Tempt More Wildlife Into Your Garden by Growing Autumn Asters

Just when the last goldenrods peak and other summer flowers are but a memory, autumn asters offer a last burst of blooms. You may notice them as little white or blue flowers along a woodland trail, or perhaps you see a towering purple aster leaning against a fence in a cottage garden. Look closer and you will see that the plants are abuzz with bees, beetles, hoverflies and butterflies on a sunny day. As the last native flowers to bloom in much of North America, autumn asters are hugely important to bees and other pollinators in search of a last meal.

Within the huge aster family, the hundred or so fall-blooming aster species native to North America are mostly placed in the Symphyotrichum genus (pronounced sim-fy-oh-TRY-kum), often called “Symphs” in plant circles. They are different from asters from Europe and Asia, which are not nearly as keyed into the short days of fall. Most start blooming in October and keep going through the first frosts, which is why they are often called Michaelmas daisies. Michaelmas is the old term for the season that starts on September 29, with the Feast of the Archangels, and continues to Christmas.

The Importance of Autumn Asters

Autumn asters are considered keystone plants because of their importance to wildlife, especially as a floral resource for pollinators late in the season. Before that, young shoots are nibbled by rabbits and deer, resulting in natural pruning, and in summer the plants host larvae of pearl crescents and several other butterflies. The blooms provide nectar and pollen to pollinators that are active on warm autumn days, as seen in this video of butterflies on aromatic aster at Dyck Arboretum near Wichita Kansas on October 22, 2024. From winter through spring, wild birds eat the seeds.

In the wild, most autumn asters prefer the partial shade of woodland edges, and they thrive in mixed wildflower meadows or cultivated gardens. These days, wild asters may be in decline because of invasive plants challenging them for space, over-grazing by deer in areas with high deer populations, and perhaps being outcompeted by more aggressive native goldenrods. Last summer, the US Botanic Garden Washington DC added six more species to their pollinator garden. Maybe you should, too.

Nifty Native Asters

Any of the native autumn asters can be grown from seed (keep reading) or you can start with a plant purchased from a nursery. Shop local native plant nurseries first, because they may have the species best suited for your area. Most named varieties are “nativars,” or selected native plants that are adopted for cultivation and then propagated vegetatively to maintain genetic uniformity. They have not been hybridized and may be sold by species name. Mail order nurseries offer plenty to choose from. In the UK, Beth Chatto Gardens has introduced a dozen deserving autumn asters to English gardeners. In the US, Bluestone Perennials is a good source for October Skies and other popular strains. Plant Delights nursery offers distinctive nativars that are adapted to warmer climates.

Autumn Aster Growing Tips

Autumn asters are easy to grow from seeds, which benefit from chilling and are great candidates for winter sowing. Or, simply chill seeds in damp sand in the refrigerator for three weeks before sowing in early spring.

It’s much easier and faster to propagate asters vegetatively. If a friend or neighbor has a plant, simply wait until spring and arrange to take two or three 6-inch (15 cm) stem cuttings from near the base of the plant. These should root nicely in two weeks. With species that form colonies, you also can also dig root divisions from an established clump and replant them immediately. Either method will produce vigorous plants that bloom their first year.

To promote bushy growth, pinch back the primary growing tips in early summer, but not after the summer solstice. With tall growing New England asters, provide a sturdy trellis to keep plants upright; most other fall asters prefer to sprawl.

Though asters are considered animal resistant, the young growth may be eaten by rabbits and deer. Protect young plants from browsing with chicken wire cages. Aromatic aster (S. oblongifolium) is less appetizing to hungry animals.

Wild plants require no pruning. In the garden, allow the plants to hold their branches through winter, which shelters the root zone and accommodates doves, juncos, sparrows and other ground-dwelling winter birds. When new growth appears in spring, prune out dead branches and up to one third of the growth of woody species. Smaller types die back to the ground in winter and can be cut back to stubs.

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