Summersweet (sweet pepperbush) Clethra alnifolia
Summersweet (sweet pepperbush) (Clethra alnifolia) is a deciduous perennial shrub in the Clethraceae family, native to Coastal swamps and woods of eastern North America, from Maine to Florida and Texas. It grows 1–2.5 m (3.3–8.2 ft) tall and 1–2 m (3.3–6.6 ft) wide, wants part sun to part shade and high water, and is hardy to about -32 °C (-26 °F). Space plants about 1.2 m (3.9 ft) apart.
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Summersweet (sweet pepperbush) at a glance
| Type | Perennial shrub, deciduous |
|---|---|
| Family | Clethraceae |
| Mature height | 1–2.5 m (3.3–8.2 ft) |
| Mature spread | 1–2 m (3.3–6.6 ft) |
| Spacing | 1.2 m (3.9 ft) centre to centre |
| Sun | Part sun to part shade, at least 3 h of direct sun a day |
| Water | High; drought tolerance none, waterlogging tolerance high |
| Soil pH | 4.5–6.5 |
| Cold hardiness | About -32 °C (-26 °F) once established (roughly USDA zone 4) |
| Heat stress | Likely above about 34 °C (93 °F) |
| Flowering | from about July for 4–6 weeks (northern hemisphere; later in cold climates, earlier in warm ones) |
| Wind tolerance | Moderate |
| Pollinator value | High |
| Edible | Not grown as food |
| Native to | Coastal swamps and woods of eastern North America, from Maine to Florida and Texas |
| Common in gardens of | 🇺🇸 United States, 🇨🇦 Canada, 🇬🇧 United Kingdom, 🇩🇪 Germany, 🇳🇱 Netherlands |
Is Summersweet (sweet pepperbush) toxic?
- People: not known to be toxic
- Cats: not known to be toxic
- Dogs: not known to be toxic
Not known to be poisonous.
If a child or pet may have eaten part of a plant, call a poison centre or vet straight away.
Companion planting: what to grow with Summersweet (sweet pepperbush)
No well-documented helpful pairing. Group it with plants that like part sun to part shade and high water.
Questions about Summersweet (sweet pepperbush)
- How far apart should I plant Summersweet (sweet pepperbush)?
- About 1.2 m (3.9 ft) apart, centre to centre. A mature plant spreads 1–2 m (3.3–6.6 ft).
- Does Summersweet (sweet pepperbush) need full sun?
- Part sun to part shade: at least 3 hours of direct sun a day.
- How much water does Summersweet (sweet pepperbush) need?
- High water. Drought tolerance is none and waterlogging tolerance high.
- How cold-hardy is Summersweet (sweet pepperbush)?
- It tolerates about -32 °C (-26 °F) once established, roughly USDA zone 4.
- When does Summersweet (sweet pepperbush) flower?
- From about July for 4–6 weeks (northern hemisphere; later in cold climates, earlier in warm ones).
- Is Summersweet (sweet pepperbush) poisonous to cats and dogs?
- For cats it is not known to be toxic; for dogs not known to be toxic; for people not known to be toxic. Not known to be poisonous.
- What grows well with Summersweet (sweet pepperbush)?
- There is no well-documented companion pairing for Summersweet (sweet pepperbush). Group it with plants that like the same sun (part sun to part shade) and water (high).
Sources and evidence
Evidence grade A (A: strong evidence).
- Plants of the World Online (taxonomy, native range), Royal Botanic Gardens, Kew
- Missouri Botanical Garden Plant Finder, Missouri Botanical Garden
- RHS Find a Plant (plant profiles and growing guides), Royal Horticultural Society
Notes and assumptions
- Upright spikes of tiny, spicy-sweet scented white or pink flowers in high summer, when few shrubs flower, buzzing with bees and butterflies; yellow autumn colour. Takes salt spray, wet soil and shade.
Reference values for planning, not horticultural, veterinary or medical advice. Varieties, soils and local climates differ: check with a local nursery or extension service.
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