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.