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Aster
Symphyotrichum
Aster blooms from September through October.
Mature size, hardiness zones, sun and the trait tags were checked against named botanical sources for this plant. The bloom months and water need on this page were not.
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.
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. For the middle of its hardy zones 3 to 8 range, 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: for the middle of its range, start with zone 5 in April.
Comes in 11 varieties across 5 colors
Same plant, same care - pick the color you are growing.
Good to know about Aster
Curated from university extensions, botanic gardens and other primary sources, with the source named on every note.
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.
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 native plants.
Butterfly Weed
Shares full sun and low to moderate water; blooms in early summer, before this one opens; both are strong pollinator plants, and they feed in different months; both are native plants.
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 native plants.
Mullein
Shares full sun and low to moderate water; blooms in early summer, before this one opens; both are strong pollinator plants, and they feed in different months; taller at 3.9 ft, for the layer behind it.
Dill
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; yellow against purple, for contrast.
Passionflower
Shares full sun and moderate water; opens in midsummer and overlaps into this one's season; both are strong pollinator plants; climbs to 13 ft behind it, height without the footprint.
Lobelia
Takes full sun to part sun and moderate water; opens in late spring and overlaps into this one's season; both are strong pollinator plants; lower at 8 in, for the front of the border.
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Drop this plant onto a 3D plan, see how it fills in, and watch your whole garden bloom across the year.