University of Vermont
Department of Plant and Soil Science
PERENNIAL PLANT FEATURE: FALL ASTERS
Dr. Leonard Perry, Horticulture Professor
University of Vermont
There are many reasons to use fall-blooming asters in landscapes.
There is much variety in this large group of hardy perennials, coming in
various heights and showy flower colors. You’ll find selections in all
shades of red, pink, purple, white, and even blue. They’re easy to
grow, most are native, and they’re one of the main plants for bees,
butterflies and other pollinators in the fall. They combine well with
ornamental grasses, rudbeckia, and coneflowers.
With so many to choose from, how does one begin? In addition to
favorite colors, look for ones that best fit your growing conditions,
desired habits, and that have disease resistance.
The starburst appearance of the flowers leads to the name “aster”, from the
Greek word for star. Asters give their name to the large composite
family— Asteraceae— that of sunflowers, dahlias, daisies, zinnias, and
similar flowers. The asters all used to be grouped together into one
“genus” (Aster), but thanks to recent botanical research they’ve been
regrouped with names more suited to botanists than gardeners. So for
instance, although the New England aster genus is now changed (Symphyotrichum),
the species name has remained the same (novae-angliae).
Generally, most asters prefer moist, well-drained soil and full sun.
There is a range of species, however, that can be grouped by their native
environments and corresponding garden preferences. The first group
prefers rich, moist soil in full sun. These include the species native
to meadows, prairies and marshes such as the New York (S. novi-belgii),
New England (S. novae-angliae), and flat-topped (D. umbellata)
asters. They prefer steady moisture. Ones that prefer moist
soil, but can tolerate dry sites, include the sky-blue (S. oolentangiense),
heath (S. ericoides), calico (S. lateriflorum), aromatic (S.
oblongifolium), and silky (S. sericeum) asters. Tatarian
aster (A. tataricus) in this group, a Siberian native, is quite
adaptable to various soils.
The second group of asters also prefer full sun, along with cool nights, and
very well-drained soil. This is because they are native to seashores
and mountains where soil drainage is excellent. They may be
short-lived over only a few years, particularly if conditions aren’t just
right. In this group you’ll find the European Michaelmas daisy native
to Asia Minor (A. amellus)—a name often given to many asters as they
bloom around this Christian holiday of September 29. Others in this
group are the Frikart’s (A. xfrikartii) aster, of garden origin, and
East Indies (A. tongolensis) aster native to western China and India.
The third group of native aster species tolerate shade (under 4 hours direct
sun per day), but bloom better in part shade (4 to 8 hours of direct
sun). The blue wood aster (S. cordifolium), Drummond’s aster (S.
drummondii), white wood aster (E. divaricata), and big leaf
aster (A. macrophyllus) are in this group. Although they prefer
moist soils rich in organic matter (humus), they will tolerate some drought.
In perennial trials at the Chicago Botanic Gardens, 119 asters were
evaluated over six years. They were rated based on flowering, health,
habit, and hardiness. In this USDA zone 5 site (-10 to -20 degrees F
average winter minimum), seven asters stood out with five-star
ratings. These top asters included ‘Jin Dai’ tatarian aster, white
wood aster and its cultivar (cultivated variety) ‘Eastern Star’, ‘Snow
Flurry’ heath aster, calico aster and its cultivar ‘Lady in Black’, and
‘Raydon’s Favorite’ aromatic aster. For a rock garden or low wall,
where cascading stems are desired, ‘Snow Flurry’ would be a good
choice. For perennial gardens and naturalistic landscape masses, good
choices would include asters with bushy habits—‘Jin Dai’, ‘Lady in Black’,
or ‘Raydon’s Favorite’.
In addition, there were 19 asters that rated good, with four stars. These
good asters included a couple of New England asters—the rosy pink
‘Harrington’s Pink’ and deep pink ‘Honeysong Pink’, and three New York
asters-- the light lavender ‘Blaubox’, lavender-blue ‘Climax’, and
purple-pink ‘Rosenwichtel’. Most selections you may find of the asters are
in the New York and New England species. Perhaps the reasons
that more didn’t rate more highly relate to habit and potential
problems. Aromatic asters tend to be less problem-prone, and good
New England asters can get to four to five feet tall and fall over under
some conditions, particularly low light. Cutting them back in early
summer by one third to one half will make them more bushy, with no need to
One of the more recent introductions of New England asters, and one of the
most popular asters, ‘Purple Dome’ came from the Mt. Cuba Center and gardens
in Delaware. It is violet-purple and low, only growing to about 16
inches high and about 2 feet wide. This makes it a good choice for
fronts of borders, along walks, massed, or even containers. It bloomed
over two months in Chicago, from early September to early November. ‘Vibrant
Dome’ is a bright pink sport of this compact cultivar, not in these trials
but popular and available.
‘Purple Dome’ is a good example of how resistance to diseases can vary by
site. Often considered to have excellent resistance to powdery mildew,
in the Chicago trials this cultivar was only rated as fair.
Asters may get rust or powdery mildew diseases on leaves. The former
was seen more on the New York asters in the Chicago trials, while the latter
disease was seen more on the New England asters. Giving good air
circulation around plants, and disposing of leaves in the fall (not in the
compost) will help lessen these. There are several sprays, organic and
synthetic, that can be used for these too.
A main destructive insect of asters may be the lacebug, a small grayish
insect that appears in midsummer and sucks the plant juices from the
undersides of leaves, primarily of the New York and related types.
Leaves turn yellowish and eventually brown and fall off. Organic or
synthetic insect sprays can be used for control. Read and follow all
label directions for best control, and safety for you and the environment.
Deer and rabbits can be quite fond of asters, too. There are repellent
sprays for these. Low fencing for rabbits, and deer netting for these
may be needed if repellents don’t work. Keys are to train these
animals early in the season, and to rotate among more than one repellent
strategy or spray.
Several asters have been bred as alternatives to fall garden mums, including
the lavender ‘Ariel’, violet ‘Celeste’, and the purple ‘Pixie Dark’.
Results from the Chicago trials show these only live a year or two, so
should be grown as annual flowers. Since the New York asters have
problems, and are short-lived, they are not recommended either, even though
Keeping asters healthy during the growing season—in part, growing them under
the right conditions-- will go a long way toward helping them survive the
subsequent winter. More on asters and their culture, as well as other
perennial evaluations, can be found in the reports from trials manager
Richard Hawke and his Chicago Botanic Garden trials website
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