Blooming late summer through frost, asters (Aster or Symphyotrichum spp.) color beds, borders and containers. The Aster genus includes about 250 species and numerous cultivated varieties and hybrids. Most are characterized by fairly narrow leaves and daisylike flowers ranging from white through blue, purple and pink. The best garden asters are relatively pest and disease free and suit both the site and the specific U.S. Department of Agriculture plant hardiness zone.
New England Asters
New England asters (Aster novae-angliae or Symphyotrichum novae-angliae) are tough native perennials, hardy in USDA zones 5 through 8. Descended from meadow-dwelling plants, they are generally 3 to 6 feet tall with somewhat hairy leaves. Mature specimens are covered with scores of daisylike flowers. Among the best New England aster varieties is "Harrington's Pink," a tall variety with rosy pink flowers that scored a four-star (good) rating in the Chicago Botanic Garden's comprehensive six-year aster trial. "Honeysong Pink," with deeper pink flowers, received the same high score.
New York Asters
New York asters (Aster novi-belgii or Symphyotrichum novi-belgii) are another group of native perennial asters that bloom reliably, increase year after year and are generally hardy in USDA zones 4 through 8. "Blue Lagoon," a dwarf variety, tops out around 18 inches tall and features blue or blue-purple flowers. A vigorous grower, it was chosen for inclusion in the Missouri Botanical Garden's plant collection. "Fellowship" won the Royal Horticultural Society's Award of Garden Merit in 2004. It grows up to 4 feet tall and bears large, double, pink flowers.
A hybrid aster, "Monch" (Aster x frikartii "Monch"), was the winner of the AGM in 1993. Hardy in USDA zones 5 through 8, "Monch" grows about 30 inches tall and produces large quantities of medium blue or blue-purple flowers with yellow centers. Another AGM winner, "Little Carlow" (Aster x cordifolia "Little Carlow"), stands even taller, up to 48 inches high, and has a wider hardiness range of USDA zones 4 through 9. Like "Monch," "Little Carlow" bears blue-purple flowers.
Asters require a sunny exposure and are not fussy about soil. Many of the best varieties, like "Harrington's Pink," have a strong tendency to self-seed, which can be either a blessing or a curse for gardeners. To discourage self-seeding, remove spent flower heads promptly when they begin to fade and watch for stray seedlings in the spring. Many asters have a susceptibility to powdery mildew, a fungal disease
that is a particular problem in humid weather. Maintaining proper planting distance to promote good air circulation and favoring drip irrigation instead of overhead watering help combat powdery mildew.
- The Botanical Garden: VII, Perennials and Annuals; Roger Phillips and Martyn Rix
- American Horticultural Society Encyclopedia of Plants and Flowers; Christopher Brickell, Editor-in-Chief
- Missouri Botanical Garden: Symphyotrichum Novae-Belgii "Blue Lagoon"
- Missouri Botanical Garden: Symphyotrichum Novae-Angliae
- Royal Horticultural Society: Aster "Little Carlow"
- Royal Horticultural Society: Aster x Frikartii "Monch"
- Royal Horticultural Society: Aster Novi-Belgii "Fellowship"
- Chicago Botanic Garden: Plant Evaluation Notes -- A Comparative Study of Cultivated Asters
- Photo Credit Ablestock.com/AbleStock.com/Getty Images