Latin Name: Cephalanthus occidentalis
Common Name(s): Buttonwillow, Buttonbush, Honey bells
Family: Rubiaceae
Size: up to 20 feet tall and wide, but usually only around 10. Can take the form of a small tree or bush and responds well to training.
Life Cycle: Perennial, woody
Distribution: Disjunct; in the Western US it is found in California throughout the central valley and in scattered locations in Arizona. Also found in Central Mexico and most of the eastern half of the US.
Light Requirements: Full sun to partial shade
USDA Zone: 5a to 9b
Drought Tolerance: Low. On the West Coast this plant is almost always associated with water
Fire Risk: Presumably low, given the environment this species demands. Will resprout after light burns, which may even enhance growth, but repeated burning will kill most and stunt and slow growth of the survivors.
Cultivation Notes
Buttonbush grows in a wide variety of soils and can take standing water and boggy conditions. It’s primary requirement is moisture: it requires steady moisture and strongly resents drying out. Buttonbush plants can be grown away from water but will require regular irrigation if the soil is not consistently moist. Buttonbush responds very well to pruning and can be cut back hard without dying. Does not require much in the way of fertilizer, but will appreciate mulch to maintain moisture.
Ecology
The peculiar and attractive flowers bloom mid-summer, attracting a wide variety of pollinators. The seeds are eaten by birds and small mammals in the fall and winter. Deer will browse the foliage as well.
Uses
Buttonbush is toxic due to a chemical called cephalanthin. Despite this the plant was used medicinally by Native American peoples, albeit in a carefully controlled manner. The plant is a good honey plant for bees and has been widely planted to stabilize streambanks and prevent erosion. The wood is light and tough but is not used commercially.
Propagation
Propagation can be accomplished with seeds, hardwood cuttings when dormant, and softwood cuttings. Seeds can be sown directly in the fall, winter, or early spring and will often germinate without stratification.
Climate Adaptation
As the climate on the West Coast changes, the potential range of many of our native plant species will change. This fact combined with the possible introduction of the Emerald Ash Borer to Oregon will likely lead to the widespread death of certain riparian species, Oregon Ash in particular. Buttonbush is a riparian species that is extremely flexible and already suitable for both current and predicted climate regimes in the Willamette Valley (and beyond) while providing a wide range of ecosystem services. It provides valuable food and cover for wildlife and is a great candidate for places that suffer from flooding and associated erosion, which plantings of buttonbush can help prevent. It also has not proven invasive here, meaning that its presence in the state may simply increase biodiversity without threatening natives and thus increase the resiliency of the already-threatened Oregonian riparian ecosystems. It is not threatened, however, and has a wide distribution across multiple countries so plantings of buttonbush should not be prioritized over native Oregonian species and rare Californian riparian species. Overall this is an attractive and useful species that is well-worth considering when restoring human-impacted landscapes or creating man-made wetlands.