How to Grow Amsonia Plants in your Garden

Gardener's HQ Guide to Growing Blue Star

The common name for the Hardy perennial Amsonia is blue star.

It typically flowers in the summer.

Some of the latin names include Amsonia hubrichtii, Amsonia tabernaemontana, and Amsonia hubrechtii. Common names include amsonia blue and star amsonia.

Thomas G. Barnes @ USDA-NRCS PLANTS Database / Barnes, T.G. & S.W. Francis. 2004. Wildflowers and ferns of Kentucky. University Press of Kentucky

Description of Blue Star

Amsonia Blue Star are attractive medium sized plants that can grow from 60 to 90 cm in height. As the name suggests Blue Star has blue star shaped flowers; these grow on long stems. these plants are ideal for beds that are located in the shade.

Blue Dogbane
Amsonia (Blue Dogbane) photograph by Dendroica Cerulea.

Amsonia Growing and Care Guide

  • Common Names: Blue star, Bluestars, Gray Amsonia.
  • Life Cycle: Hardy perennial.
  • Height: 8 to 36 inches (20—90 cm).
  • Native: North America, East Asia, Eastern Mediterranean.

  • Growing Region: Zones 4 to 9 (Amsonia hubrichtii 5—8).
  • Flowers: Late spring and early summer.
  • Flower Details: Pale blue, white, green. Clusters. Tubular. Flat faced stars. Five petals.
  • Foliage: Herbaceous. Woody. Linear to lance-shaped/ pointed ovals. Lower leaves wider than higher ones. Clump forming.

  • Sow Outside: Cover seed. Mid-spring or autumn.
  • Sow Inside: Germination time: four to six weeks. Peat pots. Temperature: 58 to 65°F (14—18°C). Start two to three months in advance. Transplant outdoors following any chance of a last frost. Space at 20 to 30 inches (50—75 cm).

  • Requirements and care: Shade for best colors, can tolerate full sunlight if soil is kept constantly moist. Regular watering during dry periods. Good drainage. Prefers a cool moist soil, but the type is not overly important. Slow growing. As stems can flop when grown in complete shade cut back to six inches (15 cm) following blooming. Propagate: by dividing in the autumn.

  • Family: Apocynaceae.
  • Closely Related Species: Adenium, Allamanda, Amsonia, Asclepias, Nerium, Pachypodium, Wrightia, Vinca
  • Miscellaneous: Named after John Amson, the American physician and Mayor of Williamsburg.
    Milky sap is a skin irritant (protects plants from slugs and snails).
    The European form (Amsonia orientalis) is commonly grown in gardens and is often wrongly named as Rhazya orientalis in garden centers and nursery’s.
    In Northern America the Arkansas blue star (Amsonia hubrichtii) is the most frequently grown species in gardens.
    Attracts butterflies. Deer resistant plant.

How to Grow Amsonia

It is best to sow Amsonia just below the soil surface, with a spacing of 50 to 75 cm in the middle of spring or the autumn.

Blue star prefers partly shady conditions, but can be grown in full sunlight as long as it is kept moist. The soil should be cool and moist. Amsonia requires between four and six weeks to germinate.

If growing indoors it is best to start seeds off nine to eleven weeks before planting outside in the late spring. Ideally they should be grown in peat pots at a temperature of 14 to 18 degrees centigrade when growing inside.

Caring for Blue Star and other Amsonia in the Garden

Amsonia plants requires light pruning and watering in the driest months of summer.