Illustration
Summersweet
Clethra alnifolia
Also called sweet pepperbush
Summersweet blooms from July through August.
Months here are Northern Hemisphere months; in the Southern Hemisphere, shift them by six months.
Growing Summersweet
Plant it in part shade. It prefers high water. It is hardy in USDA zones 3–9. Expect it to reach about 6 ft tall and 5 ft wide at maturity, in roughly 4 years (not yet checked).
No toxicity note is on file for Summersweet. That is not a clearance: check its safety for people and pets before planting.
What was checked
Mature height and spread, 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, and each fact above says which. 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 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. In zone 6, the middle of its hardy zones 3 to 9, 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; if you garden near zone 6, the middle of this plant's hardy range, start with zone 6 in March. Derived from the plant's category, zones and bloom months plus typical zone frost dates, not checked separately.
How big does Summersweet get?
6 fttall5 ft 7 inan adult5 ftwideSee Summersweet 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 Summersweet
Derived from the mature spread above by a fixed rule, not checked separately: spacing is the spread, center to center.
Space Summersweet about 5 ft apart, center to center, so each plant has room to reach its full width.
Add Summersweet 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
Summersweet's height, spread, hardiness zones, sun and trait tags were checked against 10 published sources on July 30, 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.
- Fine GardeningSweet pepperbush, Clethra alnifoliaheight, spread, hardiness zones, sun, years to mature size and trait tags
- NC State ExtensionClethra alnifoliaheight, spread, hardiness zones, sun, years to mature size and trait tags
- Missouri Botanical GardenClethra alnifoliaheight, spread, hardiness zones, sun and trait tags
- The Morton ArboretumSummersweet clethraheight, hardiness zones, sun, years to mature size and trait tags
- Clemson Home and Garden Information CenterSummersweet Clethraheight, spread, sun and trait tags
- piedmontmastergardeners.orgPiedmont Master Gardeners, Virginia Cooperative Extension (Clethra aln...height, sun, years to mature size and trait tags
- University of Illinois ExtensionSummersweet Clethraheight, spread, sun and trait tags
- Lady Bird Johnson Wildflower CenterClethra alnifoliaheight, sun and trait tags
- en.wikipedia.orgWikipedia (Clethra alnifolia)height and trait tags
- Portland NurseryClethrasun
How the checking works, and what each standard covers, is on the verified plants page.
Comes in 6 varieties across 2 colors
Same plant, same care - pick the color you are growing.
Compare every variety in the Summersweet group
Every figure is the variety's own page fact. Tap a name to open it.
| Variety | Color | Blooms | Hardiness | Sun | Size (H × W) |
|---|---|---|---|---|---|
| Hummingbird | White | Jul–Aug | Zones 3–9 | Part shade | 3 ft × 4 ft |
| Pink Spire | Pink | Jul–Aug | Zones 3–9 | Part shade | 6 ft × 5 ft |
| Ruby Spice | Pink | Jul–Aug | Zones 3–9 | Part shade | 6 ft × 5 ft |
| Sixteen Candles | White | Jul–Aug | Zones 3–9 | Part shade | 4 ft × 4 ft |
| Sugartina Crystalina | White | Jul–Aug | Zones 3–9 | Part shade | 2.5 ft × 3 ft |
| Summersweetthis page | White | Jul–Aug | Zones 3–9 | Part shade | 6 ft × 5 ft |
| Vanilla Spice | White | Jul–Aug | Zones 3–9 | Part shade | 5 ft × 4 ft |
Good to know about Summersweet
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
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.
Rhododendron
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; evergreen, so the bed keeps its shape 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.
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.
Hellebore
Shares part shade and moderate to high water; blooms in late winter, before this one opens; both offer pollinator forage, in different months; evergreen, so the bed keeps its shape through winter.
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.
Flowering Dogwood
Shares 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.
Windflower
Takes part sun to part shade and moderate to high water; blooms in early 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.
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.
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