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Published In: Species Plantarum 1: 95. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library
 

Project Name Data (Last Modified On 9/8/2017)
Acceptance : Accepted
Project Data     (Last Modified On 7/9/2009)
Status : Native

 

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1. Cephalanthus occidentalis L. (buttonbush, globe flower, honeyball, pond dogwood)

C. occidentalis var. pubescens Raf.

Pl. 545 e, f; Map 2532

Plants shrubs or small trees, 1.5–5.0 m tall. Stems somewhat angled to rounded, glabrous, the twigs sometimes finely short-hairy. Leaves variously opposite or in whorls of 3 per node, the petioles 10–25 mm long. Stipules interpetiolar, 2–4 mm long, triangular, generally persisting with the leaves, angled to a sharply pointed tip, sometimes with minute fingerlike glands on the margins. Leaf blades 2.5–16.0(–23.0) cm long, 2–6(–10) cm wide, elliptic to elliptic-oblong or ovate, angled or slightly tapered to a sharply pointed tip, rounded or angled at the base, the margins flat, the upper surface glabrous, sometimes shiny, the undersurface glabrous or with small tufts of hair in the vein axils, occasionally more uniformly short-hairy, the midvein and 6–8 pairs of secondary veins visible. Inflorescences dense, globose heads 1–4 cm in diameter, in a loose terminal cluster and sometimes also solitary from the uppermost leaf axils, each with a stalk 1.5–6.0 cm long. Flowers homostylous, numerous, intermingled with short, linear to narrowly club-shaped bracts. Calyces 0.8–1.1 mm long, persistent at fruiting, 4-lobed, the lobes 0.4–0.5 mm long (becoming enlarged to 1.0–1.5 mm at fruiting), rounded at the tips. Corollas 9.0–12.5 mm long, narrowly funnelform to nearly cylindric, white, externally glabrous, internally pubescent with short wavy hairs in upper part of the tube and sometimes also the lobes, the tube 7–10 mm long, 4-lobed, the lobes 1.5–2.5 mm long, narrowly elliptic, bluntly pointed at the tips. Stamens 4, the anthers exserted. Ovary fully inferior, 2-locular, the ovules 1 per locule. Style 1, the stigma 1, cylindric, exserted. Fruits apparently multiple in a single globose mass but at maturity separating from each other, the individual fruits schizocarps, 5.0–5.5 mm long, 1.5–2.0 mm wide, dry, narrowly obconic, at maturity splitting from the base into 2 mericarps. 2n=44. June–August.

Scattered to common throughout the state (eastern U.S. west to Minnesota and Texas, also Arizona, California; Mexico, Central America, Caribbean Islands). Swamps, sloughs, oxbows, bottomland forests, banks of streams, rivers, and spring branches, margins of ponds, lakes, and sinkhole ponds, and marshes; also ditches, pastures, railroads, and wet roadsides; sometimes emergent aquatics.

The leaves vary notably in number per node, size, shape, petiole length, and pubescence. Cephalanthus occidentalis can be reliably recognized even without flowers, however, as our only Rubiaceae shrub, that is, our only shrub with entire leaves and interpetiolar stipules. The stipules are sometimes shed toward the end of the growing season, but usually at least a few persist on the younger stems.

Buttonbush is occasionally cultivated as an ornamental and for pond-bank stabilization, and also is a good bee-plant. Steyermark (1963) noted that: “the leaves contain a bitter substance used in medicine. A tea made from the root of the bark has sometimes been employed in the treatment of diabetes. Animals may be poisoned by feeding on the leaves.” Old shrubs, particularly in sinkhole pond communities, tend to develop hummocky bases, on which a characteristic herbaceous flora develops, notably Carex decomposita Muhl., an unusual species of Cyperaceae.

Some authors have separated two varieties within this species: var. pubescens has been distinguished by its leaves and young twigs having at least sparse pubescence (vs. glabrous in var. occidentalis). The var. pubescens is most often found in the southeastern U.S., including southeastern Missouri (Steyermark, 1963). However as noted by various authors, pubescent plants are found sporadically more or less throughout the range of the species. And, as discusssed by Steyermark, there is a wide and continuous range of pubescence density among individual plants. Thus these varieties are not recognized here. The occurrence of tufts of hairs in the axils where the secondary veins meet the midvein on the leaf underside is a common feature in woody Rubiaceae species, and one whose occurrence is known to be independant of other pubescence. These tufts are known as acarodomatia, that is, structures that shelter very tiny mites. These mites pay for their shelter by cleaning the plant’s leaves of attackers such as fungal spores, which they eat.

 


 

 
 
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