Buttonbush Growing, Planting, Facts & Care (Cephalanthus occidentalis)
A deciduous shrub that favors wetland habitats, Cephalanthus occidentalis would make a great addition to rain gardens. It is commonly known as buttonbush, little snowballs, honeybells, white pond-dogwood, swamp globeflower, and button-willow. It is one of just six Cephalanthus species, among which it is the most widely cultivated. It is classified under the large Rubiaceae family of easily recognizable flowering plants, including those that produce coffee beans (Coffea spp.).
Buttonbush is native to North America. It comes in two varieties with separate distributions throughout its native range. C. occidentalis var. occidentalis is found throughout eastern North America, with a range that goes as far north as Nova Scotia. C. occidentalis var. californica is found further south and west, with populations extending into California and Mexico.
Rich in character and seemingly playful elements, buttonbush can be cultivated as a small tree as it grows to a height of about 10 – 15 feet (3 – 4.5 m). Its oppositely arranged leaves are dark green, smooth-edged, and broad, but the spherical inflorescences are the true stars of the show. The tiny flowers are densely packed together and are distinguished by tube-shaped corollas topped with protruding yellow stigmas.
Facts, Benefits & Uses of Buttonbush
Due to its preference for moist conditions, buttonbush can be reared next to a pond. Its summer flowers, which are likened to pincushions, can attract many pollinators to your garden. Hummingbirds, bees, and butterflies favor its sweet nectar. It serves as a plant host to the larvae of Titan sphinx (Aellopos titan) and hydrangea sphinx (Darapsa versicolor) moths. Waterfowl and songbirds benefit from the showy fruits. As the button-like seed heads are able to persist through winter, they serve as a vital food source.
Buttonbush is fairly resistant to fire, heat, excessively damp conditions, and grazing by herbivores. It is not prone to pest infestations and diseases, so it would be a great candidate for native gardens in the US. Its dense branches and foliage can provide shade and serve as natural shelters. To maximize its benefits, try to cultivate this plant in areas with poor drainage or high erosion rates.
If you find that buttonbush shrubs may be too tall for your garden, you’ll be glad to know that this species has dwarf cultivars! ‘Sugar shack’, ‘Ping pong’, ‘Kolmoon’, and ‘Bailoptics’ are compact forms that should generally grow to less than 8 feet (2.4 m) at maturity.
Buttonbush Growth, Hardiness & Climate
C. occidentalis has a low tolerance for drought conditions, so it must be planted close to a consistent source of water. If your garden does not contain any water features, the soil around the plant must constantly be irrigated. The roots can tolerate flooding events and can even survive when submerged in up to 3 feet (1 m) of water.
In the wild, buttonbush shrubs are usually found in shrub plains, riparian zones, swamps, and mangrove forests. Once established, they can serve as windbreakers that help protect smaller plants. Cuttings are sometimes used as live stakes to reinforce stream banks. Wild plants are often found in thickets, with the oldest trees looking quite mangled due to their twisted trunks and abundance of branches. Their roots spread via underground suckers from which new shrubs may arise.
Hardy to USDA zones 5 – 9, buttonbush prefers a temperature range of 16 – 24˚C (61 – 75˚F). It thrives best when cultivated in rich soil and under full sunlight. Note that under partial sun, flowering rates can become drastically reduced.
How to Plant Buttonbush
C. occidentalis can be planted using its seeds or cuttings. If freshly collected from a tree in the fall, the seeds can be planted directly into the ground. They will not require stratification but should be provided with some protection from competing plants and harsh winter conditions. Simply spread them evenly over consistently moist, humus-rich soil in pots that are placed in a greenhouse, cold frame, or sheltered part of the garden.
As the seedlings grow larger, you may need to transplant them into appropriately sized containers. You may plant them directly outdoors if ambient conditions are mild. Once the seedlings are a year old, they should be spaced at least 2 – 4 feet (0.6 – 1.2 m) apart to make room for their roots to spread. If you’re using the plant for wetland development or erosion control, wider spacing may be preferable.
To collect cuttings, remove about 2 – 6 inches (5 – 15 cm) of terminal stem segments. These should ideally include a node and a few leaves. Once you’ve removed the lower leaves, dip the exposed bottom part into a cup with rooting hormone. Firmly plant the cuttings into moistened soil mix (ideally one with peat and perlite). Place the planted cuttings in an area with filtered or indirect light until they have produced new roots. In warmer areas, newly rooted cuttings can be out-planted throughout the year.
How to Care for Buttonbush
To ensure that seedlings survive, eliminate competitive grasses and weeds nearby. Always keep the soil around the plant moist. To encourage the roots to spread even further, the range of moisture should expand beyond the plant’s above-ground features. If water levels are low (due to seasonal fluctuations) or you are unable to irrigate your garden, mature plants may survive if their branches are trimmed back.
Pruning is generally unnecessary. It may be more important to prune nearby bushes that outgrow your buttonbush and cast shade on it. For optimal flowering rates, try to ensure that the plant receives full sun all throughout the year. A slow-release fertilizer can also help increase flowering and seed production rates.
Buttonbush is not typically associated with any known pests, but it is advisable to regularly monitor the foliage for insects that may consume the leaves. Established plants will likely survive through minimal leaf consumption by larvae, but seedlings may struggle.
How to Winter Buttonbush
As C. occidentalis is naturally found in areas with cool winters, it does not have major overwintering requirements. This species can tolerate temperatures that dip to -25˚C (-13˚F) for a brief period of time. Those that are situated in large pots may be more sensitive to cold temperatures as the roots are less protected. Try to place these pots on elevated structures that can separate the pot bottom from frozen ground.
Mulching will benefit the root ball of the plant and help retain trace amounts of moisture in the soil. Don’t worry if you begin to see the leaves drop off once temperatures start to cool significantly. They will naturally grow back, along with new buds, the following spring.
Is Buttonbush Invasive or Toxic?
Buttonbush has the tendency to spread and create dense colonies due to its suckering root system. Mature plants can spread to a width that is similar to their height. Despite its capacity to self-propagate, it is not considered an invasive plant. In fact, its spread tends to be more limited when there are competitive plants nearby. It is often recommended as a non-invasive, native alternative to the invasive orange eye butterfly-bush (Buddleja davidii).
It’s important to note that buttonbush leaves and bark contain a toxic compound called cephalanthin, which is a bitter glycoside. When ingested, side effects include nausea, gastrointestinal problems, convulsions, and paralysis. The wilted leaves are known for being especially toxic to pets and herbivorous livestock.
Is Buttonbush Edible? Do Animals Eat it?
C. occidentalis is not considered an edible plant due to its toxic contents. The Native Americans, daring as they were when it came to using all sorts of herbal remedies, did manage to create therapeutic decoctions of the plant. These supposedly helped with a wide variety of digestive ailments, including dysentery, diarrhea, and constipation. This was likely due, in part, to the calming effects of very low doses of buttonbush extracts.
Grazing animals generally avoid this bitter-tasting plant. Birds are able to consume the seeds without harm, and moth larvae happily feed on the leaves.
Where to Buy Buttonbush & Seeds? (UK & US)
Cephalanthus occidentalis can be purchased as seeds, seedlings, and plug plants from garden centers and plant nurseries within its native range. ‘Keystone’ is a cultivar that plant nurseries often carry. Online plant shops usually carry potted options for this plant each spring. If located outside of the US, you might have better luck acquiring seeds. Always check your locality’s legal requirements or prohibitions on importations before purchasing foreign plants.