Summersweet
Clethra alnifolia
Also called sweet pepperbush
Summersweet blooms from July through August.
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 Summersweet
Plant it in part shade. It prefers high water. It is hardy in USDA zones 3–9. Expect it to reach about 5.9 ft tall and 4.9 ft wide at maturity, in roughly 4 years.
When to plant Summersweet
Plant Summersweet 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 9 range, spring means March to May and fall means August or September. Once settled, it blooms from July to August.
Month-by-month timing for your zone is on the planting calendar: for the middle of its range, start with zone 6 in March.
Comes in 6 varieties across 2 colors
Same plant, same care - pick the color you are growing.
Good to know about Summersweet
Curated from university extensions, botanic gardens and other primary sources, with the source named on every note.
Worth knowing
A rare fragrant shrub that blooms well even in full shade, and it flowers in mid to late summer when most other shrubs have finished. per Clemson
Mature size varies widely
Sources split on size. The wild species in wet ground can top 3 m, but ordinary garden plants and compact cultivars run 1.2 to 2.4 m or less. per NC State and Morton Arboretum
Zone 3 is marginal
NC State rates it to zone 3, but Illinois, Wisconsin, and Morton call zone 4 the reliable cold limit. In zone 3, expect winter risk and a sheltered spot. per NC State and Wisconsin
A shrub for wet spots
Genuinely flood-tolerant once established: a top pick for rain gardens, pond and stream edges, and low spots that flood, and it holds streambanks against erosion. per University of Maryland
Suckers into colonies
It spreads by suckers into wide thickets, which is perfect for naturalizing but means yearly sucker removal if you want one tidy, single-stemmed shrub. per NC State
A pollinator magnet
High-quality nectar and pollen draw bees, butterflies, and hummingbirds during a nectar-scarce stretch of summer. Songbirds eat the seed, and it hosts the sweet pepperbush moth. per NC State
Mites mean it's too dry
Few serious pests, but spider mites flare when it bakes on a hot, dry site. The fix is water and moist siting, not spraying. per NC State
What pairs well with Summersweet
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.
Bugleweed
Shares part shade and moderate to high water; blooms in mid spring, before this one opens; low at 6 in, to carpet the ground beneath; evergreen, so the bed keeps its shape through winter.
Jacob's Ladder
Shares part shade and moderate to high water; blooms in late spring, before this one opens; both are strong pollinator plants, and they feed in different months; lower at 1.6 ft, for the front of the border.
Pansy
Takes part sun to part shade and moderate to high 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.
Globeflower
Takes part sun to part shade and high water; blooms in late spring, before this one opens; both offer pollinator forage, in different months; lower at 2 ft, for the front of the border.
Lobelia
Takes part sun to part shade and moderate to high water; low at 8 in, to carpet the ground beneath; overlaps, then carries the display into early fall; both are strong pollinator plants.
Eastern Redbud
Takes part sun to part shade and moderate to high water; blooms in mid spring, before this one opens; both are strong pollinator plants, and they feed in different months; taller at 23 ft, for the layer behind it.
Serviceberry
Takes part sun to part shade and moderate to high water; blooms in mid spring, before this one opens; both are strong pollinator plants, and they feed in different months; taller at 20 ft, for the layer behind it.
Impatiens
Takes part shade to full shade and high water; overlaps, then carries the display into mid fall; both offer pollinator forage; lower at 12 in, for the front of the border.
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