Cephalanthus spp.

buttonbush

Rubiaceae

North America, Central America, and Asia

Attracts Pollinators Attracts Butterflies Attracts Hummingbirds Fragrant (moderate)

Native to North America

SunFull Sun – Part Shade

WaterHigh

HardinessZones 5–9

Overview

Cephalanthus spp. is a genus of about six deciduous shrubs and small trees in the madder family (Rubiaceae), known as buttonbush and grown for their ball-shaped flowers. The species most often grown, Cephalanthus occidentalis, forms a rounded, multi-stemmed shrub 6-12 feet (1.8-3.6 m) tall and 4-8 feet (1.2-2.4 m) wide, with glossy, deep green leaves in pairs or whorls along the stems. In summer the branch tips carry spherical white flower heads about 1-1.5 inches (2.5-4 cm) across, each a pincushion of tiny tubular flowers tipped with protruding styles, fragrant and rich in nectar. Bees, butterflies, and hummingbirds work the flowers, which ripen into hard ball-like seed clusters that persist into winter and feed waterfowl. The genus grows naturally in wet ground, along pond and stream edges, in swamps, and in seasonally flooded soils, and tolerates standing water. Its need for constant moisture and its open, coarse habit in winter limit where it can be used, and the foliage is toxic to grazing livestock.

Native Range

Buttonbush species grow in North America, Central America, the Caribbean, and eastern Asia. Cephalanthus occidentalis is native across much of the eastern and southern United States into Mexico, where it grows in marshes, swamps, and the margins of ponds, lakes, and slow streams.

Suggested Uses

Buttonbush is grown in rain gardens, pond and stream edges, wet borders, and bioswales where its need for moisture is an asset. It is used in native and wildlife plantings for its nectar flowers and its seeds that feed ducks and other birds. The shrub also helps bind soil and filter runoff along banks and wet margins.

How to Identify

The round, white, pincushion flower heads, about the size of a large marble with tiny styles sticking out all around, are the clearest mark of the genus. Look for glossy, opposite or whorled leaves on a rounded wetland shrub, often standing in or near water. After bloom the flower balls harden into persistent brown seed heads that hang on through winter.

Appearance

Size & Dimensions

Height6' - 12'

Width/Spread4' - 8'

Reaches mature size in approximately 5 years

Colors

Flower Colors

white

Foliage Colors

green

Fall Foliage Colors

yellow

Bloom Information

Bloom Period

~6 weeks

Summer

Flowering comes in summer, generally June to August, with the white spherical heads opening over several weeks. The fragrant flowers draw heavy traffic from bees, butterflies, and hummingbirds. Each head matures into a hard, round cluster of nutlets that stays on the shrub into winter.

Detailed Descriptions

Foliage Description

glossy green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 6-10 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 7.5(Neutral)

357912

Soil Types

clay loam silt

Drainagewet

Water & Climate

Water Needs

High

Frost Tolerance

hardy

Time to Maturity

3-5 years

Care & Maintenance

Care Guide

Buttonbush grows in full sun to part shade on wet to moist soil, including clay, and tolerates standing water and seasonal flooding, across a pH of about 5.5 to 7.5. Constant moisture is the main need, as the shrub wilts and struggles in dry ground. The genus is hardy through cold winters and resprouts readily, even after being cut to the base. Growth is fast in rich, wet sites, and plants can become open and leggy without occasional hard pruning. Few pests trouble it, though the leaves are toxic to livestock that graze them. Plants are grown from seed, cuttings, or division for pond and rain-garden plantings.

Pruning

Buttonbush tolerates hard pruning and can be cut back close to the ground in late winter to renew its shape and hold it dense. Lighter pruning removes dead, weak, or crossing stems and shortens leggy growth. Cutting is done in late winter or early spring before new growth begins.