In the Garden: Symphyotrichon

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Climbing Aster growing to six feet on a trellis. Photo: Charles Kidder.

A rose by any other name would smell as sweet, according to Shakespeare. But what about a Symphyotrichon?

Symphyotrichon is just one genus of perennial plant commonly referred to as Asters in the United States, and as Michaelmas Daisies in the U.K. Until a few years ago, there were almost 600 species of aster, sharing the same scientific and common names in our part of the world. In the late nineties, research revealed some significant differences among these species, whereby there are now only about 180 species of “true” asters, i.e. the scientific name of the genus remains as Aster.  Several hundred other species were split off into new genera, with delightful names such as Eurybia and Symphyotrichon. Sometimes referred to as the Aster Disaster, this renaming was particularly bothersome to those in the business of selling—or buying—plants. To this day, some nurseries still list their plants as asters to keep things simpler for their customers.

Regardless of nomenclature, asters deserve a place in every garden. When most other perennials are done for the year, asters are just beginning to hit their stride in the fall. While a few start to bloom in August, peak color is typically in September to October, and some species hang on into November.

In something of a reversal of the usual horticultural situation, the native American asters are more commonly grown in eastern U.S. gardens than their Asian cousins. The genus Symphyotrichon comprises thirty-some species native to Virginia, and a few of those are garden stalwarts; the New York Aster (S. novi-belgii) alone includes more than forty cultivars of varying dimensions and flower color. ‘Autumn Rose’ stands a statuesque 48 inches, with rosy-pink flowers. ‘Crimson Brocade’ has flowers of the hue that the name suggests, and tops out at around 36”. Almost a ground cover, ‘Apollo White’ reaches a height of only ten inches.

The New England Aster (S. novae-angliae) is common in the Ridge and Valley province of Virginia, as well as in the western Piedmont. The cultivar ‘Alma Potschke’ is fairly tall at 48” and requires staking to prevent flopping; flowers are rose-pink. As with most asters, cutting the plant back to half its height in mid-June will produce a more compact plant. ‘Purple Dome’ is covered in a mass of bright purple flowers and tops out at only 24”. A word of warning on the New England Asters: I’ve seen one report that the hairy stems can produce a rash.

A couple of compact cultivars of the Side-Button Aster (S. dumosum), aka Rice-Button Aster or Bush Aster, are tough garden plants. With red-violet flowers, ‘Alert’ grows to only 18” tall and as wide. ‘Danielle’ grows to one foot; flowers are deep violet.

Small needle-like leaves lend the Heath Aster (S. ericoides) its common name. ‘Pink Cloud’ is mildew-resistant and grows to about three feet. Covered with larger white flowers, ‘Snow Flurry’ reaches only a foot in height. Smooth Aster (S. leave) ‘Bluebird’ arrays its violet-blue flowers on arching stems that can grow to about forty inches. Reportedly, no staking is required for this variety. In Virginia, Smooth Aster grows primarily on calcareous soils in the mountains.

Something of an oddball among its genus, Climbing Aster (S. carolinianum) is a shrub that sends its stems arching over any support it can find. In my garden, this Deep South native has reached six feet growing over a couple of trellises. Pinky-lavender flowers appear in late fall and are covered with pollinators.

Moving on to another genus, the White Wood Aster (Eurybia divaricatus) is notable for tolerating shade, although morning sun plus good air circulation will provide the best flowering and yield a healthier plant. Only growing to about two feet, it will be covered with a cloud of small white flowers in late summer into fall.

A couple of Asian asters are worth mentioning. With its strong spreading habit, Japanese Aster (Aster ageratoides ‘Ezo Murasaki’) will form a two-foot tall ground cover topped by medium-purple frost-resistant flowers. It needs a fair amount of water and shouldn’t be placed near other plants. Another spreader is the Tatarian Aster (Aster tataricus), growing to near six feet and requiring no staking; light blue-purple flowers appear in mid-fall. The variety ‘Jindai’ stays slightly smaller and spreads more slowly. The Tatarian asters resemble a mound of chard until they send up their flower stalks, not exactly refined, so you should consider hiding the base among some other plants.

Some general cultural requirements for all the asters: although most can tolerate some dryness, moderate moisture is best. Except for the White Wood Aster, most are happiest with a lot of sun and good air movement. Depending on how much flopping you’re willing to accept, most will look better if cut back by half in mid-June. Or be prepared to stake them up.

By the way, all asters that we’ve looked at have flower petals that range all the way from white to crimson, with blue, purple and pink in the spectrum. Typically the centers are yellow, but none have totally yellow flowers. The Maryland Golden Aster (Chrysopsis mariana) has golden flowers, but it’s not really an aster. At least not for the time being.

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