Buttonbush
Cephalanthus occidentalis
Madder family (Rubiaceae)

Description: This native woody shrub is usually 3-8' tall, but sometimes reaches 20' and achieves the stature of a small tree. It branches frequently and has a bushy appearance. The lower branches become woody and brown, while new growth is green or red. The leaves are usually opposite, although sometimes they occur in whorls of 3. They are up to 6" long and 2" across, ovate or ovate-oblong in shape, and have slender petioles, smooth margins, and a glossy upper surface. In the typical variety of this species (described here), both the young branches and leaves are hairless, although there exists a less common variety of Buttonbush with pubescent branches and leaves.

From 1-3 spherical flowerheads occur on a flowering stalk that branches when more than a single flowerhead occurs. Some of the upper branches may terminate with these flowerheads, or a flowering stalk may occur from the axils of the leaves. Each mature flowerhead is about 1–1" across, and is covered all around with small white or cream flowers. Each flower has a narrow corolla about 1/3" long, with 4 small spreading lobes at its apex. There are 4 short stamens and a single white style that is quite long and undivided, projecting beyond the corolla. This latter characteristic provides the flowerhead with a starburst appearance. The small green calyx is tubular with 4 small teeth. It is about " in length. The blooming period occurs during the summer (usually mid-summer) and lasts about 1 month. The flowers are sweetly fragrant. Each flower is replaced by a fruit that is obpyramidal (like a narrow upside-down pyramid). It contains 2 cells, each containing a single seed (occasionally, one of the cells is empty). The root system consists of a woody taproot.

Cultivation: The preference is full or partial sun, wet to moist conditions, and a fertile soil with high organic content. This shrub is semi-aquatic, and can withstand flooded conditions for long periods of time. It will also grow in soil that is consistently moist, rather than wet, but will be smaller in size.

Range & Habitat: Buttonbush occurs in most areas of Illinois, except for a few counties in the NW (see Distribution Map). It is occasional to locally common. Habitats include openings in floodplain forests, wet thickets, shrubby swamps, wet depressions in black soil prairies, marshes, bogs, seeps, and borders of rivers and small lakes. This shrub can form extensive colonies at some locations.

Faunal Associations: The nectar of the flowers attracts long-tongued bees, butterflies, and skippers primarily. Less typical insect visitors of the flowers include short-tongued bees, wasps, flies, and beetles. Some of the insects in this latter group are attracted to the pollen. The foliage is eaten by the caterpillars of Darapsa versicolor (Hydrangea Sphinx). The seeds are occasionally eaten by ducks, geese, and rails, particularly Mallard Ducks. The branches, twigs, or foliage are eaten occasionally by the White-Tailed Deer and beavers. However, livestock that consume the foliage can be poisoned. Apparently, the seeds of Buttonbush are more extensively used by waterfowl in the southern Mississippi valley than in Illinois.

Photographic Location: A degraded moist prairie at Judge Webber Park in Urbana, Illinois. This area is prone to occasional flooding after heavy rains.

Comments: Buttonbush has attractive foliage and flowers. It is occasionally planted as an ornamental shrub. Because of the unique flowers, it is easy to identify in the field.

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