Buttonbush
Cephalanthus occidentalis · Rubiaceae
Perfectly round, white, pincushion flowers like small satellites, sweetly scented, in midsummer. A native shrub of pond edges that will grow in standing water.
- Size
- 6½ ft tall, 6½ ft wide
- Zones
- 5 to 9
- Light
- Full sun to part sun
- Flowers
- Late June to early August
- Pets
- Toxic (moderate)
- Job in a bed
- Anchor
A bed built around buttonbush
The planner designed this bed around buttonbush when this page was made: a 16 × 8 ft (4.9 × 2.4 m) English border in zone 6, full sun. It chose the other plants from the 251 that suit those conditions and its wet soil, and says below why buttonbush stands where it does.
The plants
- 1 Buttonbush × 1, white
- 2 Lingonberry × 8, pink
- 3 Mouse-ear coreopsis 'Nana' × 27, yellow
- 4 Siberian iris 'Caesar's Brother' × 3, purple
- 5 White mugwort × 4, cream
- 6 Palm sedge × 5, green leaves
- 7 Golden ragwort × 14, yellow
- 8 Camassia × 4, blue
- 9 Checkered lily × 12, purple
Why this plant
- The only globes. The others are bells, daisies, plumes and others. Shape reads at a distance, where colours blur.
- The only white. White sits between stronger colours and calms them.
- Part of the bed's structure. Shrubs and grasses keep their shape when the perennials die down. So do lingonberry and palm sedge.
Why here
- Anchors a back corner. At 6½ ft it is the tallest plant here, and the tallest close the ends of the bed, where they stand in front of nothing.
- A step in the back row. Next to white mugwort (5 ft): no two neighbours there are the same height, so the back steps up and down like a skyline.
- One plant, alone. A shrub is seen as an object, and needs clear ground around it.
Why now
- In flower for six weeks. From late June to early August.
- Fills a gap. For six of those weeks nothing else on the plan is in flower.
Planned as an English border: 10 of the 12 groups (83%) are drifts, longer along the bed than they are deep. Early colour comes from bulbs planted between the other plants: camassia and checkered lily. The flowering is at its height in late May, with 5 kinds out together.
The planner's own design check: 12 Excellent, 4 Good, 1 Satisfactory. It flags one thing to watch: Nothing on this plan is highly poisonous or an aggressive spreader.
Open this bed in the planner Change its size, the sun or the style, move plants about, or swap one for another.
Where buttonbush goes in a border
At 6½ ft it belongs at the back of a bed. In the planner's ten height classes it is very tall (5 to 6½ ft).
Its job: anchor. A shrub that gives the bed permanent structure. Planted singly, as soon as the front edge is laid; everything else is arranged around it.
The round flowers are unlike anything else and are loved by butterflies. It needs wet soil to look its best. Cut it back hard if it becomes leggy.
- Pond edges and rain gardens
- Butterflies and bees
- Wet soil where little else grows
What to plant with buttonbush
Plants recorded as good partners for it, and what each pairing does:
- Swamp milkweed: in flower together for five weeks, from early July; low enough (4 ft) to stand in front of it.
- Cardinal flower: in flower together for two weeks, from late July; spires rising out of its mound; low enough (3½ ft) to stand in front of it.
- Blue flag iris: flowers first, late May to late June, so the spot is never empty; low enough (2½ ft) to stand in front of it; happy in the same wet soil.
Questions about buttonbush
Does buttonbush need sun or shade?
Buttonbush grows in full sun (6 or more hours of direct sun a day) and part sun (4 to 6 hours of sun, including some afternoon sun).
It wants moist to wet soil, rich in organic matter, and plenty of water. It copes with soil that stays wet.
What zones does buttonbush grow in?
USDA zones 5 to 9. It is hardy to zone 5, which means it survives winter nights down to about −10 °F (−23 °C).
Gardening in Canada? Use the USDA zone for your town: Canada's own zone map uses different numbers.
When does buttonbush flower in my zone?
In zone 5 it flowers late June to early August. As a summer flower it moves about half a week for every zone: earlier where it is warmer.
| Zone 5 | Late June to early August |
|---|---|
| Zone 6 | Late June to early August |
| Zone 7 | Late June to late July |
| Zone 8 | Late June to late July |
| Zone 9 | Mid June to mid July |
Worked out from Hopkins' bioclimatic law: spring arrives about four days later for each degree of latitude north, and one zone is roughly two degrees. A warm spring or a cold one moves any garden two weeks either way.
How far apart should buttonbush be planted?
5 ft (150 cm) apart, from the middle of one plant to the middle of the next. That is a little closer than its full width of 6½ ft (200 cm), so a group knits into one patch.
It grows 6½ ft (200 cm) tall. Give it the full distance from anything taller, or it will lean out towards the light.
How many buttonbush plants do I need?
Usually one. At 5 ft (150 cm) across, it is a plant you place, not one you mass. For a hedge or screen, set them 5 ft apart: three plants for a 10 ft run.
In the bed above, the planner used one in one group.
Is buttonbush poisonous to dogs and cats?
Yes: moderate toxicity to people, dogs, cats and horses. The leaves and bark are poisonous if eaten in quantity, especially to grazing animals.
Rated from NC State Extension. Where references disagree, the more cautious rating is used.
Is there a pet-safe plant like buttonbush?
These come closest to doing what buttonbush does, and no toxicity is recorded for them:
- Witherod viburnum 'Winterthur': the same job in a bed, the same size and the same colour; flowers early June to late June, wants moist soil.
- Highbush blueberry: the same job in a bed, the same size and the same colour; flowers early May to late May, wants moist soil.
- Summersweet: the same job in a bed, the same flowering time and the same colour; 12 in narrower, wants moist soil.
Matched the way the planner's Swap button matches plants: the same job in a bed, then size, then flowering time.
Do deer eat buttonbush?
Mostly not. NC State lists it as resistant to deer. No plant is proof against a hungry deer in a hard winter, but this one is low on the menu.
What flowers after buttonbush?
Buttonbush is over by early August. These start as it finishes and carry the same spot on, so it never goes flat:
- Cardinal flower: from late July to mid September, 3½ ft tall, to stand in front of it and cover its fading stems (a recorded partner).
- Hardy hibiscus: from late July to mid September, 5 ft tall, to stand in front of it and cover its fading stems.
- Tiger lily: from late July to late August, 4 ft tall, to stand in front of it and cover its fading stems.
What does buttonbush look like in winter?
Buttonbush drops its leaves and stands as bare branches. That is when to see its shape, and to prune it if it needs pruning.
Is buttonbush good for bees and butterflies?
Buttonbush is visited by pollinators, bees, butterflies, hummingbirds and songbirds.
It is native to the United States and Canada.
In these guides
- Plants for wet soil and rain gardens
- Plants for slopes and banks
- Garden plants toxic to cats
- Garden plants toxic to dogs
- Garden plants native to Canada
- Plants for hummingbirds
- Plants for butterflies
- Plants for bees
- Plants that feed garden birds
- Plants for a white garden
Every fact on record
- Type
- Shrub
- Size
- 6½ ft (200 cm) tall, 6½ ft (200 cm) wide
- Plant
- 5 ft (150 cm) apart
- Height class
- Very tall (5 to 6½ ft)
- Place in the bed
- Back
- Flowers
- Late June to early August; globes; white
- Leaves
- Medium texture, deciduous; green
- Shape
- Rounded, clumping
- Hardy in
- USDA zones 5 to 9
- Light
- Full sun, part sun
- Soil
- Rich, moist to wet
- Water
- High
- Feeding
- None needed
- Family
- Rubiaceae
- Comes from
- East Canada, U.S.A to Central America, Cuba
- Attracts
- Pollinators, bees, butterflies, hummingbirds, songbirds
- Stands up to
- Deer, heat, wet soil, erosion
Checked against NC State Extension. Flowering times are for zone 5: later in colder zones, earlier in warmer ones. Toxicity and spread information is a general gardening guide, not veterinary or medical advice, and invasive status varies by region. If a person or pet eats a plant, contact poison control or a vet. Check your local invasive species list before planting anything with a spread warning.