Aster

About Aster

Fall asters are the purple, blue, pink and white daisies that light up the garden from late summer until hard frost. New England and New York asters are native to eastern North America and were moved from Aster to Symphyotrichum after DNA studies (Illinois Extension); Frikart's aster is a European-Asian hybrid that starts blooming in early summer. Late bees, hover flies and migrating monarchs lean on them, and New England aster feeds pearl crescent caterpillars.

Mt. Cuba lists New England aster for zones 3-8 and NC State lists New England and New York asters for 4-8; Frikart's aster is hardy only to about zone 5 and needs sharp winter drainage. A few asters spread fast by rhizomes (Chicago Botanic Garden), but we found no invasive listing for these species in the US.

When to plant

Timing is counted from your average last spring frost (and first fall frost). Sow & Tell works out the actual dates for your ZIP code.

Most people set out potted plants in early spring or fall; finish fall planting at least 6 weeks before the ground freezes hard (Clemson). For seed, press it onto the soil in late fall without burying it, since winter cold helps it sprout in spring (UVM); NRCS says spring-sown seed germinates better after chilling.

Soil

Moist, fertile, well-drained soil, including clay loam (NC State); Frikart's aster needs excellent drainage, especially in winter (Piedmont Master Gardeners).

Work compost into moist, well-drained soil (clay loam is fine); Clemson aims perennial beds at pH 6.0-6.5. Follow a soil test.

Feeding

• early spring, just before new shoots come up (optional; many asters need none): slow-release fertilizer such as 12-6-6, or a 1-inch layer of compost. Feed sparingly: Kentucky Extension says New York asters need little, and Chicago's trial asters got no fertilizer. Clemson's general rate for perennial beds is 1-2 lb of a slow-release 12-6-6 per 100 sq ft just before shoots emerge; MSU advises no more than 1 lb of nitrogen per 1,000 sq ft. Scatter it around the plants and water it in. Follow a soil test.

Too much fertilizer makes tall, floppy stems (MSU). Crowded clumps get more powdery mildew, so divide every 2-3 years and thin stems for air flow (Chicago Botanic Garden; Kentucky; Illinois).

Harvest

New England and New York asters bloom from August or September into October or later; Frikart's aster starts in June or July. Pinch stems a few times before mid-July (Mt. Cuba) or shear to half height in early June (Chicago Botanic Garden) for shorter, sturdier plants. Cutting stems after bloom limits self-seeding.

Varieties (27)

Good neighbors

Goldenrod

NC State suggests pairing New England aster with fall-blooming goldenrod for a showy fall display; this is a design pairing, not a pest-control companion.

Pests to watch for

Aphids, Twospotted spider mite, Leafminers, Deer, Rabbits, Leafhoppers, Annual cicadas (dog-day cicadas), Lace bugs (azalea and chrysanthemum lace bugs)

Diseases and problems

Powdery mildew, Rust, Aster wilt, Stem rot, Southern blight, Aster yellows

In the kitchen

Safety: The sources we checked list no toxic parts for these asters and no research-based guidance on pregnancy, drug interactions or allergies.

Pets: Not listed by name by the ASPCA (true asters, Symphyotrichum). The ASPCA's 'aster' entries are China aster (Callistephus chinensis), which it calls non-toxic to dogs, cats and horses, and giant aster (Townsendia sericea), listed as non-toxic to dogs, cats and horses.