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.