Buttonbush is a native perennial shrub, named for the round flower heads, which begins to bloom in early summer.
Stems are usually multiple and branched and grow from 3 to 10 feet in height, and higher if grown as a small tree. Bark is smooth on young stems and scaly on older stems. Twigs are green initially, becoming reddish-brown with lighter lenticels.
Leaves are opposite, elliptical in shape, stalked, entire, and 2 to 6 inches long, pointed tips and tapered at the base. The upper surface is smooth and glossy green; the underside is paler color with a few hair on the ribs.
The inflorescence is a single globular head of flowers, on a long stalk from the terminal stem or from a leaf axil.
Flowers: The small white 4-parted tubular flowers that grow out of the round 1 inch wide head have a long protruding style, twice the length of the corolla, which is clearly evident in the photos. The style has a knobby tip. The white corolla forms 4 lips which flare outward slightly. The four stamens have dark anthers and do not protrude from the corolla; the receptacle has fine white hair; the calyx is short and green with 4 teeth; each flower is sessile. The entire head is on a very long stalk (peduncle) from the leaf axil and terminal stem bud.
The seed matures in those round clusters as brown nutlets about 5mm long in the shape of upside down pyramids. Seed dispersal establishes new plants. No special treatment is necessary for seed germination.
Habitat: Buttonbush grows from a woody root system, with a taproot. It prefers moist fertile soil in full sun. It will grow in drier soils and in partial shade but will not flower well unless it receives enough water. Un-rooted cuttings can even establish new plants if other competing vegetation is removed from around the cutting.
Names: The genus Cephalanthus is derived from two Greek words - kephale, meaning 'a head' and anthos, meaning 'a flower', together referring the the rounded flower head. the species occidentalis means 'western' to distinguish the North American species from the other species of Cephalanthus that grow in other parts of the world. The author name for the plant classification - 'L.' is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Comparisons: While some other shrubs have similar leaves and growing habit, the flower heads are distinctive.
Above: 1st photo - The inflorescence is a single flower round flower head on a long stalk. 2nd photo - Seed capsules forming.
Below: 1st photo - Individual flowers have 4 stamens within the white corolla and a slender protruding style that is twice the length of the corolla. The corolla forms 4 lips which flare outward slightly
Below: 1st photo - The corolla turns a reddish-brown at maturity. 2nd photo - The nutlets are in the shape of upside down pyramids, about 5mm long.
Below - Leaves have pointed tips, tapered bases and smooth margins. 1st photo - the upper surface is smooth and glossy green. 2nd photo - The underside is paler in color showing the fine network of veins. There can be a few hair on the midrib as shown here.
Below: Bark of older stems.
Below: One of the large Buttonbush shrubs in the Garden Wetland - the preferred environment.
Below: An example of a specimen growing in a drier landscape environment, which the plant tolerates if given sufficient moisture.
Notes: Eloise Butler's records show that she obtained plants of this species on July 2, 1907 from Malden, Massachusetts. This was where her sister, Cora Butler Pease, lived and to where Eloise would return for summer visits until 1910 and every Winter thereafter. She either collected these herself, or Cora did, and then had them shipped to her in Minneapolis. By 1914 the Park Board Nursery was growing the species and Eloise obtained one there. Martha Crone planted the shrub in 1947 and Gardener Cary George planted the species in 1989 and again in 1994. It is native to Minnesota only in counties on the eastern edge of the state from Pine in the north to Houston in the south with the exception of Goodhue. In North America it is native to all states along and east of the Mississippi River and to most Canadian Provinces to the North of those states. This is the only species of Cephalanthus found in Minnesota.
There are several bushes in the marsh area between Guidebook Stations 23 and 25 where they have the wet areas they grow well. One plant is well over 10 feet high. The plant is delightful to look at but rather coarse. Buttonbush is very beneficial to wildlife. The seeds are eaten by 8 known species of waterfowl and the twigs are eaten to mammals.
Eloise Butler wrote of this plant: "The “buttons” are creamy balls over an inch in diameter, composed of closely packed, small, tubular flowers. A specimen of this interesting plant, with many other species, was shipped from Massachusetts for planting in the wild garden in July of the first year of its founding. The location of the plant was not recorded, and it was supposed to have died out. The next year another plant was obtained, which produced one blossom the following season, and the next summer a dozen or more blooms. While admiring these, a random glance perceived a bush some distance within the swamp luminous with starry globes. It was the first Buttonbush, all covered with buttons à la mode, which had grown to maturity, undetected in the rank vegetation." Published Aug. 20, 1911, Minneapolis Sunday Tribune.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"