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The families of flowering plants

L. Watson and M.J. Dallwitz

Ericaceae Juss.

Including Arbuteae (Arbutaceae) J.G Agardh, Arctostaphyleae (Arctostaphylaceae) J.G. Agardh, Cerantheraceae Dulac, Menziesiaceae Klotzsch, Rhododendra (Rhododendraceae) Juss., Rhodoraceae Ventenat, Siphonandraceae Klotzsch, Vacciniaceae S.F. Gray; excluding Empetraceae, Epacridaceae, Monotropaceae, Pyrolaceae.

Habit and leaf form. Small trees, or shrubs (often ‘ericoid’), or lianas (a few); bearing essential oils (e.g., Gaultheria spp.), or without essential oils (usually). Plants green and photosynthesizing. Self supporting, or epiphytic (sometimes), or climbing (a few). On acid substrates, helophytic to xerophytic. Leaves persistent, or deciduous; minute to very large; alternate; spiral, or distichous, or four-ranked; ‘herbaceous’, or leathery; petiolate, or subsessile, or sessile; non-sheathing; gland-dotted (e.g., Gaultheria), or not gland-dotted; aromatic (rarely), or without marked odour; simple; epulvinate. Lamina entire; acicular, or linear, or lanceolate to ovate; one-veined, or pinnately veined, or palmately veined; cross-venulate, or without cross-venules. Leaves exstipulate. Lamina margins flat, or revolute. Vegetative buds scaly, or not scaly. Leaf development not ‘graminaceous’.

Leaf anatomy. The leaf lamina dorsiventral (mostly, usually abaxial), or bifacial, or centric. Mucilaginous epidermis present, or absent. Stomata anomocytic, or paracytic, or cyclocytic (Epigaea and Bejaria only). Hairs present (in great variety, including branched, stellate and shaggy: see illustration); eglandular and glandular; unicellular and multicellular. Unicellular hairs branched and simple. Multicellular hairs uniseriate and multiseriate. Complex hairs present, or absent; when present, peltate, or stellate, or clavate, or capitate. Adaxial hypodermis present, or absent. Lamina with secretory cavities, or without secretory cavities (usually). Secretory cavities when present, containing oil. The mesophyll containing crystals. The crystals druses and solitary-prismatic. Minor leaf veins without phloem transfer cells (5 genera).

Axial (stem, wood) anatomy. Pith homogeneous, or heterogeneous. Cork cambium present (though “not always well defined”); initially deep-seated (usually), or initially superficial (e.g. Agapetes). Nodes unilacunar (usually), or tri-lacunar. Primary vascular tissues in a cylinder, without separate bundles; collateral. Internal phloem absent. Secondary thickening developing from a conventional cambial ring (often developing very slowly). Primary medullary rays generally narrow, or mixed wide and narrow and narrow.

The wood ring porous, or semi-ring porous (commonly), or diffuse porous. The vessels typically very small; solitary (often, more or less exclusively), or radially paired, or in radial multiples, or clustered, or in tangential arcs. The vessel end-walls scalariform, or scalariform and simple, or simple. The vessels without vestured pits; with spiral thickening, or without spiral thickening. The axial xylem with tracheids, or without tracheids; without vasicentric tracheids; with fibre tracheids (commonly), or without fibre tracheids; with libriform fibres (often additional to fibre tracheids); including septate fibres (rarely), or without septate fibres. The fibres with spiral thickening, or without spiral thickening. The parenchyma more or less apotracheal (when recordable, but typically very sparse or absent). ‘Included’ phloem absent. The wood not storied. Tyloses present (seen only in Oxydendrum), or absent.

Reproductive type, pollination. Plants hermaphrodite (nearly always), or dioecious (Epigaea). Pollination (usually?) entomophilous; mechanism conspicuously specialized (occasionally - e.g. Kalmia, with explosively springing stamens), or unspecialized.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’ (usually), or solitary; in racemes, in spikes, in heads, in corymbs, and in panicles. The ultimate inflorescence units racemose. Inflorescences terminal, or axillary. Flowers bracteate; usually bracteolate (bracteoles usually 2 or 3); small to large; regular, or somewhat irregular to very irregular (Rhododendroideae). The floral irregularity (when apparent) involving the perianth and involving the androecium. Flowers (4–)5(–7) merous; cyclic; nearly always pentacyclic. Free hypanthium absent. Hypogynous disk usually present; intrastaminal.

Perianth with distinct calyx and corolla; (7–)10(–14); 2 whorled. Calyx (4–)5(–7); 1 whorled; polysepalous, or gamosepalous; cupuliform (usually), or cyathiform; fleshy (occasionally), or non-fleshy; persistent. Corolla (3–)5(–7); 1 whorled; gamopetalous (usually), or polypetalous (occasionally); imbricate, or valvate (less often); campanulate, or urceolate, or hypocrateriform, or funnel-shaped, or tubular; regular (usually), or bilabiate; white, or red, or pink, or purple; persistent, or deciduous.

Androecium 8–10 (usually), or 5 (Loiseleuria). Androecial members more or less free of the perianth (usually), or adnate (e.g., inserted high on the tube in Notopora); all equal, or markedly unequal; free of one another; 1 whorled (occasionally), or 2 whorled (usually). Androecium exclusively of fertile stamens. Stamens 5 (rarely), or 8–10; isomerous with the perianth (rarely, when the antepetalous cycle is absent), or diplostemonous (usually); alternisepalous (usually obdiplostemonous), or oppositisepalous (rarely, when the antepetalous cycle is wanting); alternating with the corolla members, or both alternating with and opposite the corolla members. Anthers dorsifixed, or basifixed; becoming inverted during development, their morphological bases ostensibly apical in the mature stamens; versatile; dehiscing via pores to dehiscing via short slits (nearly always), or dehiscing via longitudinal slits (Epigaea, Loiseleuria, Leiophyllum); finally introrse, or latrorse; bilocular; tetrasporangiate; appendaged (commonly), or unappendaged (most Rhododendroideae). The anther appendages when present apical, or dorsal. Endothecium developing fibrous thickenings, or not developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis simultaneous. Anther wall of the ‘dicot’ type, or of the ‘reduced’ type (Gaultheria). Pollen shed in aggregates (typically), or shed as single grains (e.g. Enkianthus); with viscin strands (especially Rhododendroideae), or without viscin strands; usually in tetrads. Pollen grains aperturate; 3 aperturate; colporate; not lophate; 2-celled (in 7 genera), or 3-celled (Enkianthus only).

Gynoecium (2–)4–5(–7) carpelled (7 in Bejaria). Carpels isomerous with the perianth, or reduced in number relative to the perianth. The pistil (1–)4–5(–7) celled. Gynoecium syncarpous; eu-syncarpous; superior to inferior. Ovary (1–)4–5(–7) locular (usually with the locules opposite the corolla lobes). Gynoecium stylate. Styles 1; attenuate from the ovary, or from a depression at the top of the ovary; apical. Stigmas 1; usually capitate (greatly expanded in Epigaea). Placentation axile, or apical. Ovules 1–50 per locule (i.e. to ‘many’); pendulous to ascending; epitropous in Arctostaphylos; non-arillate; anatropous, or campylotropous, or hemianatropous; unitegmic; tenuinucellate. Endothelium differentiated. Embryo-sac development Polygonum-type, or Allium-type. Polar nuclei fusing prior to fertilization, or fusing only after one has been fertilized, or fusing simultaneously with the male gamete (? — sometimes ‘only in association with a male gamete’ in Vaccinium). Antipodal cells formed; 3; proliferating (e.g. in Leucothoë), or not proliferating. Synergids pear-shaped, or hooked (often). Endosperm formation usually cellular. Endosperm haustoria present; chalazal and micropylar. Embryogeny solanad.

Fruit fleshy, or non-fleshy; dehiscent, or indehiscent; a capsule, or a berry, or a drupe, or a nut (rarely); when superior or perigynous, enclosed in the fleshy perianth (occasionally), or without fleshy investment external to the original ovary. Capsules septicidal, or loculicidal. The drupes with separable pyrenes, or with one stone (?). Dispersal unit the seed, or the fruit. Seeds copiously endospermic. Endosperm oily. Seeds minute, or small; winged (commonly), or wingless. Embryo well differentiated. Cotyledons 2. Embryo achlorophyllous (4/8); straight.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. C3. C3 physiology recorded directly in Arctostaphylos, Rhodendrodendron. Anatomy non-C4 type (widely examined by L.W.). Sugars transported as sucrose (Arbutus), or as oligosaccharides + sucrose (Rhododendron). Inulin recorded (possibly, in Calluna, Gibbs 1974). Cyanogenic (rarely), or not cyanogenic. Alkaloids present (rarely), or absent. Verbascosides not detected. Arbutin present (in many genera). Iridoids detected; ‘Route I’ type (?), or ‘Route II’ type (+decarb.). Saponins/sapogenins absent. Proanthocyanidins nearly always present; cyanidin, or cyanidin and delphinidin. Flavonols present; kaempferol, or quercetin, or kaempferol and quercetin, or quercetin and myricetin, or kaempferol, quercetin, and myricetin (and sometimes with gossypetin). Ellagic acid present (only in the 3 species of Arbutus screened), or absent (14 species, 13 genera, including Arctostaphylos). Andromedotoxin recorded. Ursolic acid present. Aluminium accumulation not found.

Geography, cytology. Frigid zone and temperate, sub-tropical to tropical (then usually at high altitude). Almost cosmopolitan, but tropical representation mostly at high altitude, and poorly represented in Australasia. X = (8–)12 or 13(–23).

Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Corniflorae; Ericales. Cronquist’s Subclass Dilleniidae; Ericales. APG III core angiosperms; core eudicot; Superorder Asteranae. APG IV Order Ericales.

Species 1350. Genera about 100; Acrostemon, Agapetes, Agarista, Andromeda, Anomalanthus, Anthopteropsis, Anthopterus, Arachnocalyx, Arbutus, Arctostaphylos, Bejaria, Bruckenthalia, Bryanthus, Calluna, Calopteryx, Cassiope, Cavendishia, Ceratostema, Chamaedaphne, Coccosperma, Coilostigma, Comarostaphylis, Costera, Craibiodendron, Daboecia, Demosthenesia, Didonica, Dimorphanthera, Diogenesia, Diplarche, Diplycosia, Disterigma, Enkianthus, Eremia, Eremiella, Erica, Findlaya, Gaultheria, Gaylussacia, Gonocalyx, Grisebachia, Harrimanella, Kalmia, Kalmiopsis, Killipiella, Lateropora, Ledothamnus, Ledum, Leiophyllum, Leucothoë, Loiseleuria, Lyonia, Macleana, Macnabia, Malea, Menziesia, Mitrastylus, Mycerinus, Nagelocarpus, Notopora, Oreanthes, Ornithostaphylos, Orthaea, Oxydendrum, Pellegrinia, Pernettya, Pernettyopsis, Phyllodoce, Pieris, Platycalyx, Plutarchia, Polyclita, Psammisia, Rhododendron, Rhodothamnus, Rusbya, Salaxis, Satyria, Scyphogyne, Semiramisia, Simocheilus, Siphonandra, Sphyrospermum, Stokoeanthus, Sympieza, Syndsmanthus, Tepuia, Thamnus, Themistoclesia, Therorhodion, Thibaudia, Thoracosperma, Tsusiophyllum, Utleya, Vaccinium, Xylococcus, Zenobia.

General remarks. Pedantic nomenclatural interpretation of cladistic theories has resulted of late in submerging Empetraceae, Epacridaceae, Monotropaceae and Pyrolaceae in the Ericaceae. Comparisons among our compiled descriptions using Intkey provide ample evidence to justify retaining the segregate ericalean families for practical purposes. For example, the exclusively southern hemisphere Epacridaceae differ from the traditional, sensu stricto version of Ericaceae almost absolutely in the tetracyclic flowers and non-versatile, bisporangiate stamens; the remarkable diversity of hair types found in abundance in Ericaceae contrasts spectacularly with the general glabrosity of Epacridaceae; particular states of 78 characters included in the present compilation (including very conspicuous vegetative, floral and pollen-morphological features) are either confined to or are very rare in one family or the other; and arbutin, andromedotoxin and inulin seem not to have been found in Epacridaceae. See Watson 1965; Watson, Williams and Lance 1967; Stevens 1971.

Economic uses, etc. Edible berries from Arctostaphylos, Gaylussacia, Vaccinium etc. (bearberry, bilberry, blueberry, whortleberry, buckleberry, cranberry etc). Many species and genera are cultivated as ornamentals (e.g. Erica, Rhododendron, Arbutus, Pieris). ‘Briar’ pipes are made from Erica spp.


How oft, though moss and grass are seen,
Tann’d bright for want of flowers,
Still keeps the Ling its darksome green,
Thickset with little flowers
(John Clare, quoted by Ann Pratt, ‘Wild Flowers’ (1857) - Calluna)

There pinch the maids as blue as bilberry:
Our radiant queen hates sluts and sluttery
(‘Merry Wives’, v., 5 - Vaccinium myrtillus)

. . . blocks of granite
Rise in beauty all around,
Lichen grown, and moss enamelled,
Ivy wreathed, and bilberry crowned.
(George Heath, ‘Rudyard’, c. 1865)

Rhodora! if the sages ask thee why
This charm is wasted on the earth and sky,
Tell them, dear, that if eyes were made for seeing,
Then beauty is its own excuse for being
(R.W. Emerson, ‘The Rhodora’ - ‘Rhodora’ = Rhododendron)

Illustrations. • Le Maout and Decaisne: Erica cinerea. • Le Maout and Decaisne: Rhododendron. • Le Maout and Decaisne: Vaccinium. • ‘Vaccinium serpens’ Wight (cf. Agapetes) and Agapetes salignum (as Vaccinium): Hooker’s Illustrations of Himalayan plants (1855). • Agapetes incurvata, as Pentapterygium rugosum: Bot. Mag. 86 (1860). • Andromeda polifolia: Eng. Bot. 883 (1866). • Arbutus menziesii: as A. procera, Bot. Reg. 1753, 1836. • Arbutus unedo (B. Ent., 1836). • Arbutus unedo: Eng. Bot. 882 (1866). • Arbutus xalapensis: Bot. Reg. 1839, 67. • Arctostaphylos alpinus (as A. alpina): Eng. Bot. 880 (1866). • Arctostaphylos pungens: Bot. Reg. 1844, 17. • Arctostaphylos tomentosa: Bot. Reg. 1791, 1836. • Arctostaphylos uva-ursae (B. Ent., 1835). • Artostaphylos uva-ursi: Eng. Bot. 881 (1866). • Cavendishia bracteata (as Thibaudia): Hook. Ic. Pl. 2 (1837). • Cavendishia bracteata, as Thibaudia acuminata: Bot. Mag. 95 (1869). • Calluna vulgaris (B. Ent., 1826). • Ceratostema longiflorum: Lemaire, Ilustr. Horticole (1854). • Comarostaphylis discolor: Hook. Ic. Pl. 1 (1837). • Comarostaphylis arbutoides: Bot. Reg. 29 (30), 1843. • Daboecia cantabrica (B. Ent.). • Daboecia cantabrica (as Menziesia polifolia): Eng. Bot. 885 (1866). • Diplycosia ciliata: Hook. Ic. Pl. 9 (1852). • Enkianthus japonicus (cf. E. perulatus): Bot. Mag. 96 (1870). • Erica chloroloma: Bot. Reg. XXIV, 17 (1838). • Erica cinerea (B. Ent., 1824). • Erica tetralix (B. Ent., 1824). • Gaultheria antarctica: Hooker, Fl. Antarctica (1844). • Gaultheria tasmanica (as Pernettya) and G. depressa (as G. antipoda): Hooker, Fl. Tasmaniae (1860). • Gaultheria lanceolata: Hooker, Fl. Tasmaniae (1860). • Gaultheria rupestris: Hooker, Fl. Novae-Zelandiae (1853). • Gaultheria oppositifolia: Hooker, Fl. Novae-Zelandiae (1853). • Gaultheria shallon: Bot. Reg. 1411, 1831. • Gaultheria phillyreifolia: as Andromeda phyllireaefolia, Bot. Reg. 1844, 36. • Gaultheria tomentosa: Hook. Ic. Pl. 4 (1841). • Gaylussacia pseudovaccinium: Bot. Reg. 1844, 62. • Loiseleuria procumbens: Eng. Bot. 884 (1866). • Macleania floribunda: Hook. Ic. Pl. 2 (1837). • Macleania longiflora: Bot. Reg. 1844, 25. • Notopora schlombergkii: Hook. Ic. Pl. 12 (1876). • Pernettya mucronata: Bot. Reg. 1675, 1835. • Pernettya mucronata var. angustifolia: Bot. Reg. xxvi, 63 (1840). • Philippia chamissonis: Thonner. • Phyllodoce caerulea (as Menziesia aerulea): Eng. Bot. 886 (1866). • Psammisia longicola: Bot. Mag. 91 (1865). • Rhododendron ericoides: Hook. Ic. Pl. 9 (1852). • Rhododendron molle subsp. japonicum: Bot. Reg. 1253, 1829. • Rhododendron verticillatum: Hook. Ic. Pl. 9 (1852). • Vaccinium madagascariensis, as V. emirnense: Hook. Ic. Pl. 2 (1837). • Vaccinium borneense, as Rigiolepis: Hook. Ic. Pl. 12 (1876). • Vaccinium myrtillus: B. Ent. 73. • Vacciniium oxycoccus: B. Ent. 523, 1834. • Vaccinium oxycoccus: Eng. Bot. 876 (1866). • Vaccinium uliginosum: Eng. Bot. 878 (1866). • Vaccinium vitis-idaea: B. Ent. 662. • Vaccinium vitis-idaea: Eng. Bot. 877 (1866). • Assorted genera of Ericaceae: leaf hairs (Solereder, 1908).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 15th April 2018.’.