September 2023: Asters
Asters and goldenrods, Part 2.
These two standouts of the late-summer and autumn landscape give new meaning to the oft-repeated garden design phrase “four-season interest,” but from the point of view of our treasured pollinators and songbirds. Late September into October is a good time to plant them, until the temperature drops below freezing at night.
Questions or comments? Write to Homegrown Habitat columnist Sarah Middeleer at email@example.com.
The nectar of goldenrods and asters nourishes migrating butterflies such as painted ladies and monarchs, and their pollen feeds a great number of native bees. Once their colorful flowers have faded, birds and rodents rely on the resulting seeds. The well-fed rodents then help to nourish raptors through the winter. Many beneficial insects establish winter homes inside the left-over stems (so try to leave them uncut despite the urge to complete a “fall clean-up”).
Douglas Tallamy, entomologist and author, has called asters and goldenrods, as well as native sunflowers, “keystone herbaceous plants for attracting beneficial insects.” His website homegrownnationalpark.org states, “Landscapes that do not contain one or more species from keystone genera will have failed food webs, even if the diversity of other plants is very high.” The concept of food webs is fundamental to understanding ecologically oriented gardening, because it points out the critical connections between soil microorganisms, plants, insects, birds, and other wildlife.
Native asters have something to offer everyone, ranging in bloom color from white to pale blue, rose and violet, and growing from six inches to six feet high. The wood asters take shade, while many of the others grow best in full sun. Like goldenrods, asters typically adapt to different soil conditions, but many asters will be happiest in moist soils.
Asters have been highly bred, resulting in numerous cultivars (or “nativars”). Not all cultivars are as attractive to birds and pollinators as the straight species. One can tell when a plant is a cultivar when its nametag presents a second name in single quotes, such as New England aster ‘Purple Dome.’ For example, this cultivar’s flowers are darker purple than those of the straight species. Research has shown that pollinators visit nativars with different flower colors less frequently than they visit the straight species. So, for the sake of wildlife, try to use as many straight species as possible, depending on your available gardening space and local availability of native plants.
Here are a few native asters that might be suitable in your landscape, along with potential goldenrod companions.
New York aster (Symphyotrichum novi-belgii)
With upright, clumping habit, New York aster grows three to four feet high. Purple (or pink or white) petals surround yellow centers. It prefers sun with moist but well-drained soils. New York aster will be a good companion for sweet and showy goldenrods. Together, these large plants may be best in naturalized areas or at the rear of the border.
New England aster (Symphyotrichum novae-angliae)
Clump-forming with stiff stems, New England aster grows to six feet or more. Its purple and yellow flowers are favored by migrating monarch butterflies. New England aster prefers sunny, moist sites. Combine it with showy goldenrod and New York ironweed for colorful, late-summer bloom sequence in a moist meadow. Canada goldenrod will reach almost as high as this aster but is so aggressive that it will, alas, take over–and is thus not recommended for any but the largest of meadow landscapes.
Stiff-Leaved Aster (Ionactis linariifolia)
In contrast to many other asters, the petite stiff-leaved aster thrives in dry soils and tolerates drought. Its needle-like foliage turns yellow, orange, and purple in fall, shortly after the purple flowers appear. This aster reaches 15 to 20 inches tall and typically grows in acidic soils. Try it as an edging plant in front of sweet goldenrod.
Part Sun or Shady Sites
Blue wood aster (Symphyotrichum cordifolius) grows two to three feet high and bears heart-shaped leaves that turn burgundy in fall. Its blue (or violet) and yellow flowers appear in early to mid-fall, and its seeds attract goldfinches and chickadees. Blue wood aster tolerates sun or partial shade and moist or dry soils, and goes well with wreath goldenrod. Deer may browse it lightly.
White wood aster (Eurybia divaricata) This woodland beauty may be on your property already, or along local roadsides. It thrives in dry shade and produces white, fragrant flowers in late summer, along with dark-green, shiny foliage. White wood aster grows 18 inches to two feet high. Plant it under existing shade trees or at the base of large shrubs. It will be attractive with wreath or zigzag goldenrod and blue wood aster.
Smooth aster (Symphyotrichum laeve)
With upright growth habit and arching stems, smooth aster grows 18 inches to three feet high. Violet and yellow flowers appear from late summer through fall. It takes full sun to part shade in moist or dry soils. This aster is appropriate for the perennial border. It can also be combined with wreath or zigzag goldenrod in a shade garden or woodland setting.
Calico aster (Symphyotrichum lateriflorum)
Calico aster grows one to four feet high with a shrubby habit. Its late-summer flowers are starry, pinkish daisies with rosy centers. Calico aster prefers part shade and moist soils. Try it with wreath goldenrod and the lavender-hued mistflower (Conoclinium coelestinum) in a pollinator garden receiving dappled sunlight.
Since we can only present a few of the many native asters and goldenrods, do try to familiarize yourself with more of these valuable plants. (And add some to your garden!)
But don’t forget the wild places you might explore on your own, perhaps with a field guide or two in hand. Many Connecticut Audubon Society sanctuaries feature meadows and are terrific places to witness the vital relationships between these plants that bloom so late in the season and the many birds and other creatures that need them.
Mark Richardson and Dan Jaffe, Native Plants for New England Gardens, Globe Pequot, 2018
Natural Gardening for Birds by Julie Zickfoose and the editors and writers of Bird Watcher’s Digest, Rodale Press, 2001
Many other sources were helpful for this article, including the Missouri Botanic Garden Plant Finder:
The North Carolina Extension Garden Toolbox: