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Design

Awesome Asters

The best ones have strong habits and disease resistance, and they end the season with a bang

Fine Gardening - Issue 165

What would autumn be like without asters? Boring, that’s what. Thankfully, I live in a place with a plethora of native asters that dot and decorate roadsides, fields, woodlands, and wild spaces. Their ubiquitous nature sometimes saddles them with the reputation of looking too wild, and while you might get your fix of asters from these borrowed landscapes, I wouldn’t want to be without their cheery flowers in my garden, as well. Asters mark the changing seasons in a pageant of colors, blending beautifully with an assortment of grasses and other late-showing perennials.

Aster (the Greek word for “star”) is so-named for the starburst effect of its daisylike flowers, but I like to think that its stellar floral show has something to do with it, too. The botanical name of this autumnal star has changed from the simplicity of Aster to tongue twisters such as Doellengeria, Eurybia, and Symphyotrichum—confounding gardeners and professionals alike. Complicating matters a bit, the new names have not been universally embraced; the Royal Horticultural Society, for one, has not yet adopted the changes, but many botanical gardens, native-plant societies, and nurseries have already made the switch. Possibly more important than knowing the Latin name of a given plant is knowing if it is, in fact, a “star” or one of the many asters that, instead, become a disease-infested mess by midseason.


At a Glance: ‘Jindai’ Tatarian aster (photo above)

USDA Hardiness Zones: 4 to 8

Conditions: Full sun to partial shade; moderately fertile, moist, well-drained soil

Season: Flowers appear from late summer through fall.

Propagation: Divide in spring, every two to three years.

Pests: Verticillium wilt, gray mold, powdery mildew, rusts, white smut, aster yellows, and many fungal leaf spots and stem cankers. Also prone to rosy blister gall, aphids, mites, slugs, snails, and nematodes.

 


Without flowers, ‘Jindai’ Tatarian aster (Aster tataricus ‘Jindai’) might be difficult to peg as an aster. Coarse basal leaves, nearly 2 feet long, look like those of horse­radish or tobacco. Flowering stems begin to grow in midsummer, eventually reaching up to 4 feet tall—that’s a good 2 to 3 feet shorter than the species. Come autumn, its lineage is no longer in doubt: Clusters of pretty violet-blue-and-yellow flowers bloom well into late fall and sometimes even early winter. The species has a reputation for spreading widely, and even though ‘Jindai’ makes a sizable patch in a few years, I have not found it to be a thug. Bold-textured ‘Jindai’ pairs well with small-leaved asters or any ornamental grass, be it short or tall.

 

Top performers that are worth a second look

One of the heartbreaks of our trial was the lack of success in overwintering any cultivars of Frikart’s daisy (Aster × frikartii); they all balked at our wet winter soils. Luckily, we found that Wartburgstern’ East Indies aster (Aster tongolensis ‘Wartburgstern’) is a hardy substitute. Vibrant, violet-blue flowers with bright orange centers hover 20 inches above the low mat of dark green leaves, which remain attractive all summer. Although ‘Wartburgstern’ (or ‘Wartburg Star’, as it is often called) is described as blooming all summer, we saw flowers for only about a month from early to midsummer. Sure, the shorter bloom period was disappointing, but that only made the flowers all the more precious.

The low mounding habit of ‘Snow Flurry’ white heath aster (Symphyotrichum ericoides ‘Snow Flurry’) sets it apart from other asters. Its arching stems seem to undulate across the ground, reaching nearly 4 feet wide but only 8 inches tall. ‘Snow Flurry’ makes a superb ground cover or edging plant, but it is utter perfection cascading over the edge of a wall or a container. No description of the diminutive flowers can do justice to the actual show: A veritable snowstorm of white flowers blanket the stems in autumn. The tiny linear leaves are more reminiscent of heaths (Erica spp. and cvs., Zones 5–11) than of asters. ‘Snow Flurry’ is also tolerant of dry conditions.

‘Raydon’s Favorite’ aromatic aster (Symphyotrichum oblongifolium ‘Raydon’s Favorite’) was fairly uncommon when we planted it but quickly became a perennial favorite in our trial. The plant is loaded with blue-purple flowers that keep appearing for a long time; in fact, the plant is so eager to get going that precocious blossoms pop up for several weeks before blooming begins in earnest in midsummer. A billowy habit gives ‘Raydon’s Favorite’ an informal look that suits it to mass plantings and naturalizing. Aromatic asters are better alternatives to New England asters (Symphyotrichum novae-angliae) because they are more resistant to powdery mildew. I think aromatic aster will play an important role in future plant breeding for disease-resistant cultivars and hybrids.

‘Eastern Star’ white wood aster (Eurybia divaricata ‘Eastern Star’) is one of the few asters that grows well in shady gardens, although some morning sun enhances its floral display. From midsummer on, smallish white flowers with yellow centers are borne aplenty on wiry, dark burgundy stems over dark green leaves. You can expect an upright mounded habit, similar to the species, but the cultivar ‘Eastern Star’ features larger flowers and darker green leaves. Its arching stems were a bit more recumbent, too, especially when weighed down with flowers. White wood aster is particularly fetching in large drifts in high-shade landscapes.

It was a friend who told me that ‘Kylie’ aster (Symphyotrichum ‘Kylie’), a hybrid of New England aster and heath aster, was a must-have for my trial. ‘Kylie’ seems to have gotten the best of both parents, with narrow, dark green leaves—free of rust and mildew—and a robust clumping habit. To be honest, the healthy foliage was quickly forgotten by autumn, when ‘Kylie’ turned into a soft pink cloud with scores of small semidouble flowers crowding the tops of the erect stems. Every year, ‘Kylie’ got both the butterfly vote and mine, proving that sometimes it pays to take a friend’s advice.

My first impression ofDoktor Otto Petschek’ Italian aster (Aster amellus ‘Doktor Otto Petschek’) as just another lavender-flowered aster was way off—as was the notion that it was named after a Bond villain. Flowers by the hundreds cloaked this compact clumper for weeks every fall, looking stunning and remaining healthy when many other asters were shabby or floppy. ‘Doktor Otto Petschek’ delivered year after year and is clearly a great disease-resistant alternative to New England and New York asters (Symphyotrichum novi-belgii). Italian asters, in general, like a lot of sun and need good drainage to stay healthy; cool nighttime temperatures are also preferred.

‘Lady in Black’ calico aster (Symphyotrichum lateriflorum ‘Lady in Black’) has a graceful profile with thin, wiry stems that arch out and over the large bushy plant. Sprays of white blossoms, just shy of half an inch across, cover the upper side of the horizontal branches in late summer. It’s hard not to get excited when the new leaves emerge bronze and then, amazingly, remain a strong purple all summer (full sun is essential to get the best color). Calico aster gets its name because the yellow disks at the center of the flowers change to purplish pink as they age—a pleasing color echo with the purple leaves of ‘Lady in Black’. While calico asters were untroubled by mildew, rabbits were harder to keep at bay.


Basics

Asters, in a nutshell

There are roughly 250 species of asters that are native to North America, Europe, and Asia. Although fairly ubiquitous, they are not without their challenges.

Division keeps plants healthy

Fast growers, such as New England aster, New York aster, calico aster, and flat-topped aster (Doellingeria umbellata), benefit from crown division every few years in early spring or autumn to reinvigorate the plants and keep them shapely. If left alone, the plants will die out in the centers.

A new enemy is on the loose

Chrysanthemum lace bug (Corythucha marmorata), which became a problem in our trial in just the past few years, sucks nutrients from aster leaves, turning them sickly and off-colored. Severely infested plants drop most of their leaves and sometimes don’t recover. Only chemical controls, unfortunately, seem to be effective in combatting these pests.

Shade isn’t necessarily an issue

Asters generally grow best in moist, well-drained soils with plenty of sunlight. Woodland asters, such as blue wood aster (Symphyotrichum cordifolium), Drummond’s aster (S. drummondii), white wood aster (Eurybia divaricata), and bigleaf aster (E. macrophylla), tolerate deep shade but will produce the best flower displays with some morning sun.

Stake ’em or shear ’em

Tall asters might need staking, especially in shady or windy sites, but can be sheared to half their height in early to late spring to keep them shorter. Deadheading, while not required, will reduce unwanted seedlings.

Want disease-free plants? Stay away from New England and New York

Powdery mildew and rust are potentially devastating diseases on some asters—marring leaves and sapping plant energy. Affected plants might drop their leaves, have reduced flower production, and just look shabby. Cultivars of New England aster were more troubled by powdery mildew in our trial, whereas cultivars and hybrids of New York aster were rarely rust-free.


Up-and-Comers to Check Out

‘Arrested Development’ aster (Aster ‘Arrested Development’) is a new introduction noted for its short size. I’ve enjoyed its deep lavender-blue flowers whenever I can catch it in bloom—I have to be one step ahead of the rabbits, though. It touts an early-fall bloom date, a fact that we observed for the past two years, when as if on cue, the flowers opened on September 18. It is ironic that rabbits kept nibbling at the tips, thus arresting its development even further. Our plants topped out at 9 inches tall and 15 inches wide due to repeated browsing, but ‘Arrested Development’ should reach a bushy 12 to 15 inches tall and wide—without competition, of course.

Given our affinity for ‘Raydon’s Favorite’, we naturally had high expectations for Raydon’s Birthday Pink’ aromatic aster (Symphyotrichum oblongifolium ‘Raydon’s Birthday Pink’), and it did not disappoint. The first precocious flowers showed up in late summer, as if they just couldn’t wait for the party to begin. An exceptional display of light pink flowers, 1½ inches across, could be counted on from early to midfall. ‘Raydon’s Birthday Pink’ formed robust bushy mounds up to 32 inches tall and a whopping 84 inches wide, outpacing ‘Raydon’s Favorite’ by 30 inches. Mildew was no issue, but plants were minimally infested with lace bugs.

‘Bridal Veil’ aster (Symphyotrichum ‘Bridal Veil’) has its origin at the Chicago Botanic Garden; it was selected from a cross between ‘Snow Flurry’ and an unknown aster. ‘Bridal Veil’ has upward-arching stems that ultimately turn pendulous, developing a graceful weeping habit as the season progresses. Living up to its name, the fine-textured, cascading stems are thick with ½-inch-diameter white flowers from early fall on. At 40 inches tall and 68 inches wide, ‘Bridal Veil’ takes up some space, but its organic habit is worth it. Add mildew resistance as well as drought and salt tolerance to the mix and ‘Bridal Veil’ is perfect for both urban and naturalistic gardens.

We all know that fall is the time of asters, but ‘Napsbury’ East Indies aster (Aster tongolensis ‘Napsbury’) didn’t get the memo. Pretty lavender-and-orange flowers, 2½ inches across, rise above rosettes of dark green leaves for a month, starting in early summer. East Indies asters like relatively fertile, moist soils with good drainage, and will soak up all the sun you give them but won’t mind a bit of shade, too. At 14 inches tall and 20 inches wide, place ‘Napsbury’ right at the front of the border to enjoy its fleeting summer show to the fullest.


Aster Trial Results

Trial Parameters

How many: Since 2003, the Chicago Botanic Garden has evaluated 145 different asters in our comparative trials.

How long: A minimum of six years

Zone: 5b

Conditions: Full sun to full shade; alkaline, clay-loam, well-drained soil

Care: Minimal, allowing plants to thrive or fail under natural conditions

Observations: Ornamental traits; growth and adaptation to environmental and soil conditions; disease or pest problems; plant injury or winter losses

Rating Name Height Width Flower color Flower size (dia.) Flower production Mildew resistance Rust resistance
★ ★ ★ Aster amellus ‘Doktor Otto Petschek’ 20 in. 36 in. Lavender 1¼ in. Heavy Excellent Excellent
Aster frikartii ‘Mönch’ 22 in. 32 in. Lavender-blue 2 in. Moderate Excellent Poor
Aster frikartii ‘Wunder von Stäfa’ 23 in. 32 in. Lavender-blue 2 in. Low Excellent Fair
★ ★ ★ ★ Aster tataricus ‘Jindai’ 40 in. 32 in. Violet-blue 1 in. Heavy Excellent Excellent
★ ★ ★ Aster tongolensis ‘Wartburgstern’ 20 in. 24 in. Violet-blue 2 in. Moderate Excellent Good
★ ★ ★ Doellingeria umbellata 60 in. 55 in. White ½ in. Heavy Excellent Excellent
★ ★ ★ ★ Eurybia divaricata 24 in. 46 in. White ¾ in. Heavy Excellent Excellent
★ ★ ★ ★ Eurybia divaricata ‘Eastern Star’ 21 in. 36 in. White 1¼ in. Heavy Excellent Excellent
★ ★ Eurybia macrophylla 49 in. 36 in. Light purple 1½ in. Heavy Excellent Very poor
★ ★ Symphyotrichum ‘Bill’s Big Blue’ 58 in. 52 in. Lavender-blue 1 in. Low Good Excellent
★ ★ ★ Symphyotrichum ‘Cape Cod’ 49 in. 62 in. White 58 in. Heavy Excellent Excellent
★ ★ Symphyotrichum ‘Cassie’ 36 in. 30 in. Light purple 1¼ in. Moderate Fair Excellent
Symphyotrichum ‘Celeste’ 35 in. 28 in. Violet 1 in. Low Excellent Very poor
Symphyotrichum ‘Coombe Fishacre’ 34 in. 34 in. Pink ¾ in. Low Very poor Excellent
★ ★ ★ Symphyotrichum ‘Kylie’ 46 in. 40 in. Pale pink ¾ in. Heavy Excellent Excellent
Symphyotrichum ‘Lilac Blue Admiral’ 39 in. 34 in. Lavender ¾ in. Low Good Very poor
Symphyotrichum ‘Melody’ 27 in. 24 in. Lavender 1½ in. Moderate Very poor Very poor
★ ★ Symphyotrichum ‘Milka’ 36 in. 28 in. Light violet  1 in. Moderate Good Fair
★ ★ Symphyotrichum ‘Miss Bessie’ 59 in. 40 in. Lavender 1 in. N/A Good Good
★ ★ Symphyotrichum ‘Ochtendgloren’ 40 in. 40 in. Purple-pink ¾ in. Moderate Excellent Very poor
Symphyotrichum ‘Red Star’ 15 in. 21 in. Magenta 1½ in. Low Very poor Poor
★ ★ Symphyotrichum ‘White Climax’ 50 in. 36 in. White 1¼ in. Moderate Poor Excellent
★ ★ Symphyotrichum cordifolium ‘Ideal’ 60 in. 35 in. Lavender ¾ in. Heavy Excellent Poor
★ ★ ★ Symphyotrichum drummondii var. drummondii 49 in. 45 in. Lavender-blue ¾ in. Moderate Good Excellent
Symphyotrichum ericoides ‘Blue Star’ 33 in. 50 in. Pale blue ½ in. Heavy Excellent Very poor
★ ★ ★ Symphyotrichum ericoides ‘Erlkönig’ 42 in. 56 in. Pale lavender-blue ½ in. Heavy Good Good
★ ★ ★ Symphyotrichum ericoides ‘First Snow’ 19 in. 40 in. White ½ in. Heavy Excellent Fair
★ ★ ★ ★ Symphyotrichum ericoides ‘Snow Flurry’ 8 in. 48 in. White 38 in. Heavy Excellent Excellent
Symphyotrichum laeve ‘Bluebird’ 49 in. 36 in. Violet-blue 1 in. Low Excellent Good
Symphyotrichum laeve ‘Calliope’ 57 in. 60 in. Lilac-purple 138 in. Moderate Excellent Very poor
★ ★ ★ ★ Symphyotrichum lateriflorum 39 in. 60 in. White 38 in. Heavy Excellent Excellent
★ ★ ★ ★ Symphyotrichum lateriflorum ‘Lady in Black’ 34 in. 50 in. White ½ in. Heavy Excellent Excellent
★ ★ ★ Symphyotrichum lateriflorum ‘Lovely’ 25 in. 26 in. Pale purple 38 in. Moderate Excellent Excellent
★ ★ Symphyotrichum novae-angliae ‘Andenken an Alma Pötschke’ 38 in. 60 in. Cerise-pink  1½ in. Heavy Fair Excellent
★ ★ Symphyotrichum novae-angliae ‘Andenken an Paul Gerbe’ 52 in. 49 in. Purple-pink 1½ in. Moderate Fair Excellent
★ ★ Symphyotrichum novae-angliae ‘Barr’s Blue’ 55 in. 68 in. Purple-blue  1½ in. Heavy Poor Excellent
★ ★ ★ Symphyotrichum novae-angliae ‘Harrington’s Pink’ 60 in. 50 in. Rosy pink 1¼ in. Heavy Fair Excellent
Symphyotrichum novae-angliae ‘Hella Lacy’ 34 in. 48 in. Light violet-blue 1 in. Low Very poor Excellent
★ ★ ★ Symphyotrichum novae-angliae ‘Honeysong Pink’ 59 in. 40 in. Deep pink 1½ in. Heavy Fair Excellent
★ ★ Symphyotrichum novae-angliae ‘Mrs. S. T. Wright’ 49 in. 53 in. Purple  2¼ in. Moderate Poor Excellent
★ ★ Symphyotrichum novae-angliae ‘Purple Dome’ 16 in. 24 in. Violet-purple 1½ in. Heavy Fair Excellent
★ ★ Symphyotrichum novae-angliae ‘Treasure’ 64 in. 38 in. Purple 2 in. Heavy Poor Excellent
★ ★ Symphyotrichum novae-angliae ‘Wedding Lace’ 64 in. 54 in. White 1¾ in. Heavy Poor Excellent
Symphyotrichum novi-belgii ‘Alice Haslem’ 12 in. 20 in. Light red 1½ in. Heavy Very poor Excellent
★ ★ Symphyotrichum novi-belgii ‘Blaubox’ 28 in. 32 in. Light lavender 1½ in. Heavy Very poor Good
Symphyotrichum novi-belgii ‘Blue Lagoon’ 19 in. 28 in. Violet-blue 1 in. Heavy Excellent Very poor
★ ★ Symphyotrichum novi-belgii ‘Blue Lake’ 55 in. 50 in. Violet-blue 1 in. Low Excellent Very poor
Symphyotrichum novi-belgii ‘Boningale White’ 21 in. 21 in. White 2 in. Low Very poor Excellent
Symphyotrichum novi-belgii ‘Butterfly Blue’ 32 in. 22 in. Lavender ¾ in. Low Very poor Good
★ ★ Symphyotrichum novi-belgii ‘Choristers’ 64 in. 75 in. White ½ in. Heavy Excellent Poor
★ ★ ★ Symphyotrichum novi-belgii ‘Climax’ 46 in. 40 in. Lavender-blue 1¼ in. Heavy Excellent Excellent
Symphyotrichum novi-belgii ‘Daniela’ 12 in. 24 in. Purple 1¼ in. Low Excellent Very poor
Symphyotrichum novi-belgii ‘Freda Ballard’ 20 in. 18 in. Purple-red 1¼ in. Low Poor Excellent
Symphyotrichum novi-belgii ‘Harrison’s Blue’ 36 in. 38 in. Violet-blue 1½ in. Heavy Poor Very poor
Symphyotrichum novi-belgii ‘Jenny’ 14 in. 17 in. Purple-red 1½ in. Low Excellent Very poor
Symphyotrichum novi-belgii ‘Kiesapphire Sapphire’ 24 in. 22 in. Vivid violet 1½ in. Low Excellent Very poor
★ ★ Symphyotrichum novi-belgii ‘Lady in Blue’ 14 in. 30 in. Lavender-blue 1¼ in. Low Excellent Very poor
Symphyotrichum novi-belgii ‘Marie Ballard’ 32 in. 20 in. Lavender-blue 1¾ in. Low Poor Fair
★ ★ Symphyotrichum novi-belgii ‘Mariore’ 18 in. 30 in. Pink 1¼ in. Heavy Very poor Very poor
★ ★ Symphyotrichum novi-belgii ‘Porzellan’ 62 in. 60 in. Light purple 1½ in. Heavy Good Very poor
Symphyotrichum novi-belgii ‘Professor Anton Kippenberg’ 11 in. 26 in. Lavender-blue 1 in. Low Excellent Very poor
★ ★ ★ Symphyotrichum novi-belgii ‘Rosenwichtel’ 12 in. 30 in. Purple-pink 1¼ in. Heavy Excellent Excellent
★ ★ Symphyotrichum novi-belgii ‘Schneekissen’ (‘Snow Cushion’) 10 in. 16 in. White 1 in. Moderate Excellent Good
★ ★ Symphyotrichum novi-belgii ‘Violet Carpet’ 9 in. 36 in. Violet-blue 1 in. Low Excellent Good
Symphyotrichum novi-belgii ‘White Swan’ 36 in. 28 in. White 1½ in. Moderate Very poor Excellent
★ ★ Symphyotrichum novi-belgii ‘Wood’s Blue’ 11 in. 30 in. Lavender-blue 1½ in. Low Good Excellent
★ ★ Symphyotrichum novi-belgii ‘Wood’s Light Blue’ 8 in. 24 in. Light blue 1 in. Heavy Excellent Excellent
★ ★ Symphyotrichum novi-belgii ‘Wood’s Purple’ 9 in. 18 in. Purple 1¼ in. Moderate Excellent Excellent
★ ★ ★ Symphyotrichum oblongifolium 36 in. 40 in. Lavender-blue 1½ in. Moderate Excellent Excellent
★ ★ ★ Symphyotrichum oblongifolium ‘Fanny’s Aster’ 47 in. 40 in. Light purple 1¼ in. Moderate Good Excellent
★ ★ ★ Symphyotrichum oblongifolium ‘October Skies’ 35 in. 50 in. Lavender-blue 1¼ in. Moderate Fair Excellent
★ ★ ★ ★ Symphyotrichum oblongifolium ‘Raydon’s Favorite’ 38 in. 53 in. Blue-purple 1¼ in. Heavy Excellent Excellent
★ ★ ★ Symphyotrichum oblongifolium var. angustatus 35 in. 65 in. Lavender-blue 1¼ in. Moderate Excellent Excellent
★ ★ Symphyotrichum oolentangiense 45 in. 28 in. Lavender 1 in. Low Fair Excellent
★ ★ Symphyotrichum sericeum 22 in. 32 in. Purple-blue 1½ in. Low Excellent Excellent
★ ★ ★ Symphyotrichum turbinellum 58 in. 56 in. Violet-blue 1¼ in. Heavy Good Excellent

Rating key

★★★★ Excellent

★★★ Good

★★ Fair

Poor

 

 

Richard Hawke is the plant-evaluation manager at the Chicago Botanic Garden in Glencoe, Illinois.

SOURCES

The following mail-order plant sellers offer many of the asters featured:

Far Reaches Farm, Port Townsend, Wash.; 360-385-5114; farreachesfarm.com

Joy Creek Nursery, Scappoose, Ore.; 503-543-7474; joycreek.com

Lazy S’S Farm Nursery, 2360 Spotswood Trail, Barboursville, VA 22923; lazyssfarm.com

Stokes Seeds, Buffalo, N.Y.; 800-396-9238; stokeseeds.com

For the complete chart of results from the aster trial, go to FineGardening.com/extras.

Photos, except where noted: Danielle Sherry; pp. 30–31 and p. 32 (bottom left), Nancy J. Ondra; p. 32 (top left) and p. 34 (bottom), courtesy of Forestfarm; p. 32 (right), Jennifer Benner

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