ERICACEAE (Heath or Blueberry Family)
Contributed by
David J. Bogler
Plants shrubs or
small trees, sometimes evergreen, less commonly mycotrophic (receiving nutrients
and water from associations with soilborne fungi) herbs lacking chlorophyll.
Leaves alternate, simple, often somewhat thickened and leathery, sometimes
reduced to scales, sessile or short-petiolate. Leaf blades simple, the margins
entire or finely toothed. Stipules absent. Inflorescences terminal or axillary,
mostly racemes, the flowers sometimes solitary, subtended by small bracts.
Flowers actinomorphic to slightly zygomorphic, perfect, hypogynous or
epigynous. Calyces deeply 5-lobed or of 4 or 5 free sepals (sometimes absent in
Monotropa), usually persistent at fruiting. Corollas usually 5-lobed or
of 3–6(–8) free petals, trumpet-shaped or tubular to urn-shaped. Stamens mostly
5 or 10, the filaments free or attached to the corolla base, the anthers
attached more or less medially, becoming inverted during development such that
the base becomes the apparent tip, sometimes with scalelike spurs near the
filament-anther junction and/or awnlike extensions at the apparent anther tip,
dehiscing mostly by pores near the apparent tip, these sometimes elongated and
appearing slitlike. Pollen usually released in tetrads (groups of four) (except
in Monotropa) and with viscin strands (sticky, cobwebby strands
connecting the tetrads so the pollen tends to be shed in clumps). Pistils of
usually 5 fused carpels. Ovary superior or inferior, with 1–10 locules, hollow
and fluted, with axile or deeply intruding parietal placentation. Style 1 per
flower, the stigma capitate to disk-shaped, sometimes (4)5-lobed. Ovules 1 to
numerous. Fruits capsules or berries. Seeds 1 to numerous, usually small,
sometimes winged. About 100 genera, about 3,000 species, nearly worldwide,
often on acidic soils.
In the broad
sense, the Ericaceae are a large and morphologically diverse family that
includes trees, shrubs, epiphytes, and herbs. The group is so diverse that some
botanists have broken it up into smaller families or subfamilies (Steyermark,
1963; Cronquist, 1981, 1991). Vaccinium and Gaylussacia sometimes
have been segregated by a few workers as Vacciniaceae, along with other
non-Missouri genera having an inferior ovary. Monotropa and related
genera lacking chlorophyll have been placed in the Monotropaceae or have been
included along with Pyrola (wintergreen) and other mycorrhizal but
green, non-Missouri genera in the Pyrolaceae. The consensus of recent
morphological and molecular studies is that these genera are indeed related and
are best included in a single family (Stevens, 1971; Wallace, 1975; Judd and
Kron, 1993; Kron, 1996), and the present treatment therefore deviates from the
general practice in this manual of following Cronquist’s (1981, 1991) familial
classification system.
The Ericaceae
are an economically important family. The genus Vaccinium is the source
of blueberries and cranberries. A number of genera are cultivated as
ornamentals, including Arctostaphylos (bearberry), Epigaea
(trailing arbutus), Erica (heath), Kalmia (mountain laurel), Pieris
(pieris, fetterbush), Rhododendron (azalea, rhododendron), and Vaccinium
(there are also several additional genera not hardy in Missouri). All of the
cultivated taxa require acidic soils, which makes them difficult to grow at
many locations, given the widespread calcareous substrates in the state.