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Aster
Symphyotrichum
Aster blooms from September through October.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Aster
Plant it in full sun. It prefers moderate water. It is hardy in USDA zones 3–8. Expect it to reach about 3 ft tall and 2 ft wide at maturity, in roughly 2 years (a house reading).
No toxicity note is on file for Aster. That is not a clearance: check its safety for people and pets before planting.
What was checked
Mature height and spread, hardiness zones, sun, water, bloom months and color and the trait tags were checked against named botanical sources for this plant, with what the sources could not settle written down; years to mature size rests on a recorded house rule where no publisher states one, and is marked so; its common name and alternate names have not been checked yet. Each fact above carries its own mark. The planting, spacing and size sections are derived from these checked facts by a fixed rule, not checked separately, and the plant type is the library's own classification.
When to plant Aster
Plant Aster in early spring as soon as the soil is workable, or in early fall at least six weeks before your first frost, so roots establish in cool weather. In zone 5, the middle of its hardy zones 3 to 8, spring means April to June and fall means August or September. Once settled, it blooms from September to October.
Month-by-month timing for your zone is on the planting calendar; if you garden near zone 5, the middle of this plant's hardy range, start with zone 5 in April. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.
How big does Aster get?
3 fttall5 ft 7 inan adult2 ftwideSee Aster in a garden plan: the planner shows it in 3D beside everything else you add, growing toward this size over the years.
How far apart to plant Aster
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Aster about 2 ft apart, center to center, so each plant has room to reach its full width.
Add Aster to a garden plan and the planner draws it at its full width, so you see the spacing before you buy.
Where these facts come from
Aster's height, spread, hardiness zones, sun, water, bloom months and color, trait tags, soil, diseases, pests and toxicity were checked against 18 published sources on August 24, 2026. Each one is linked below with every fact it carried, which can include a fact this page still marks as not yet checked, because a source carrying a value is not the same as the value being held to the standard. Facts not in that list, and the planting, spacing and size sections, are not covered by these sources.
- NC State Extensiongenus Symphyotrichumheight, spread, sun, water, bloom months and color, trait tags, soil, diseases and pests
- Missouri Botanical GardenSymphyotrichum novi-belgiiheight, spread, hardiness zones, sun, water, bloom months and color, trait tags and diseases
- Missouri Botanical GardenSymphyotrichum oblongifoliumheight, spread, hardiness zones, sun, water, bloom months and color, trait tags and soil
- NC State ExtensionSymphyotrichum novae-angliaeheight, spread, hardiness zones, sun, bloom months and color, trait tags and pests
- Missouri Botanical GardenPlant Finderhardiness zones, sun, water, bloom months and color, soil and diseases
- University of Illinois ExtensionSymphyotrichum lateriflorumheight, hardiness zones, sun, water, bloom months and color and pests
- University of Wisconsin Horticulturegenus, Aster Symphyotrichum spp.height, sun, water, bloom months and color, soil and diseases
- Chicago Botanic GardenSymphyotrichum pilosumheight, spread, hardiness zones, sun and trait tags
- Missouri Botanical GardenSymphyotrichum novae-angliaeheight, spread, hardiness zones, sun and trait tags
- Missouri Botanical GardenSymphyotrichum laeveheight, spread, hardiness zones, sun and trait tags
- Missouri Botanical GardenSymphyotrichum ericoidesheight, spread, hardiness zones, sun and trait tags
- NC State ExtensionSymphyotrichum oblongifoliumheight, spread, hardiness zones, sun and trait tags
- Penn State ExtensionSymphyotrichum novae-angliae, New England asterheight, hardiness zones, sun and trait tags
- Penn State ExtensionSymphyotrichum laeve, smooth asterheight, hardiness zones, sun and trait tags
- Prairie Moon NurserySymphyotrichum novae-angliaeheight, hardiness zones, sun and trait tags
- Lady Bird Johnson Wildflower CenterSymphyotrichum novae-angliaeheight, sun and trait tags
- Penn State Extensiontoxicity
- uvm.eduUniversity of Vermont Extension System, Department of Plant and Soil S...toxicity
How the checking works, and what each standard covers, is on the verified plants page.
Comes in 12 varieties across 5 colors
Same genus, similar care - pick the color you are growing.
- Alma Pötschke
- Aromatic
- Kickin' Carmine Red
- October Skies
- Patricia Ballard
- Professor Kippenberg
- Purple Dome
- Raydon's Favorite
- Snow Flurry
- Wood's Blue
- Wood's Pink
- Wood's Purple
Compare every variety in the Aster group
Every figure is the variety's own page fact. Tap a name to open it.
| Variety | Color | Blooms | Hardiness | Sun | Size (H × W) |
|---|---|---|---|---|---|
| Alma Pötschke | Pink | Sep–Oct | Zones 4–8 | Full sun | 3 ft × 2 ft |
| Aromatic | Purple | Sep–Nov | Zones 3–8 | Full sun | 24 in × 24 in |
| Asterthis page | Purple | Sep–Oct | Zones 3–8 | Full sun | 3 ft × 2 ft |
| Kickin' Carmine Red | Red | Aug–Oct | Zones 4–8 | Full sun | 20 in × 20 in |
| October Skies | Blue | Sep–Oct | Zones 3–8 | Full sun | 1.5 ft × 2.5 ft |
| Patricia Ballard | Pink | Sep–Oct | Zones 4–8 | Full sun | 3 ft × 2 ft |
| Professor Kippenberg | Blue | Aug–Oct | Zones 4–8 | Full sun | 16 in × 16 in |
| Purple Dome | Purple | Sep–Oct | Zones 3–8 | Full sun | 24 in × 24 in |
| Raydon's Favorite | Blue | Sep–Nov | Zones 3–8 | Full sun | 2.5 ft × 3 ft |
| Snow Flurry | White | Sep–Oct | Zones 3–8 | Full sun | 8 in × 24 in |
| Wood's Blue | Blue | Sep–Oct | Zones 4–8 | Full sun | 16 in × 16 in |
| Wood's Pink | Pink | Aug–Oct | Zones 4–8 | Full sun | 16 in × 16 in |
| Wood's Purple | Purple | Aug–Oct | Zones 4–8 | Full sun | 16 in × 16 in |
Good to know about Aster
Curated from university extensions, botanic gardens and other primary sources, with the source named on every note. A note reports what its source says; where that differs from a fact above, the fact above is this entry's stored value, and its mark says whether it has been checked.
Worth knowing
Asters bloom into fall when almost nothing else does, making them a keystone nectar source for migrating monarchs and bumble bees fattening up before winter. per Penn State and Xerces
Cut back or leave standing
Some sources say cut plants to the ground after flowering; others say leave the stalks and seed heads for winter birds and insects, then cut down in late winter. per NC State and Wisconsin
The Chelsea chop
Pinch the stems back by up to half in late spring to early summer for shorter, bushier, less-floppy plants with more flowers. Stop by about mid-July so buds form. per Illinois and Nebraska
Powdery mildew
The common aster problem, worst in shade and crowding. Give it full sun, wide spacing and good airflow, thin dense clumps, and choose mildew-resistant cultivars. per Wisconsin and NC State
New England vs New York
New England aster is taller and coarser with hairy leaves; New York aster (the Michaelmas daisy) is shorter with smooth leaves and a bit more mildew-prone. per NC State
Feeds caterpillars and birds
Asters host Pearl Crescent caterpillars and other butterfly larvae; after bloom the seed heads feed finches, chickadees, juncos and other songbirds. per NC State
What pairs well with Aster
Good companions share its growing conditions and add something it lacks: an earlier or later bloom, a lower carpet in front, or structure through winter.
Honeysuckle
Shares full sun and moderate water; blooms in late spring, before this one opens; both are strong pollinator plants, and they feed in different months; climbs to 13 ft behind it, height without the footprint.
Hollyhock
Shares full sun and moderate water; blooms in early summer, before this one opens; both are strong pollinator plants, and they feed in different months; taller at 6 ft, for the layer behind it.
Spiderwort
Takes full sun to part sun and moderate water; blooms in early summer, before this one opens; both offer pollinator forage, in different months; both are North American natives.
Ninebark
Shares full sun and moderate water; blooms in late spring, before this one opens; both are strong pollinator plants, and they feed in different months; taller at 6.5 ft, for the layer behind it.
Chives
Shares full sun and moderate water; blooms in late spring, before this one opens; both are strong pollinator plants, and they feed in different months; both are North American natives.
Japanese Stewartia
Takes full sun to part sun and moderate water; blooms in early summer, before this one opens; both are strong pollinator plants, and they feed in different months; taller at 16 ft, for the layer behind it.
Delphinium
Shares full sun and moderate water; blooms in early summer, before this one opens; both are strong pollinator plants, and they feed in different months; taller at 4.5 ft, for the layer behind it.
California Poppy
Shares full sun and low to moderate water; blooms in late spring, before this one opens; both are strong pollinator plants, and they feed in different months; both are North American natives.
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