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Buttonbush - A Plant in Need of Respect

by Bruce Crawford, Manager of Horticulture, Morris County Park Commission
Zoom in Cephalanthus occidentalis shrub.
Picture 1: Flowers on a mature shrub.

To borrow and slightly adjust a phrase from Mr. Rodney Dangerfield's comedic repertoire: "Some plants get no respect"! The irony for these belittled or overlooked plants is how many are easily grown, even under challenging conditions and how many are native! Part of the problem lies in the timing of the floral display. Plants blooming outside of the spring rush to garden centers usually do not garner their duly deserved respect. Another issue is the limited amount of promotion for plants that thrive in truly challenging sites, such as boggy or frequently flooded areas. Such is the problem that plagues our native Buttonbush, botanically known as Cephalanthus occidentalis as seen in Picture 1.

Cephalanthus is a member of the Rubiaceae or Madder Family, the fourth largest flowering plant family with the majority of the 620 genera native to tropical locations. Probably the most recognized member of this family is the genus Coffea or coffee! Cephalanthus contains a total of 6 species that are found in North and South America, Africa, and Asia. Cephalanthus occidentalis has an impressively large native range, stretching from New Brunswick Canada, west to Wisconsin and south to Florida and central Mexico with isolated populations in Cuba, California and eastern Asia! The genus and species were named in 1753 by the Swedish Botanist Carl Linnaeus (1707–1778). The genus name was inspired by the rather unique globe shape of the flowers and is a combination of the Greek Kephale for head and Anthos meaning flower. The species epithet is from the Latin for west, and for those living in Europe, eastern North America is indeed to the west! The common name is derived from the resemblance of the flowers to the globe shaped dress buttons common during the 1700's.

Zoom in Cephalanthus occidentalis 'Sugar-Shack' in July.
Picture 2: Flower buds with leafy calyces at their base.

With so much of the plant's name focused on the flower, one can only assume the flower is truly unusual – and so it is! Come July and August, the fragrant white flower clusters appear at the end of branches (as seen in Picture 1), with each 1–1½" diameter globe composed of roughly 200 individual florets. At the center is a densely packed cluster of calyces that in turn are perched upon a central cluster of ovaries. Each calyx consists of 4 leafy green sepals that are fused into a tube and from which the trumpet shaped white florets emerge (Picture 2). Each ½" long floret consists of 4 white petals with rounded tips that peel backward, exposing the 4 light brown anthers secured to the points where the open petals meet. The tissue that initially connects the anthers to the petals is dark brown in color and appears as tiny black dots on the outside of the flower bud (as again seen in Picture 2). Lining the center of each petal are small hairs, which may serve to keep the various pollinators close to the center of the female style and moving in a circular motion about the flower, ensuring they will come in contact with a pollen shedding anther. The dramatic and attention-grabbing portion of the flower is the female style and terminal stigma. Protruding a full ¼–⅜" beyond the flower, the style and stigma give the flower its very dramatic spikey appearance as seen in Picture 3 and Picture 7.

Zoom in Cephalanthus occidentalis close-up.
Picture 3: Close-up of florets.

The flowers can easily be seen from a distance and the protruding styles give the plant an 'other worldly' appearance. Each floral globe only blooms for 3–4 days, but the numerous flower buds ensure several weeks of bloom. The flowers are highly attractive to various pollinators including numerous Butterflies, the Hydrangea and Titan Sphinx Moths as well as Hummingbirds. In fact, as early as 1735 the plant was described as being noteworthy for beekeepers. If that was not enough, the foliage supports the larval stages of the Hydrangea and Titan Sphinx Moths.

Following pollination, the central core of calyces and ovaries persist and enlarge, ultimately providing a rather interesting 1" globe lasting well into winter. Come late August and into the fall months, the calyces gradually assume hues of red and reddish brown (as seen in Picture 4), once again adding an interesting ornamental touch. Each individual flower within the globe ultimately produces a dry fruit defined as a schizocarp; this fruit in turn splits open during late winter yielding 2 seeds that are beloved by ducks and seed loving birds.

The overall shape or habit of the shrubs varies from rounded to upright oval. Plants usually grow to 6–8' tall and wide, but can reach heights and widths of 12–15'. In the wild, the plants often form thickets in lowlands or along the edge of ponds, often with the plant partially submerged in water! Clethra alnifolia or Pepperbush is often found growing in association with Buttonbush. The best flower production and fall color occurs in full sun, although plants are tolerant of light shade. As one would expect from a plant having a very diverse native range, it also has a broad hardiness range, growing well in zones 4–11. The plant is one of the last plants to leaf out in spring, with the glossy dark green foliage (Picture 5) typically not appearing until mid-May. The elliptically shaped leaves are arranged oppositely or occasionally in whorls of three and vary from 2–6" long by roughly ½ as wide. Fall color varies from an unremarkable tan to bright yellow to stunning oranges, reds and maroons depending upon the plant. The plants also have a moderate tolerance to deer browse.

Zoom in Cephalanthus occidentalis in August.
Picture 4: The globe of calyces turning red come fall.
Zoom in Cephalanthus occidentalis foliage.
Picture 5: Glossy foliage in August.

Of the selections currently on the market, the selection named 'Bieberich' that is better known under the trademarked name of Sputnik™ undoubtedly has the most descriptive name. Discovered by Steve Bieberich of Sunshine Nursery from a native population in Oklahoma, the plant has light pink flowers which are vaguely reminiscent of the first satellite launched by the Soviet Union in 1957. Growing to 10–15' tall and wide, the foliage turns an attractive coppery bronze come fall.

Zoom in Cephalanthus occidentalis.
Picture 6: Sugar Shack® in bloom.

Another great selection is Sugar Shack®. Growing to a more diminutive size of 4–5' tall and wide, it is more appropriately sized for residential gardens (Picture 6). It produces the typical white flowers over glossy, dark green foliage. Often, the flushing foliage in spring into summer has an attractive orange blush. The foliage would pair very nicely with Diervilla lonicera 'Copper' (Northern Bush Honeysuckle) in the garden. Following bloom, the spherical fruit clusters turn a very bold and attractive red. Come fall, the foliage continues the colorful display with a saturnalia of colors, ranging from pink to red to burgundy. Another compact form with a wonderfully romantic name is Magical® Moonlight. It too grows to 4' tall and 4–5' wide.

Interestingly, fossils of a now extinct species named Cephalanthus pusillus have been found in Germany dating back to 40 Million Years Ago (MYA). Although far from being classified as one of the oldest plants on earth, its age on earth and adaptability helps to explain the global reach of this genus! Button Bush is a plant few gardeners have yet to discover and it certainly comes as no surprise. Shrubs blooming in July and August are easily overlooked by spring shoppers who are bedazzled by the variety of spring and early summer bloomers. If only more shoppers returned to the garden center come mid-summer to see what is currently in flower. I remain ever hopeful gardeners will discover and appreciate the beauty of this mid-summer bloomer and place it in the garden where it will receive the respect it so deserves!

Close up in July.
Picture 7: Floral globe in July.