Ericaceae
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. Seeds 1–10(–1000+), tan to yellowish brown or brown, ellipsoid, ovoid or spheroidal, or fusiform to flattened, or oblong (sometimes 3-sided); testa thin (bony in subfam. Arbutoideae and subfam. Vaccinioideae); embryo usually straight, fusiform, rarely minute and undifferentiated; endosperm abundant, cellular, fleshy.
Contents
Distribution
Nearly worldwide.
Discussion
Genera ca. 120, species ca. 4100 (46 genera, 212 species in the flora).
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 Leucothoë, 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 Lindley. Rhododendron, with centers of diversity in the Himalayas, New Guinea, and eastern North America, and Erica, diverse in southern Africa and Europe, are the largest genera in the family. The largest genus in the flora area is Arctostaphylos, with most species endemic to California and bordering states.
Species among some genera of the family enrich the human condition with edible fruits. In North America, by far the most important of these is Vaccinium. The high-bush blueberry, V. corymbosum, is cultivated in some states, notably Michigan, New Jersey, and North Carolina, and the low-bush blueberry, V. angustifolium, in Maine, Quebec, and the Canadian Maritime Provinces. The fruits of V. macrocarpon, the cranberry, are cultivated commercially in some provinces, including British Columbia, Nova Scotia, and Quebec, and some states including Massachusetts, Oregon, Rhode Island, Washington, and Wisconsin. Vaccinium vitis-idaea, lingonberry, is collected and sold in Newfoundland and Labrador as fresh fruits and preserves, and is an important addition to diet and health in the more northern areas of Canada. The leaves of Rhododendron groenlandicum (Ledum groenlandicum), Labrador tea, are used for a beverage in parts of its transcontinental range. The foliage of some genera, notably Leucothoë, Lyonia, and Rhododendron, contains andromedotoxins and is occasionally implicated in poisonings of humans, domestic pets, and livestock (J. M. Kingsbury 1964; S. D. Mancini and J. M. Edwards 1979). Kalmia also is reportedly toxic, perhaps why it is called sheep laurel, in addition to probably being allelopathic and thus detrimental to reforestation in some situations in the eastern boreal forest. Lyonia ferruginea is a valuable “forest product” in Florida. It is harvested and the stems are used in interior decoration; once silk leaves have been added, they are marketed as “artificial” plants.
Some species of Ericaceae, both native and exotic, are cultivated and of importance to the horticultural industry (M. A. Dirr 1998). Chief among these are Kalmia and Rhododendron (including many deciduous species known as “azaleas”). Other cultivated genera include Arbutus, Elliottia, Enkianthus, Leucothoë, Menziesia, Oxydendrum, and Pieris. Rock garden plants include Arctostaphylos uva-ursi, Kalmia buxifolia, K. procumbens, and Rhododendron lapponicum, as well as species of the Old World genera Calluna and Erica. Shrubs of some genera, including Gaultheria, Gaylussacia, and Vaccinium, are prominent in the understories of deciduous and evergreen forests, especially in regions of acidic soil, such as the southeastern United States. Wetlands in much of Canada and the northern United States support dense populations of ericaceous shrubs, notably Andromeda polifolia and Chamaedaphne calyculata; Kalmia spp., Rhododendron canadense, and R. groenlandicum may be as prominent depending on the region.
Selected References
Lower Taxa
Illustrations
Keys
Synoptic Key to Subfamilies
| 1 | Plants achlorophyllous, heterotrophic, herbaceous; leaves absent or reduced, scalelike, blade plane; inflorescences racemes; fruits not fleshy | Ericaceae subfam. Monotropoideae |
| 1 | Plants chlorophyllous, autotrophic, woody or herbaceous; leaves not reduced, blade plane or acicular; inflorescences usually fascicles, racemes, panicles, spikes, umbels, or corymbs, sometimes solitary flowers; fruits fleshy or not | > 2 |
| 2 | Plants herbs or subshrubs; leaves persistent, mostly basal (reduced or absent); petals distinct; fruits capsular and dehiscence loculicidal or baccate and indehiscent | Ericaceae subfam. Monotropoideae |
| 2 | Plants vines, subshrubs, shrubs, or trees; leaves deciduous or persistent, cauline; petals connate or distinct; fruits capsular and dehiscence loculicidal or septicidal (sometimes septifragal) or baccate or drupaceous and indehiscent | > 3 |
| 3 | Fruit pulp ± juicy or mealy; pyrenes with stonelike endocarp, seeds 1-5, sometimes connate; corollas usually urceolate, sometimes cylindric; bark smooth, not furrowed, usually flaky | Ericaceae subfam. Arbutoideae |
| 3 | Fruit pulp ± juicy or dry; testa thin, rarely surrounded by bony endocarp, seeds (1-)10 (-300), distinct; corollas rotate, campanulate, cylindric, or urceolate (rarely salverform), sometimes absent; bark smooth or furrowed, not flaky | > 4 |
| 4 | Subshrubs; leaves persistent; inflorescences solitary flowers; (arctic and alpine regions) | > 5 |
| 4 | Shrubs (rarely vines, subshrubs, or trees); leaves deciduous or persistent; inflorescences fascicles, racemes, panicles, or spikes (rarely solitary flowers) | > 6 |
| 5 | Inflorescences axillary; leaves opposite | Ericaceae subfam. Cassiopoideae |
| 5 | Inflorescences terminal; leaves alternate | Ericaceae subfam. Harrimanelloideae |
| 6 | Shrubs (subshrubs or trees); ovaries superior; fruits, when dehiscent, usually septicidal, sometimes loculicidal or septifragal capsules; corollas sometimes persistent; seeds winged or not | Ericaceae subfam. Ericoideae |
| 6 | Vines, shrubs, or trees; ovaries inferior or superior; fruits, when dehiscent, loculicidal capsules; corollas deciduous; seeds usually not winged, sometimes slightly winged | Ericaceae subfam. Vaccinioideae |
Key to Genera
| 1 | Plants achlorophyllous; leaves reduced or absent | > 2 |
| 1 | Plants chlorophyllous; leaves usually present | > 10 |
| 2 | Flowers bilaterally symmetric. | Pyrola |
| 2 | Flowers radially symmetric | > 3 |
| 3 | Ovaries 1-locular; fruits baccate (fleshy); inflorescence axes not fibrous, not persistent | > 4 |
| 3 | Ovaries (4-)5(-6)-locular; fruits capsular; inflorescence axes fibrous, persistent after seed dispersal | > 7 |
| 4 | Petals connate | > 5 |
| 4 | Petals distinct | > 6 |
| 5 | Inflorescence axes violet to purple; e United States | Monotropsis |
| 5 | Inflorescence axes pink to cream; Pacific Coast (British Columbia to California). | Hemitomes |
| 6 | Petals glabrate abaxially, pubescent adaxially; anthers horseshoe-shaped; stigmas umbilicate, subtended by ring of hairs. | Pityopus |
| 6 | Petals glabrous; anthers elongate; stigmas crownlike, without subtending ring of hairs. | Pleuricospora |
| 7 | Petals connate; fruits dehiscent acropetally or indehiscent to irregularly dehiscent; seeds ovoid | > 8 |
| 7 | Petals distinct; fruits dehiscent basipetally; seeds fusiform | > 9 |
| 8 | Inflorescence axes pink to reddish or brownish, 0.5-1.5 cm diam. at proximal flower; anthers with awns; fruits dehiscent; seeds winged (with broad, rounded, membranous wing attached at 1 end). | Pterospora |
| 8 | Inflorescence axes bright red to dark orange, 2-10 cm diam. at proximal flower; anthers without awns; fruits indehiscent to irregularly dehiscent; seeds not winged. | Sarcodes |
| 9 | Inflorescence axes white with red to maroon vertical stripes; pedicels erect; sepals usually absent, rarely 2-5; stamens exserted. | Allotropa |
| 9 | Inflorescence axes white or yellowish to orange or reddish; pedicels decurved to spreading at anthesis; sepals (3-)4-5(-6); stamens included. | Monotropa |
| 10 | Herbs or subshrubs; leaves basal (or appearing so), or cauline and alternate or pseudoverticillate; petals distinct | > 11 |
| 10 | Trees, shrubs, subshrubs, or vines; leaves cauline, usually alternate, rarely opposite, pseudoverticillate, spirally arranged, or whorled; petals usually connate, rarely distinct or absent | > 14 |
| 11 | Inflorescences solitary flowers or 2-7-flowered corymbs or subumbels; fruits with no cobwebby tissue exposed by splitting valves at dehiscence | > 12 |
| 11 | Inflorescences solitary flowers or 2-29-flowered racemes; fruits with cobwebby tissue exposed by splitting valves at dehiscence | > 13 |
| 12 | Inflorescences solitary flowers; filaments glabrous; styles exserted; stigmas 5-lobed. | Moneses |
| 12 | Inflorescences 2-7-flowered corymbs or subumbels, rarely solitary flowers; filaments ciliate or villous basally; styles included; stigmas entire or obscurely 5-ridged. | Chimaphila |
| 13 | Inflorescences symmetric, usually erect; petals without basal tubercles. | Pyrola |
| 13 | Inflorescences secund (becoming ± erect in fruit, often lax in bud or flower); petals with 2 inconspicuous, basal tubercles. | Orthilia |
| 14 | Ovaries inferior; fruits fleshy | > 15 |
| 14 | Ovaries superior; fruits fleshy or not | > 16 |
| 15 | Fruits baccate; seeds 2-40, testa thin. | Vaccinium |
| 15 | Fruits drupaceous; seeds 10, testa bony (pyrenes). | Gaylussacia |
| 16 | Petals distinct or connate to 1/4 their lengths | > 17 |
| 16 | Petals connate 1/3+ their lengths (absent in Corema) | > 22 |
| 17 | Petals 7, covered by sticky exudate; (Alabama, Florida, Georgia). | Bejaria |
| 17 | Petals 2-5, not sticky | > 18 |
| 18 | Leaves whorled; fruits dry, red; pyrenes 2. | Ceratiola |
| 18 | Leaves alternate or opposite (sometimes whorled); fruits capsules, without pyrenes | > 19 |
| 19 | Sepals 3; fruits drupaceous. | Empetrum |
| 19 | Sepals (4-)5; fruits capsules | > 20 |
| 20 | Styles usually curved, sometimes straight; (Pacific Northwest coast, Georgia, South Carolina). | Elliottia |
| 20 | Styles straight (if bent or curved, then leaves alternate) | > 21 |
| 21 | Petals pink; flowers usually slightly bilaterally symmetric; leaves deciduous. | Rhododendron |
| 21 | Petals white or pink, flowers radially symmetric; leaves persistent (K. cuneata deciduous). | Kalmia |
| 22 | Flowers unisexual or bisexual | > 23 |
| 22 | Flowers bisexual | > 24 |
| 23 | Corollas ± salverform; leaves alternate; fruits capsular; inflorescences spikes or dense racemes. | Epigaea |
| 23 | Corollas inconspicuous or absent; leaves whorled or opposite (sometimes spiral); fruits drupaceous; inflorescences usually capitula, cymes, or fascicles, sometimes solitary flowers. | Corema |
| 24 | Fruits enclosed by fleshy calyx; leaves aromatic. | Gaultheria |
| 24 | Fruits enclosed by nonfleshy calyx; leaves not aromatic | > 25 |
| 25 | Corollas persistent; leaf blades 2.5-3.5 mm, base auriculate. | Calluna |
| 25 | Corollas deciduous; leaf blades 3-100+ mm, base cuneate, rounded, or obtuse (not auriculate) | > 26 |
| 26 | Fruits drupaceous or baccate | > 27 |
| 26 | Fruits capsular | > 33 |
| 27 | Leaves whorled, opposite, or spirally arranged, blade ± linear (rarely narrowly elliptic to ovate or lanceolate to linear or linear-oblong or very narrowly lanceolate); fruits drupaceous | > 28 |
| 27 | Leaves alternate (rarely opposite in Xylococcus), blade narrowly elliptic, elliptic, ovate, broadly ovate, obovate, or oblanceolate; fruits baccate or drupaceous | > 29 |
| 28 | Shrubs erect, ca. 2(-5) m; leaves whorled or opposite, blade 2.5-8 cm; inflorescences terminal panicles; fruits dry, brown or reddish brown; s California. | Ornithostaphylos |
| 28 | Shrubs prostrate, 0.5-1 m; leaves whorled or spirally arranged, blade 0.2-0.7 cm; inflorescences axillary, solitary flowers; fruits fleshy, black, purple, pink, or red; Greenland, Canada, n United States. | Empetrum |
| 29 | Fruits papillate or roughened and tuberculate, ± juicy | > 30 |
| 29 | Fruits smooth, dry, mealy, or juicy | > 31 |
| 30 | Leaf blades glabrous abaxially; fruits baccate, orange-red, red, or blackish red. | Arbutus |
| 30 | Leaf blades usually densely gray-tomentose abaxially; fruits drupaceous, red. | Comarostaphylis |
| 31 | Leaf margins strongly revolute; fruits dry, pyrenes connate. | Xylococcus |
| 31 | Leaf margins plane (rarely revolute); fruits fleshy (usually mealy, sometimes juicy), pyrenes usually distinct, sometimes some or all connate | > 32 |
| 32 | Petioles winged; leaf blade margins crenate to serrulate; shrubs; stems prostrate. | Arctous |
| 32 | Petioles not winged or absent; leaf blade margins entire or serrulate (sometimes ciliate); shrubs or trees; stems prostrate to erect. | Arctostaphylos |
| 33 | Leaves whorled; corollas persistent. | Erica |
| 33 | Leaves usually alternate or opposite (if whorled, corolla sympetalous and saucer-shaped); corollas deciduous | > 34 |
| 34 | Anthers not awned; fruit dehiscence septicidal or septifragal | > 35 |
| 34 | Anthers awned or not; fruit dehiscence loculicidal | > 40 |
| 35 | Corollas with pockets holding anthers until they open. | Kalmia |
| 35 | Corollas without pockets holding anthers | > 36 |
| 36 | Leaf blade margins appearing revolute (abaxial surfaces to 1/3 visible); older twigs glabrous or puberulent, roughened peglike projections remaining after fall of leaves | Phyllodoce |
| 36 | Leaf blade margins plane to revolute (abaxial surfaces 1/3+ visible except sometimes in bud); older twigs without peglike projections | > 37 |
| 37 | Corollas cylindric-urceolate, globose, or campanulate | > 38 |
| 37 | Corollas shallowly bell- to funnel-shaped, rotate, or campanulate | > 39 |
| 38 | Stems erect, spreading, or straggling; leaves deciduous; sepals connate ca. 3/4 their lengths; stamens 8. | Menziesia |
| 38 | Stems erect or trailing; leaves persistent; sepals nearly distinct; stamens 10; (sw Oregon). | Kalmiopsis |
| 39 | Inflorescence axes ± elongate; perulae leaflike proximally, green; (sw Alaska). | Therorhodion |
| 39 | Inflorescence axes ± short; perulae scalelike, brownish. | Rhododendron |
| 40 | Plants subshrubs; stems erect to decumbent or prostrate; leaf blades 2-6 mm; inflorescences solitary flowers; corollas campanulate | > 41 |
| 40 | Plants vines, shrubs, or trees; stems erect, (sometimes arching), ascending, or spreading; leaf blades 5-100+ mm; inflorescences usually racemes, panicles, fascicles, or corymbs, sometimes solitary flowers; corollas broadly campanulate to cylindric or urceolate | > 42 |
| 41 | Leaves opposite; inflorescences axillary; flowers pendulous. | Cassiope |
| 41 | Leaves alternate; inflorescences terminal; flowers erect to horizontal or nodding. | Harrimanella |
| 42 | Inflorescences racemes of (2-)5-12-flowered corymbs or solitary flowers, borne on leafless stems; corollas broadly campanulate | Zenobia |
| 42 | Inflorescences racemes, fascicles, panicles, or umbelliform corymbs, borne on leafy stems or twigs; corollas cylindric to urceolate | > 43 |
| 43 | Inflorescences panicles on shoots of current season, terminal; corollas densely unicellular-hairy. | Oxydendrum |
| 43 | Inflorescences racemes, fascicles, panicles, or umbelliform corymbs, terminal or axillary; corollas glabrous or with various multicellular and/or unicellular hairs, never densely unicellular-hairy | > 44 |
| 44 | Leaf blades with multicellular (stalked-glandular and/or elongate and eglandular) hairs, with or without unicellular hairs | > 45 |
| 44 | Leaf blades with unicellular hairs or peltate or lepidote scales, or glabrous | > 49 |
| 45 | Capsules with pale, decidedly thickened, whitish sutures; corollas sparsely stipitate-glandular. | Lyonia |
| 45 | Capsules without thickened sutures; corollas without multicellular hairs | > 46 |
| 46 | Pith chambered; leaf blade venation reticulodromous (reticulum rather dense and with all orders ± equally prominent). | Agarista |
| 46 | Pith solid; leaf blade venation brochidodromous to reticulodromous (of varied thickness and conspicuousness) | > 47 |
| 47 | Pedicels with 2 proximal bracteoles; anthers without awns or 2-awned. | Leucothoe |
| 47 | Pedicels with distal or medial bracteoles; anthers with or without awns | > 48 |
| 48 | Leaves persistent; pedicels with 2 medial bracteoles; anthers with 2 papillose, downward-pointing spurs at anther- filament junction. | Pieris |
| 48 | Leaves deciduous; pedicels with 2 distal bracteoles; anthers with 2 or 4 ± erect awns at anther apex. | Eubotrys |
| 49 | Leaf blades linear to narrowly elliptic or oblong, without peltate scales; stamens without awns. | Andromeda |
| 49 | Leaf blades elliptic, lanceolate, oblanceolate, oblong, or obovate, with silvery, brownish, stramineous, or ferrugineous scales (sometimes also hairy) | > 50 |
| 50 | Inflorescences fascicles, axillary, developing and blooming in spring, without leaflike bracts; corollas lepidote on outside; anthers without hollow "awns"; capsules with pale, thickened sutures. | Lyonia |
| 50 | Inflorescences racemes, terminal, developing in late summer and overwintering in exposed condition, with leaflike bracts; corolla glabrous on outside; anthers apically narrowed, forming hollow "awns" (tubules); capsules without thickened sutures. | Chamaedaphne |