Buttonbush Cephalanthus occidentalis
Buttonbush (Cephalanthus occidentalis) is a deciduous perennial shrub in the Rubiaceae family, native to Swamps, pond edges and stream banks across eastern North America to Mexico. It grows 1.5–4 m (4.9–13 ft) tall and 1.5–3 m (4.9–10 ft) wide, wants full sun and high water, and is hardy to about -35 °C (-31 °F). Space plants about 2 m (6.6 ft) apart.
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Buttonbush at a glance
| Type | Perennial shrub, deciduous |
|---|---|
| Family | Rubiaceae |
| Mature height | 1.5–4 m (4.9–13 ft) |
| Mature spread | 1.5–3 m (4.9–10 ft) |
| Spacing | 2 m (6.6 ft) centre to centre |
| Sun | Full sun, at least 5 h of direct sun a day |
| Water | High; drought tolerance none, waterlogging tolerance high |
| Soil pH | 5–8 |
| Cold hardiness | About -35 °C (-31 °F) once established (roughly USDA zone 3) |
| Heat stress | Likely above about 38 °C (100 °F) |
| Flowering | from about June for 4–7 weeks (northern hemisphere; later in cold climates, earlier in warm ones) |
| Wind tolerance | Low |
| Pollinator value | High |
| Edible | Not grown as food |
| Native to | Swamps, pond edges and stream banks across eastern North America to Mexico |
| Common in gardens of | 🇺🇸 United States, 🇨🇦 Canada, 🇲🇽 Mexico |
Is Buttonbush toxic?
- People: moderately toxic
- Cats: moderately toxic
- Dogs: moderately toxic
- Parts: leaves, bark
Contains cephalanthin and other glycosides that have poisoned grazing animals; do not eat.
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 Buttonbush
No well-documented helpful pairing. Group it with plants that like full sun and high water.
Questions about Buttonbush
- How far apart should I plant Buttonbush?
- About 2 m (6.6 ft) apart, centre to centre. A mature plant spreads 1.5–3 m (4.9–10 ft).
- Does Buttonbush need full sun?
- Full sun: at least 5 hours of direct sun a day.
- How much water does Buttonbush need?
- High water. Drought tolerance is none and waterlogging tolerance high.
- How cold-hardy is Buttonbush?
- It tolerates about -35 °C (-31 °F) once established, roughly USDA zone 3.
- When does Buttonbush flower?
- From about June for 4–7 weeks (northern hemisphere; later in cold climates, earlier in warm ones).
- Is Buttonbush poisonous to cats and dogs?
- For cats it is moderately toxic; for dogs moderately toxic; for people moderately toxic. Contains cephalanthin and other glycosides that have poisoned grazing animals; do not eat.
- What grows well with Buttonbush?
- There is no well-documented companion pairing for Buttonbush. Group it with plants that like the same sun (full sun) 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
- Xerces Society pollinator conservation resources (regional plant lists and habitat guides), The Xerces Society for Invertebrate Conservation
Notes and assumptions
- Round, spiky balls of tiny white tubular flowers like pincushions in midsummer, crowded with butterflies and bees; the seed balls feed ducks. Grows standing in shallow water at the edge of ponds and rain gardens.
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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