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Written By: Bianca Marcellino

Best known for its unique white, spikey flowers arranged in a dense ball, the Buttonbush (Cephalanthus occidentalis) is an ecologically significant, moisture-loving shrub spread across the Boreal Shield, Atlantic Maritime and Mixwood Plains.

Buttonbush is a fast-growing, hardy multi-stemmed shrub that grows between 2-4 meters in height and 2-4 meters in width. It is characterized by its striking small white flowers arranged into dense, spherical clusters with pistils extending ~1cm beyond the petals, thus serving as a popular ornamental shrub. Flowers typically bloom in late summer from June through to August, but with blooms only lasting 3-4 days.

Once blooming concludes, Buttonbush produces small reddish-brown seed balls composed of many nutlets resembling buttons that persist through the winter. Leaves are dark green and glossy with deep veins, oblong in shape and presented in pairs or threes. Buttonbush has a woody above-ground trunk that turns to a more tender herbaceous plant above, often with twisted stems.

Buttonbush Quick Facts:

Form: Shrub (deciduous)
Size: 1.8 – 3.7 meters (tall and wide)
Light Requirements: Partial shade to full sun
Moisture Requirements: Moist, wet
Soil: Clay, sand, loam
Habitat: Wetlands, waterbody margins and shallow standing water (riparian, swamp/marsh, bog/fen)
Canadian Distribution: Nova Scotia, New Brunswick, Quebec, Ontario

Buttonbush is well known for the strong fragrance of the white flower spheres. These flowers are ecologically important as their fragrance is highly attractive to a variety of different pollinators including bees, butterflies, and hummingbirds.

Once flowering ends, the fruiting body develops in Fall followed by the overwintering black nutlets (seed pods). The seed pods are also an important food source for birds including many waterfowl. Buttonbush is the host plant for the titan and hydrangea sphinx moth and therefore serves as an important food source across multiple food webs and at all stages of organismal life.

Due to its rapid growth rate, usually uncharacteristic of most native species, Buttonbush is often planted in riparian habitats (adjacent to/near wetlands) to aid in soil stabilization and prevent erosion.

It is important to note that Buttonbush leaves contain the glucoside cephalothin, which is toxic to people, pets and livestock when ingested and can induce convulsions, vomiting and muscle paralysis. However, medicinally, Buttonbush roots and bark were used to treat a variety of ailments including menstrual flow, fevers, kidney stones, diarrhea, constipation and even toothaches.

So, if you’re looking for a hardy, native shrub to plant in your backyard that is aesthetically attractive, attracts wildlife and promotes pollinators, and that requires little to no regular maintenance, the Buttonbush could be your plant! Just remember that it needs to be kept in an area/provided with enough water to ensure the soil stays moist to wet the majority of the time.

Further Reading:

• Buttonbush - Ontario Native Plants 
• The Spruce - How to Grow and Care for Buttonbush: 
• Outdoor Learning Lab - Common Buttonbush
• Wildflower Centre - Buttonbush Profile