7 Reasons Asters Are The #1 Fall Flower
Asters bring a burst of late-season color, pollinator benefits, and versatility, a few of the many reasons they deserve a spot in the garden. Celebrate this star performer with gardening expert Katherine Rowe and enjoy its buzzing vibrance in jewel tones of the season.
Contents
Asters are well-known “stars of the fall garden” with their flash of color among muted autumnal hues and fading warm-season blooms. Their starry ray flowers bring an infusion of blue, purple, pink, and white shades. They also benefit bees and other pollinators with rich late-season nectar.
Heights and colors vary among the species, as do growing conditions. This diversity makes the late-season bloomers versatile and well-adapted, with numerous North American native species to choose from.
Both in the wild and in the garden, fall asters bridge transitioning seasonal conditions with aesthetic and ecological value. Blooming from late summer through frost, they fit a variety of styles and situations with ease and reliable performance. Here are the main reasons why asters are the stars of the fall garden.
Native Species
Asters—many native to North America—are easy-going mainstays with daisy-ray flowers that put on a showy display well into fall.
There are over 250 species of asters worldwide, and if you’re looking for the native North American types, here’s a quick note on the genus. The reclassified genus name Symphyotrichum generally distinguishes native North American asters from Eurasian asters (Aster spp.). This isn’t a hard and fast rule, though. However, ”aster” is still the term we all relate to.
Other native asters go by equally long botanical names and include Doellingeria and Eurybia. It helps to know this when narrowing down native species for your growing area.
Popular Natives
There are about 100 native U.S. species. A few highlights include:
- New England (S. novae-angliae) – Native to grasslands and woodland edges, New England asters are hardy and adaptable, found in old homesteads and along fencerows growing with abandon. The upright growers bloom in purple clusters on three to six-foot stems. Hardy in zones 4-8.
- Smooth (S. laeve) – More compact at two to four feet tall with sky-blue flowers and good mildew resistance. Zones 4-8.
- Aromatic (S. oblongifolium) – Violet-blue flowers emerge in September through November on dense, one to two-foot forms. Crushed leaves are fragrant, and this one does well in sandy or clay soils. Zones 3-8.
- New York (S. novi-belgii) – New York tolerates more moisture than other types. On bushy stems, blooms range from white to blue-purple to lavender. Zones 4-8.
- Bushy (S. dumosum) – Bushy is more petite at one to three feet tall, with good mildew and rust resistance. Pink, blue, and purple ray flowers cover foliage that remains attractive all season. Zones 4-8.
- Skyblue (S. oolentangiense) – Skyblue is a dwarf grower that reaches two feet high and tolerates a wide range of soils as long as they’re well-draining. Zones 3-8.
- Heath (A. ericoides) – Heaths are multi-branched and compact. The one-to-three-foot shrubby plants produce a profusion of small white rays from August through October. They tolerate drought and eroded sites, including clay, shallow, and rocky soils. Heath also makes a pretty cut flower. Zones 3-10.
An Aster For Every Growing Situation
Symphyotrichum grows across climates, soil types, and sun exposures, making them versatile and easy to use in the landscape. Some species tolerate dry, rocky sites, while others do fine with wet feet in rich soils. They span full sun to shady exposures, and with exceptional cold hardiness, they perennialize in USDA zones 3-9.
Here are a few examples of cultural variations:
- S. oolentangiense, or skyblue aster, is drought-tolerant and well-suited to dry or shallow soils.
- S. laevis, or smooth blue aster, tolerates various site conditions.
- S. cordifolius, blue wood aster, naturalizes along woodland edges and does well in dry areas.
Pollinator Benefits
Each flower holds fine, colorful ray petals that fan around a contrasting central yellow disc, holding pollen and nectar. The late-season bloom provides food for native bees and other beneficial insects. It also supports late migratory butterflies like monarchs as they travel to warmer climes.
Within the genus, choose those with varying bloom times. Successional flowering ensures a food source late into cool weather. Especially late bloomers like aromatic aster (Symphyotrichum oblongifolium) last well into fall with sought-after forage.
The National Wildlife Federation has a native plant finder tool to help locate species specific to your growing area. This specificity ensures selections are adapted to the area’s temperatures, soils, weather, plant communities, and wildlife partnerships. This tool also extends to pollinators that utilize the plant, from their larvae to butterflies, bees, and moths. Smooth asters, for example, host the caterpillar of the pearl crescent butterfly, who overwinter at its base.
A North Dakota State University study evaluates pollinator preferences among select native perennials and their cultivars. Asters rated high on attracting hoverflies and bees (especially New England aster and a cultivar of aromatic aster, ‘October Skies’). Hoverflies are a beneficial insect, helpful in controlling aphid populations.
In the study, New England (S. novae-angliae) was the biggest draw for pollinators, followed by S. oblongifolium ‘October Skies,’ and smooth aster (S. laeve). Each cultivar also drew pollinators at varying levels.
In the winter, as the perennials enter dormancy, leave them standing instead of cutting them back. Their stems host hollow-stem nesting bees.
Seeds for Songbirds
The floriferous perennials yield seeds for winter forage post-bloom. Birds not only eat insects drawn to the flowers but forage on seeds in the fall and winter as other resources become lean. The seeds are food sources for goldfinches, chickadees, nuthatches, towhees, and more.
Wild turkeys and ruffed grouse also enjoy the seeds. Mammals like squirrels, chipmunks, and deer use them for forage.
Ornamental Value
A perennial that blends high color in the low season with ecological benefits is a win for the display. The showiness of these ornamentals is a prime reason to incorporate them. They shine in drifts or dotted throughout the bed. They’re a fit for the perennial border, butterfly, woodland, naturalized, rockery, and cottage garden. Use them in mass plantings, meadows, and ecological restoration areas.
In pots, they make excellent accents and filler specimens. Increasingly, asters are becoming substitutes for the omnipresent mum, with richer pollen and nectar offerings and seasons of recurrent color. They also make beautiful cut flowers.
Pair asters with other fall flowering perennials like rudbeckia, echinacea, solidago, and sedum. It’s gorgeous with ornamental grasses for contrast in foliage and form. Hydrangea, drying in vintage tones on the stem, makes a lovely backdrop.
Predictable and Reliable
In the right growing conditions, asters are relatively easy to grow, with durable performance and reliable fall flowering. The autumnal hallmarks burst into color as the day length shortens and temperatures cool.
The low-maintenance perennials don’t require deadheading unless you want to limit reseeding. The vigorous growers spread through seeds and rhizomes. Deadheading and pulling unwanted volunteers helps keep them in bounds if necessary.
Tall varieties may get leggy and flop over without support. These benefit from sheering or cutting back halfway in late spring for a new flush of growth before flowering. They may drop lower leaves as the season progresses; disguise this by interplanting with other perennials.
Vigorous selections benefit from dividing every few years to reinvigorate growth. The crown becomes crowded and declines over time.
Asters generally have few growing problems, but they are susceptible to powdery mildew and rust diseases, particularly in the fall. Ensure plenty of air circulation and thin stems in summer if crowding inhibits airflow. Thinning, along with good soil drainage, helps prevent foliar diseases.
Standout Performers
In addition to the straight species are their cultivars with a strong performance in terms of improved form and flowering and disease-resistance. Chicago Botanic and Mt. Cuba Center conducted trials on many North American natives and associated cultivars, with four and five-star selections rising to the top. Since these trials, numerous new varieties are ready to become the season’s grand finale.
S. laeve ‘Bluebird’
This smooth variety yields abundant violet-blue flowers, large compared to many others and with good coverage. In loose clusters, they emerge from September through late October.
Smooth, leathery, blue-green leaves line three to four feet stems. With a vigorous, upright habit, they benefit from pinching to retain form (but usually don’t need staking). ‘Bluebird’ is drought-tolerant.
S. oblongifolium ‘October Skies’
‘October Skies’ is an aromatic variety with a violet cloud of flowers from September to October. Two-foot stems maintain a shrubby form.
They grow vigorously with branches that support themselves in a coarse, mounding habit. ‘October Skies’ draws a number of beneficial insects and is pest and disease-resistant.
S. novi-belgii ‘Wood’s Purple’
This New York aster is a routine top performer in the fall, displaying medium blue-purple flowers on dwarf, dense plants. Flowers give good coverage and rich color to the 14-inch mounding forms.
Despite robust growth, ‘Wood’s Purple’ retains its form without pinching.
S. lateriflorum ‘Lady in Black’
‘Lady in Black’ is a calico aster with green-purple leaves throughout the growing season. Its small white flowers stand out amongst the dark foliage.
The yellow central floret disks transition to pinkish-purple as they age. The upright, vase-shaped variety shows good resistance to powdery mildew.
S. ericoides ‘Snow Flurry’
‘Snow Flurry’ is a heath aster that forms an attractive mounding ground cover. The low form reaches only eight inches high but spreads four feet wide.
A blanket of petite white flowers obscures foliage in September and October. Use ‘Snow Flurry’ as a carpet at the bed edge or to spill over walls and pots. These are disease-resistant and tolerate dry conditions.
Aster novae-angliae ‘Pink Crush’
‘Pink Crush’ is a New England variety that brings a less wild look with well-formed branching and blooms. Rose pink ray petals are darker toward the center around gold florets.
The crowded aster blossoms are large, and cover the dark green leaves in early to mid-fall. Stems reach up to two feet tall with a well-rounded habit.
