For fall fireworks, it’s hard to beat asters. With the starry flowers for which they’re named (aster means star in Greek) and wide range of colors, they are a reliable source of flower color when changing leaves are stealing the show.
(Side note: The genus Aster has been renamed Symphyotrichum. But aster is a more common name, so we’re sticking with it for this post.)
Choices for Indiana Gardens
Aster oblongifolius (AKA Symphyotrichum oblongifolium) is an Indiana native. And according to a study done at Chicago Botanic Garden, it’s the best choice for the Midwest garden. These plants have fine, sky-blue petals on stiff stems. They grow from about 1′ to 3′ tall and are fragrant when crushed (hence their common name, aromatic aster). In the nursery, you’ll find the cultivars ‘October Skies’ (about 18″ x 24″) and ‘Raydons Favorite’ (about 36″ x 24″).
An Indiana native more common in garden centers is the Aster novi-angliae (Symphyotrichum novi-angliae), or New England aster. It’s available in a wide range of colors, from brilliant pinks to light blues to purples. We prefer to plant it toward the back of the border, because it often loses leaves on the lower stems. You can find cultivars in heights of 12″ to 36″. We’ve done well with ‘Purple Dome’ and ‘Vibrant Dome.’
New York aster (Aster novi-belgii or Symphyotrichum novi-belgii) is native to the east coast and only so-so in Indiana. It can have trouble with the winters in the northern part of the state, so plant it in a sheltered location if you can.
While most asters prefer full sun, the wood aster (Aster divaricatus, now Eurybia divaricata) is a great choice for the part-shade garden. Its flowers are relatively small.
Asters timed to bloom in the nursery and sold for fall color in pots do not tend to do well when transplanted. Instead, plant in the garden in late spring or in September. Asters will normally bloom in late summer to early fall.
Most asters prefer full sun and well-drained soil. To get the best performance out of them, don’t plant them in a rich soil or fertilize them; they’re likely to flop. To delay bloom, start cutting them back by about 1/3 in late spring (we use a pair of shears). Keep cutting until mid-July. You’ll get a bushier, fuller plant and more blooms.
We love putting asters into mixed borders to continue the show through fall. They work especially well with other butterfly plants like coneflower, daisy, and joe-pye weed (Eupatorium spp.), which prefer the same full sun and lean soil. They are also gorgeous when mixed with other standouts of the late summer and early fall, like Caryopteris and beautyberry (Callicarpa spp.).