Autumn brings to mind the crisp, crunching sound of leaves underfoot, meadow grasses casting a golden hue over the once green fields, and roadsides dotted with brilliant goldenrods and vibrant pink and purple asters. Not having very much fall color in my childhood backyard, oh how I loved the thought of cutting bouquets of cheerful asters for my room – that is until I discovered that those large black and yellow garden spiders were as attracted to this plant as I was! Better to just leave Mother Nature alone.
Field of goldenrod. Photo by dmp, UConn
Asters used to be easy. There were over 600 species of them until molecular and morphological research in the 1990s determined there weren’t. Taxonomists pretty much divided the lot into New World and Old World species but kept them in the Asteraceae family. New World asters were put into new genus’ with tongue twisting names like Almutaster, Canadanthus, Doellingeria, Eucephalus, Eurybia, Ionactis, Oligoneuron, Oreostemma, Seriocarpus and Symphyotrichum. Now there are about 180 species in this group. Fortunately, all these plants are still referred to as asters making them easier to ask for when looking to purchase some new additions to your garden beds.
Double asters on picket fence. Photo by dmp, UConn
The European Michaelmas daisy remains an aster (A. amellus). According to Dr. Allan Armitage’s Herbaceous Perennial Plants, the original species is infrequently encountered but numerous cultivars have been bred and selected for. Despite the fact that many species of plants in the aster family are native to North America, much breeding was done in England and Germany beginning in the 1890s.
In the United Kingdom, many species we commonly think of as asters are called Michaelmas daisies. The feast of St Michael and All Angels falls on September 29th as the days shorten and nights grow longer. It is written that St. Michael was an archangel who fought against Satan and protected believers during the dark nights. The celebration of this feast occurs during the asters’ bloom time, hence their nickname Michaelmas daisies. Asters are also one of the birth flowers for September.
St. Michael from http://www.brittanica.com
The flowers of an aster are simple yet beautiful. They resemble daisies with their central yellow disk florets and their purple, pink, blue or white ray florets. The word, aster, means ‘star’ in Greek, most probably named for its rayed flowers. Pollinators flock to these plants. Native bees are continuously collecting pollen and the later blooming ones are especially sought after by both migrating and resident butterflies.
Aster visited by native bee. Photo by dmp, UConn.
Two types of asters most commonly found in our New England gardens are the New York aster (Symphyotrichum novi-belgii) and the New England aster (S. novae-angliae). In the wild, both species prefer sunny, moist areas but cultivated hybrids are perfectly content when planted in your average well-drained soil. Cultivars prefer being kept moderately moist during active growth periods but resent soggy soils when dormant. These unnamed asters were purchased at a garden club plant sale. The purple variety seems far more vigorous than the pink one these days.
Asters in bird house garden. Photo by dmp, UConn
Another interesting native aster is Eurybia divaricata, the white wood aster. The stems may reach 2 to 3 feet but they typically are a bit zig-zaggy and flop over so it looks like plants are only 18 inches high. The blossoms are small but many and the leaves are coarsely toothed and heart-shaped. White wood asters serve as a host plant for caterpillars of the pearl crescent and checkerspot butterflies.
Pearl crescent from http://www.wisconsinbutterflies.org
A second great attribute of this plant is that it grows in dry shade. I have it both in my white garden under a Clethra barbinervis and 2 ‘Bridal Wreath’ spireas and also in Treebeard’s garden under a Sawara cypress mixed in with ferns, epimediums and vinca. White wood asters thrive in both and multiply in a contained manner.
White wood aster. Photo by dmp, UConn
For a spectacular back of the border show, the Tatarian aster (Eurybia sibirica) cannot be beat. Growing to a height of 7 to 8 feet, the plants are covered with sprays of large, bluish, daisy-like flowers starting in late September and lasting well into October. Tatarian asters will spread rapidly I quickly learned after a gardening friend gave me an innocuous looking pot full. And, they are quite drought tolerant. Staking is usually not necessary if grown on the dry side. This year because of all the rain, they have grown quite tall and might need something to hold them up.
Tatarian aster with bees. Photo by dmp, UConn
Dwarf asters used to be more available. These are usually crosses between two or more species. I had a cultivar called ‘White Opal’ growing in my white garden for almost a decade. It was so delightful because clear white flowers opened on 8 to 10 inch stems. It died out during a particularly warm and wet winter and I have been unable to find it for sale either online or at local garden centers.
Standard varieties of asters are generally sheared at the nursery to produce more compact plants or growth regulators are used. Then in year two in your garden, the delightful, once 14-inch high bushy plants send up stems 3 or more feet tall completely disrupting your design. Asters, for the most part, have a tendency to be somewhat loose, rangy perennials.
Tatarian aster, zebra grass flower heads and purple smokebush make a fine late autumn display. Photo by dmp, UConn
If you prefer more compact plants, late blooming varieties can be pinched twice, once in mid-May and again in late June. Otherwise, plan on staking the plants early in the season or position them so their sprays of blossoms have another plant or object to lean over. Pinched plants also send out side shoots so you get more blooms.
Asters grow in full sun to light shade. Fertilize them lightly each spring. Excess nutrients have been implicated in disease problems. Rapidly growing asters need to be divided every third year as the center of the clump often dies out. As with other fall blooming perennials, division is best done in the spring. Dig up the whole clump and divide the outer portion into groups of 3 to 5 stems. Discard the old woody center. Replant divisions at 18-inch intervals. Pot up extras to donate to plant sales.
As with garden phlox, it is advisable to remove spent blossoms. Seedlings are often more vigorous than parent plants and will crowd out choice selections.
The only real problem I have encountered with asters is their susceptibility to powdery mildew. Keeping them well spaced and divided to increase air circulation usually keeps this fungus problem under control. Some varieties are bred for resistance to this disease.
Asters make wonderful additions to perennial beds and borders, and are suitable for naturalizing. They will surely be as much of a star in your fall gardens as they are in mine.
Dawn P.
Uconnladybug's Blog 