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Ironweed
Vernonia
Also called ironwood
Ironweed blooms from August through September.
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 Ironweed
Plant it in full sun. It prefers moderate water. It is hardy in USDA zones 4–9. Expect it to reach about 4.9 ft tall and 2 ft wide at maturity, in roughly 2 years.
When to plant Ironweed
Plant Ironweed 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 4 to 9 range, spring means March to May and fall means August or September. Once settled, it blooms from August to September.
Month-by-month timing for your zone is on the planting calendar: for the middle of its range, start with zone 6 in March.
Good to know about Ironweed
Curated from university extensions, botanic gardens and other primary sources, with the source named on every note.
Worth knowing
In the daisy family, yet its flower heads have only tiny disc florets and no petal-like ray florets, so they read as fluffy tufts, not daisies. per NC State
Watering splits by species
The wet-meadow types (New York, western/prairie ironweed) want steady moisture and suit rain gardens; upland Appalachian and Letterman's ironweed prefer average to dry soil. Match yours to the site. per NC State
Deer resistant, one exception
Bitter foliage makes New York, giant and Letterman's ironweed reliably deer resistant. The exception is Appalachian ironweed (V. glauca), which deer are drawn to: avoid it in deer country. per NC State
Size varies by species
The slug covers several Vernonia species: from compact Letterman's ironweed at 2 to 3.5 ft up to New York (5 to 8 ft) and giant ironweed near 12 ft. per NC State
Cut tall types back
The tall types lean and flop. A late-spring Chelsea chop, cutting them back by a third to a half before flower buds set, keeps them shorter and upright. per NC State
Late-season pollinator magnet
It blooms in late summer and fall when little else flowers, feeding butterflies, monarchs, bees and other pollinators through the pre-winter and migration window. Songbirds later eat the seeds. per NC State
Leave winter stems standing
The hollow dead stems shelter stem-nesting bees, so leave them standing about 12 to 24 in over winter before cutting down, rather than a hard fall cleanup. per NC State
What pairs well with Ironweed
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.
Thyme
Shares full sun and low to moderate water; blooms in late spring, before this one opens; low at 6 in, to carpet the ground beneath; both are strong pollinator plants, and they feed in different months.
Creeping Phlox
Shares full sun and low to moderate water; blooms in mid spring, before this one opens; low at 6 in, to carpet the ground beneath; both are strong pollinator plants, and they feed in different months.
Sweet Alyssum
Shares full sun and moderate water; overlaps, then carries the display into mid fall; low at 5 in, to carpet the ground beneath; both are strong pollinator plants.
English Daisy
Shares full sun and moderate water; blooms in mid spring, before this one opens; low at 6 in, to carpet the ground beneath; both offer pollinator forage, in different months.
Tulip Tree
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 native plants.
Lobelia
Takes full sun to part sun and moderate water; low at 8 in, to carpet the ground beneath; opens in late spring and overlaps into this one's season; both are strong pollinator plants.
Pansy
Takes full sun to part sun and moderate water; blooms in early spring, before this one opens; low at 8 in, to carpet the ground beneath; both offer pollinator forage, in different months.
Hyacinth
Shares full sun and moderate water; blooms in early spring, before this one opens; lower at 10 in, for the front of the border; both offer pollinator forage, in different months.
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