Heart-leaved American aster
September 2015

Tall, blue-violet-flowered aster of woodland edges and meadows; flowers profusely from late summer throughout autumn, in sun and partial shade; attracts late-season pollinators; found from Nova Scotia, west to Minnesota, south to northwest Alabama.

By Pamela Johnson

The Aster Family is one of the most populous in the world. Globally there are 1,300 genera of Asteraceae, and more than 21,000 species. In North America there are at least 120[1] asters with more than 54 indigenous to the eastern United States. The Asteraceae colonize 95 pages in Flora Novae-Angliae, the most current botanical manual for New England.

In Maine, Asteraceae (once called Compositae) include many of August’s and September’s most familiar wild flowers. Goldenrods and asters prevail in fields and meadows: swaths and swales of golden yellow, white, purple, magenta and blue unfurl in roadside tapestries. Henry David Thoreau wrote in his Journal, in August of 1853:

Why so many asters and goldenrods now? The sun has shone on the earth, and the goldenrod is his fruit. The stars, too, have shone on it, and the asters are their fruit.[2]

It is fortunate for insects, birds, and mammals that Maine has such a feast of flowers late in the season. Sustenance- nectar, protein-rich pollen, and seeds- is as important at this time of year for those preparing to migrate, hibernate, or actively face the approaching winter, as it was in spring for reproduction.

Asters have been juggled (some would say tortured) recently by taxonomists and the new nomenclature may seem unwieldy. Current aster genus names now include Doellingeria, Eurybia, Symphyotrichum, and Oclemena. Blue wood aster, once Aster cordifolius, is now Symphyotrichum cordifolium: same plant, new genus name in company with New England and New York asters (Symphyotrichum novae-angliae and S. novae-belgii), and calico asters (S. lateriflorum), all neighborly denizens of fields and woodland edges in the late-season landscape.

It is not necessary to learn all the new aster names in order to appreciate the wealth of flowers arrayed at this time of year. Learning some aster characteristics, however, is instructive, especially if one wants to use the plants in a garden setting. Those asters that grow naturally in deep shade, for instance, like large-leaved aster (Eurybia macrophylla) or whorled aster (Oclemena acuminata), have leaves either of a size or arrangement best adapted to capture limited sunlight. The foliage of large-leaved aster is outsize, blanketing the ground, and outcompeting nearby low vegetation. Whorled asters have slender leaves circling their stalks in eddies, tiers of leaves structured to compete less with each other. White wood asters (Eurybia divaricata) thrive in dryish shade where their numerous smaller leaves clasp zig-zagging stems that seem to scramble for sunlight.

John Eastman, in Forest and Thicket, describes the asters’ pursuit of light in this passage:

In woodland asters, there is a much greater proportion of stem and foliage to flower clusters, in contrast to the reverse situation seen in meadow asters. Such divergent ratios reflect the plant’s concentration of energy; in woodland asters the reproductive parts are less vital than the vegetative structures necessary to maintain their population stability in shaded forest environments.[3]

If the natural site of an aster does not immediately reveal a plant’s identity, there are plenty of other characteristics to be learned; and given asters’ tendencies to hybridize, field identification could occupy many seasons. Blue wood aster does not present much of a challenge compared to some of its kin; it does straddle different habitats, but its lovely form is easily recognizable.

Blue wood aster has cordate (heart-shaped) leaves, nicely toothed on their margins. Leaves diminish in size as they ascend the flower stalk. The leaves are deep green and ornamental. The flower stalks can be purpled by strong sunlight.

The flowering of blue wood aster is its glory, a cumulus-cloudlike flourish of pale blue, blue-violet or deep blue; flowers vary in color with different soil-types, moisture and sunlight levels. A colony of blue wood asters in full bloom looks like purple smoke or an ice-blue fog drifting across the ground.

Some of the other common names of blue wood aster are evocative: bee weed, blue devil, West Virginia stickweed, and, here in Maine, “tongue” (because the leaves were once cooked as a potherb.) The naturalist Constantine Samuel Rafinesque (1783-1840) noted in his encyclopedia of plants that blue wood asters’ roots were smoked to produce an incense, thought to attract deer by its mimicry of the odor released by a gland between the animal’s hooves.

Notwithstanding use as deer bait, North America’s appreciation of its own native asters is wan compared to that of British horticulturalists and gardeners. Several asters from Virginia were cultivated by John Tradescant (?-1638) and his son John Tradescant, Jr. (1608-1662) in their garden at Lambeth, near London. Both men had travelled to the New World, collecting seeds and specimens for their nursery. John Bartram (1699-1777), the American botanist, explorer and plantsman, sent asters to his aristocratic English subscribers, throughout the eighteenth century.

It was the revolutionary and transformative naturalistic plantings of William Robinson (1838-1935), particularly in his own garden at Gravetye Manor in West Sussex, England, that fixed American asters in the firmaments of English garden borders. In Robinson’s entry for “Asters” in The English Flower Garden (1933), he lists twenty-six garden-worthy asters of which fifteen, including blue wood aster, are from eastern North American. The entry says:

. . . asters are excellent for forming groups to cover the bare ground among newly planted shrubs. Nothing can be more easy to cultivate . . . There is quiet beauty about the more select starworts [asters], which is charming in the autumn days, and their variety of color, of form, and of bud and bloom is delightful. [4]

The popularity and ubiquity of American asters in the late-summer displays in English gardens, gave these asters the collective name Michaelmas daisies– for the archangel’s feast day celebrated annually in Britain on September 29th.

Because many asters manufacture great rafts of flowers, the plants feed pollinators still active even as the days shorten. Even in shade, blue wood asters produce an abundance of small flowers, upon a sturdy, tall flower stalk that branches pyramidally along its length. On a random five-foot stalk, I recently approximated 2,500 flower buds. Each flower, actually a ray flower with a sterile blue or violet corolla and a fertile yellow disk at its center, measures less than a half-inch in diameter. The aggregate, however, the entire inflorescence is an enormous food reservoir- one-stop shopping for nectar, pollen, and seeds while the flowers open gradually, and bloom for weeks. And the billows of flowers make blue wood aster one of the loveliest for gardeners to grow.

It is rare to see an aster in late summer not attended by insects searching for a final, rich source of fuel (nectar or pollen). Also, according to Douglas Tallamy and Rick Darke, blue wood aster persistently attracts 109 species[5] of caterpillars , the larvae of moths and butterflies (Lepidoptera). Some of the moths who prefer blue wood asters have beguiling names: Halloween paint (Cucullia alfarta), brown-hooded owlet (Cucullia convexipennis), the confused Euscara (Eupithecia confusaria), the common pug (Eupithecia miserulata), and the lost sallow (Euplexia devia).

There are five species of leaf beetle (Chrysomelidae), a long-horned beetle (Mecas purgata), leafminer flies (Agromyzidae) aphids (Aphidiae), lacebugs (Tingidae), walkingsticks (Diapheromeridiidae), plant bugs (Olividae), and leafhoppers (Cicadellidae) who dine on blue wood aster leaves. Yet the foliage rarely shows evidence of being a meal for so many. Blue wood asters’ foliage turns deep greenish purple or burgundy in October or November when goldfinches and chickadees crowd the flower stalks with their seed gathering acrobatics. Deer may browse Blue wood asters but the plants respond with renewed growth and enough flowers for everyone’s succor and pleasure.

Cultivation is very simple, as is seed harvest. When the seeds’ tufts appear and release from the plant when gently touched, they are ready to be collected (the white “parachutes” which will eventually send the seeds airborne). Seed should be air dried in a paper bag for several weeks for after ripening. Seeds can be sown out of doors in the late fall or spring, and do not require cold stratification to germinate. However, germination is improved with cool, fluxuating weather provided by outdoor sowing.


[1] Asters numbers vary widely because there are many natural hybrids (subspecies). Britton and Brown list over 200 North American asters.
[2] Loewer, Peter. 1996. Thoreau’s Garden. Mechanicsburg, PA: Stackpole Books.
[3] Eastman, John. 1992. Forest and Thicket. Mechanicsburg, PA: Stackpole Books.
[4] Robinson, William. 1984. The English Flower Garden. Sagaponack, N.Y.: Sagapress, Inc.
[5] Tallamy, Douglas and Rick Darke. 2014. The Living Landscape. Portland, Oregon: Timber Press.