Bluestar or Amsonia is a herbaceous perennial that is a favorite of gardeners in spring and fall.
They are hardy, disease-free perennials with pale blue, star-shaped flowers in spring. Flowers are loosely arranged in terminal cymes for 2-3 weeks in late April or May. The narrow, dark green leaves are disease-free and become the backdrop for other smaller perennials in the summer. But in fall, the plants take center stage again as the leaves turn a brilliant, golden yellow. While many perennials are noted for their blooms, few offer reliable fall color like bluestar.
Culture
Bluestars are easy to grow as they are adaptable to many sites and soils. They prefer part shade, but also do well in full sun. Bluestars prefer fertile, well-drained soils, but will tolerate heavy clay soils and dry soils once established. Different species prefer different degrees of soil moisture, with Amsonia tabernaemontana preferring moist soils and A. ciliata and A. hubrichtii preferring drier soils.
Occasionally, plants will be floppy, especially in shady sites. Established plants can be cut back by half after bloom for shorter, more compact habits. The crown and root system of many bluestars is dense and can be difficult to divide or move once established.
Deer avoid bluestars as they produce a potentially toxic milky sap, like many members of the Apocynaceae family (dogbane family) that include vinca, milkweed, and oleander.
Species
There are approximately 20 species of Amsonia, and all but 2 or 3 are native to North America. The most commonly cultivated species are native to the Southeastern US (A. tabernaemontana), central Missouri (A. ciliata), or the Ouachita Mountains in Arkansas (A. hubrichtii). Most bluestars are cold hardy to zone 5, except A. rigida (native coastal Georgia and Florida), which is listed as zone 6 hardy.
| Scientific name | Common Name | Size (ft) (H x W) | Leaf texture | Comments |
|---|---|---|---|---|
| Amsonia ciliata | Fringed bluestar | 2-4 x 3-5 | fine | Leaves wider than hubrichtii |
| Amsonia elliptica | Japanese bluestar | 1-3 x 3 | Medium-coarse | Rare in cultivation; variable habits |
| Amsonia hubrichtii | Hubricht’s bluestar | 3-4 x 3-5 | fine | Narrow leaves; reliable fall color |
| Amsonia rigida | Stiff bluestar | 2-4 x 3-4 | medium | Zone 6 hardy |
| Amsonia orientalis | European bluestar | 1.5-2 x 3-6 | medium | Spreading habit |
| Amsonia tabernaemontana | Eastern bluestar | 2-4 x 3-5 | medium-coarse | Widest leaf; variable fall color |
Varieties and Cultivars
There are several varieties, cultivars or hybrids of bluestars available at local garden centers.
For more compact habits, consider A. ciliata ‘Georgia Pancake’, which only reaches 9-10 inches tall, or A. ciliata ‘Spring Sky’, which stays below 2 feet.
Compact cultivars of Amsonia tabernaemontana ‘Fontana’ grow to approximately 3.5 feet, and ‘Storm Cloud’ only reaches 2.5 feet tall.
‘String Theory’ is a compact hybrid of A. hubrichtii, only growing to 2 feet tall.
‘Blue Ice’ is a selection of A. orientalis that grows to approximately 15 inches tall. European bluestar, however, spreads via rhizomes once established.