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Flat-topped aster is a good midsummer to early fall native addition to a pond, wetland area, or rain garden. The small, daisylike flowers are white with yellow in the center. They look best when planted in colonies, but they can be a bit unkempt. Flat-topped aster is effective at attracting pollinators. This species is native to the Chicago region according to Swink and Wilhelm’s Plants of the Chicago Region and current research.

  • Family (English) Aster
  • Family (botanic) Asteraceae
  • Tree or plant type Perennial
  • Native locale Chicago area, Illinois, North America
  • Size range Large plant (more than 24 inches)
  • Light exposure Full sun (6 hrs direct light daily), Partial sun / shade (4-6 hrs light daily)
  • Hardiness zones Zone 3, Zone 4, Zone 5 (Northern Illinois), Zone 6 (City of Chicago), Zone 7, Zone 8
  • Soil preference Acid soil, Moist, Wet soil
  • Tolerances Occasional flooding, Wet sites
  • Season of interest midsummer, late summer, early fall
  • Flower color and fragrance White, Yellow
  • Shape or form Irregular, Narrow, Upright
  • Growth rate Fast
  • Wildlife Birds, Butterflies, Insect pollinators

Size and method of spreading:

Flat-topped aster self-seeds and spreads by means of rhizomes. Plants are typically 2 to 5 feet tall and 2 to 4 feet in width. 

Native geographic location and habitat: (include C-value if appropriate)

Flat-topped aster is native to the Eastern and North Central United States. C-value: 8.

Attracts birds or pollinators: 

Flat-topped aster attracts various species of bees and wasps, as well as pollinating flies, beetles, and skippers. Bees that are specialist pollinators of flat-topped aster include Andrena nubecula, Andrena placata, Perdita octomaculata, and Pseudopanurgus andrenoides. Flat-topped aster is also a primary host of Harris’ checkerspot butterfly (Chlosyne harrisii). The seeds are eaten by American tree sparrows and ruffed grouse, with the latter also browsing on the leaves. 

Leaf description:

The leaves of flat-topped aster are often between 3 to 6 inches long and one-half to 1 inch wide, with the smallest leaves located at the bottom of the unbranched stem. Leaves are attached directly to the stem (sessile) and are long and narrow with a slightly wider and rounded base (lanceolate-elliptic or elliptic). The edges of the leaves are toothless (entire). 

Flower description:

The small daisy-like flowers consist of 5 to 12 petals (ray flowers) around the center (12 to 25 disk flowers). The ray flowers are white and irregularly spaced. The disk flowers are yellow, but mature to a duller, creamy, almost white as the bloom fades. Each flower head is approximately one-half to three-quarters of an inch across. The base of each flower head has awl-shaped bracts that occur in three to four layers. The only branched portions of flat-topped aster are the stems of the flowers, with the lower flower stems longer than the upper stems of each group of flowers, giving the groups the appearance of a flat-top (compound corymb). 

Fruit description:

Like other species of aster, the fruit of flat-topped aster are small, dry, and attached to whitish hair tufts (achenes) that allow the wind to carry them. Unique to flat-topped aster are the unevenness of the hairs attached to the fruit, with the outermost hairs shorter and the inner hairs longer.

Plant care:

Flat-topped aster does not like to dry out, so make sure to plant in an area that will maintain some moisture. They can spread somewhat rapidly via rhizomes, and may self-seed slowly as well, so some division may be necessary to prevent overcrowding. Deadheading can reduce self-seeding. 

List of pests, diseases, and tolerances:

No major diseases or pests are issues for flat-topped aster.


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