch light blue blooms, thicker, less shiny leaves and seed pods that are more pendant. Two noteworthy hybrids are 'Starstruck' a more compact version growing to 2 feet, and ‘Storm Cloud' that features dark stems and silver-veined dark green leaves in spring.

Discovered growing near A. tabernaemonta seedlings at Connecticut Botanical Garden White Flower Farm, 'Blue Ice' is a more compact version with ¾ inch darker blue blooms. Its parentage has not been definitively determined. It is growing near the Journalism complex.

A less common Missouri native is A. ciliata, which features much finer leaves and occurs in sandy soils in the wild.

Arkansas’s Amsonia
Native to the Ouachita Mountains in central Arkansas, Amsonia hubrichtii is commonly known as threadleaf blue star or Hubricht's blue star and looks very much like A. ciliata with even finer, thread-like leaves and powdery blue, ½ blooms atop 3-foot plants. It can be found in the Ellis Perennial and on Carnahan Quad.