A few weeks ago my husband and I were taking our usual morning walk alongside Lake Butte des Morts. While his gaze turns upward toward waterfowl and songbirds, my eyes are drawn to the sides of the trail and the plants that grow there. This particular morning I was stopped in my tracks by the most unusual shrub I have ever seen.
It was a couple feet tall and featured perfectly round, fragrant, ping pong ball-sized flowers with what looked like pins sticking out of them. My thoughts tumbled quickly. “Wow! What the heck is that?” “How have I not seen this before?” “I sure hope this isn’t a new invasive plant!”
The eye-catcher turned out to be a native perennial shrub called buttonbush, Latin name Cephalanthus occidentalis.. Other names are button ball, honey-bells, button willow and riverbush.
Buttonbush thrives in moist, neutral or slightly acidic soils and is a perfect addition to a rain garden, pond or stream edge, bog or marshy area. They prefer part shade to full sun. New stems are reddish while older ones have smooth, gray-green bark. Older stems may be twisted, crooked, or leaning, and the crown is irregularly shaped, so if you are looking for a perfectly symmetrical ornamental shrub, this one isn’t for you. It isn’t messy or sloppy in appearance, just casually asymmetrical. Light pruning can be done in spring if a branch or two is bothersome.
Leaves are a glossy, dark green similar to dogwood leaves, and the unusual button flowers appear late July to early August. Buttonbushes can grow 6-12 feet tall and spread 4-8 feet wide. After flowering, the “pins” which are actually the flower pistils, fall off, leaving green balls the size of gumballs. These later turn red and then into brown nutlets that persist through winter.
To keep buttonbush smaller, it can be cut back to six inches in winter or early spring. The next summer it will grow to three feet or so. Even uncut, it may die back to the ground in winter but will re-grow again the next year.
Buttonbush flowers provide nectar for at least thirteen species of butterflies, as well as moths, hummingbirds, bees and other insects. Twenty-four species of birds, including ducks, other shorebirds and water birds eat the seeds and three species of mammals eat the twigs. Wood ducks like to use the plant for protection of brooding nests. Leaves host the larvae of several butterflies. It is a good plant for erosion control along shorelines. It can form dense stands and the plants have a swollen base that stabilizes the bank.
Buttonbush is commercially available, but can easily be grown by sowing fresh seed gathered in late summer or early fall after the seeds have turned brown. Unrooted cuttings can be pushed into moist soil where they will establish on their own.
One caution: Buttonbush foliage is poisonous to humans and other mammals, causing vomiting, convulsions and paralysis if ingested.