Herbs, subshrubs, shrubs, or trees, (rarely vines), perennial, deciduous or evergreen, usually autotrophic, sometimes mycotrophic (subfam. Monotropoideae), usually chlorophyllous and autotrophic, sometimes achlorophyllous and heterotrophic (subfam. Monotropoideae), aromatic compounds (e.g., methyl salicylate) sometimes present (Gaultheria). Stems (absent in some Monotropoideae) erect or decumbent to prostrate, glabrous or hairy, (aerial stems sometimes produced from suckers, rhizomes, or corms), pith solid (hollow, with diaphragms in Agarista). Leaves (reduced or absent in some Monotropoideae), usually cauline, sometimes in basal rosettes (subfam. Monotropoideae), usually alternate or pseudoverticillate, sometimes opposite or, rarely, whorled, simple; stipules absent; petiole present or absent; blade plane or acicular, often coriaceous, margins entire or toothed, plane or revolute. Inflorescences terminal or axillary racemes, umbels, corymbs, panicles, fascicles, spikes, or solitary flowers. Flowers usually bisexual, rarely unisexual (subfam. Ericoideae), radially symmetric (sometimes slightly bilaterally symmetric in subfam. Monotropoideae and subfam. Ericoideae); perianth and androecium hypogynous (epigynous in some Vaccinioideae); hypanthium absent; sepals absent or (2-)4-5(-7), distinct or connate basally; petals (2-)4-5(-8), rarely absent or highly reduced, connate or distinct, not sticky (covered with sticky exudate in Bejaria), corolla absent or rotate to crateriform, campanulate, cylindric, globose, or urceolate (salverform in Epigaea); intrastaminal nectary disc present or absent; stamens (2-)5-8(-10) [14, 16, 20]; filaments distinct; anthers inverted during development, often with awns, dehiscent by pores or short slits (at apparent apex) or slits (lateral); pistils 1, 4-5-carpellate; ovary superior (inferior in some Vaccinioideae), incompletely (2-)5-10-locular (1-locular in some Monotropoideae), often furrowed or lobed externally; placentation axile or parietal; ovules anatropous, unitegmic, tenuinucellate; styles 1, straight or declinate (curved in Elliottia), hollow; stigmas 1, capitate or peltate to funnelform, usually 5-lobed. Fruits capsular and dehiscent (loculicidal, septifragal, or septicidal), or drupaceous (axis fibrous or soft in some Monotropoideae) or baccate (rarely each surrounded by accrescent or fleshy calyx in Gaultheria) and indehiscent. Se

The closest relatives of the broadly defined Ericaceae are Clethraceae and Cyrillaceae. Some phylogenies show Cyrillaceae as sister to Ericaceae; other analyses have Clethraceae and Cyrillaceae as closest relatives to each other, together forming the sister group to Ericaceae. Monotropa and related genera (genera 5-12 of this treatment), and Pyrola and related genera (genera 1-4 of this treatment) have been treated as families Monotropaceae and Pyrolaceae. Not all botanists agreed with this, as summarized by G. H. M. Lawrence (1951): 'Many botanists (including Hutchinson) have held the view that the Pyrolaceae are not sufficiently distinct from the Ericaceae to be treated as a separate family.' Differences in habit, floral features, and pollen have helped maintain family status for Pyrolaceae and Monotropaceae in regional floras. Molecular and morphological analyses (K. A. Kron et al. 2002) show these lineages embedded within Ericaceae. Similarly, Empetraceae has been demonstrated to be nested within Ericaceae and is here included in the Ericaceae.

P. F. Stevens (2004) recognized eight subfamilies within Ericaceae; six of these are represented in the flora area. Subfamily Enkianthoideae, basal in recent phylogenies of the family, forms a sister clade to the remaining subfamilies. The subfamily includes only the single genus Enkianthus Loureiro (12 species), native to temperate eastern Asia. Enkianthus campanulatus (Miquel) G. Nicholson is cultivated occasionally in the northeastern and northwestern United States (M. A. Dirr 1998). Subfamily Styphelioideae Sweet (subfam. Epacridoideae Arnott) of the Southern Hemisphere (especially diverse in Australia with such genera as Astroloma R. Brown, Epacris Cavanilles, and Styphelia Smith), long considered a close relative of the Ericaceae, has been demonstrated as embedded within the Ericaceae. As G. H. M. Lawrence (1951) noted, distinctions between the two families are weak.

Studies in the last several decades, especially since 1990 including molecular data, have resulted in rearrangements of generic limits in the Ericaceae. These are discussed under the various genera; for the reader´s convenience they are summarized here. Ledum is included in Rhododendron; Leiophyllum and Loiseleuria are included in Kalmia; and Hypopitys is included in Monotropa. Arctous is separated from the much larger Arctostaphylos, to which it is inferred to form a sister clade. Eubotrys is segregated from Leucothoe, with which it has often been combined. Vaccinium is treated in a broad sense, to include segregates such as Oxycoccus; although Vaccinium is decidedly polymorphic, this seems a workable approach until generic limits in the Vaccinieae Reichenbach are better understood.

Most Ericaceae are evergreen shrubs. Some species are deciduous, notably in Rhododendron and Vaccinium. The propensity of members of the family to grow in acidic soils is well known. Although the family Ericaceae is generally regarded as exclusively growing on acidic substrates, some members of the family do occur in neutral or alkaline soils in North America and elsewhere.

Ericaceae are widely distributed in the Northern Hemisphere, almost ubiquitous except in desert areas. In the tropics, especially in South America, the family is diverse in upland and montane areas, and notably diverse in such genera as Bejaria and Cavendishia Lindl