1 Plant an herb, subshrub, or sprawling shrub, not clonal by underground rhizomes (except Gaultheria procumbens and Epigaea repens), rarely > 3 dm tall; plants mycotrophic or hemi-mycotrophic (except Epigaea, Gaultheria, and Arctostaphylos).

  2 Plants without chlorophyll (fully mycotrophic); stems fleshy; leaves represented by bract-like scales, white or variously colored, but not green; pollen grains single; [subfamily Monotropoideae; tribe Monotropeae].

    3 Petals united; fruit nodding, a berry; flower and fruit several per stem

    3 Petals separate; fruit erect, a capsule; flower and fruit 1-several per stem.

      4 Flowers few to many, racemose; stem pubescent, at least in the inflorescence; plant yellow, orange, or red when fresh, aging or drying dark brown

      4 Flower solitary; stem glabrous; plant white (rarely pink) when fresh, aging or drying black

  2 Plants with chlorophyll (hemi-mycotrophic or autotrophic); stems woody; leaves present and well-developed, green; pollen grains in tetrads (single in Orthilia).

        5 Herb with a rosette of ascending basal leaves; flowers scapose; [subfamily Monotropoideae; tribe Pyroleae].

          6 Style and filaments straight; filaments straight, the anthers closely surrounding the style; inflorescence distinctly secund (1-sided)

          6 Style and filaments strongly declined; filaments curved, the anthers not closely surrounding the style; inflorescence slightly or not at all secund (1-sided)

        5 Subshrub or sprawling shrub with cauline leaves; flowers axillary (except scapose in Chimaphila).

             7 Plant erect, the leaves clustered near the apex of the single stem.

               8 Leaves lanceolate or oblanceolate, normally 2-4× as long as wide (sometimes proportionately less narrow in stunted individuals; fruit a capsule, borne 1-several on an erect scape above the leaves [subfamily Monotropoideae; tribe Pyroleae]

               8 Leaves obovate, 1-2× as long as wide; fruit a red berry, borne on nodding axillary pedicels beneath the leaves; [subfamily Vaccinioideae; tribe Gaultherieae]

             7 Plant creeping or sprawling, leaves scattered along the stems.

                 9 Flowers solitary and axillary; fruit a white berry; [subfamily Vaccinioideae; tribe Gaultherieae]

                 9 Flowers in axillary or terminal spikes or racemes; fruit a fleshy loculicidal capsule or red drupe.

                   10 Leaves glabrous, 1-3 cm long, tapered to the base; corolla urceolate; calyx not subtended by large bracts; [subfamily Arbutoideae]

                   10 Leaves pilose (glabrate in age), 2-10 cm long, rounded or subcordate at the base; corolla salverform, the lobes spreading; calyx subtended by 2 large bracts; [subfamily Ericoideae; tribe Phyllodoceae]

1 Plant either a shrub or tree (> 3 dm tall), or a shrub 1-3 dm tall (rarely a woody needle-leaved subshrub 0.5-1 m and definitely and obviously clonal by underground rhizomes; plants not mycotrophic or hemi-mycotrophic.

                     11 Leaves ca. 1 mm wide, 3-12 mm long, appearing opposite, alternate, or whorled (the internodes very short, thus the leaves generally appearing whorled); petals absent; fruit a subglobose, 2-stoned drupe, 1-3 mm in diameter; branches often appearing in whorls of 3-7; [subfamily Ericoideae; tribe Empetreae]

                       12 Leaves 5-15 mm long; shrubs 5-25 dm tall; drupes yellow or reddish, 1.5-3 mm in diameter; [of SC southward]

                       12 Leaves 3-6 mm long; shrubs 1.5-6 dm tall; drupes gray, 1-1.5 mm in diameter; [of NJ northward]

                     11 Leaves either > 2 mm wide or < 5 mm long, mostly alternate or whorled; petals present; fruit not as above, mostly either a capsule or 10- or many-seeded berry; branches appearing alternate or whorled; [subfamily Vaccinioideae; tribe Vaccinieae].

                          13 Ovary inferior; fruit indehiscent, a fleshy berry; [blueberries and huckleberries].

                            14 Ovary 10 locular; seeds 10; leaves glandular-punctate, at least on the lower surface (except G. brachycera)

                            14 Ovary 4-5 locular; seeds numerous; leaves not glandular-punctate

                          13 Ovary superior; fruit dehiscent, a dry capsule; [other heaths].

                              15 Petals separate; fruit 2-7-locular; either a shrub to 1 m tall with ovate to oblong, evergreen leaves, 0.6-1.2 cm long, or a shrub to small tree 2-6 (-9) m tall with elliptic, deciduous leaves, 4-12 cm long, or a shrub 1-2.5 m tall, with elliptic to ovate, evergreen leaves 2-4 cm long; [subfamily Ericoideae; tribe Phyllodoceae]. {add Rhododendron groenlandicum}

                                16 Fruit 2-3 (5)-locular; shrub to 1 m tall; leaves, 0.4-1.2 cm long; petals 2-4 mm long

                                16 Fruit 4-7-locular; shrub to small tree 1-6 (-9) m tall; leaves 2-12 cm long; petals 12-30 mm long.

                                  17 Fruit 7-locular; leaves evergreen 2-4 cm long; petals 20-30 mm long; shrub 1-2.5 m tall

                                  17 Fruit 4-5-locular; leaves deciduous, 4-12 cm long; petals 12-14 mm long; shrub to small tree 2-6 (-9) m tall

                              15 Petals fused for part or all their lengths; fruit (4-) 5-locular; shrub or tree with leaves of various shape, evergreen or deciduous, these either < 6 mm long, linear and whorled, or > 12 mm long.

                                    18 Leaves opposite or whorled, < 5 mm long, linear; [subfamily Ericoideae, tribe Ericeae]

                                       19 Leaves opposite, sessile, clasping at the base

                                       19 Leaves whorled (in 4s), petiolate

                                    18 Leaves alternate or whorled, > 20 mm long.

                                         20 Flowers 4-merous; fruits 4-locular; leaves with a series of fascicles of trichomes on the midrib below; [subfamily Ericoideae; tribe Rhodoreae]

                                         20 Flowers 5-merous; fruits 5-locular; leaves not as above.

                                           21 Leaves coriaceous, evergreen, shiny and dark green above.

                                             22 Leaves sharply and distinctly serrate.

                                               23 Pedicels slender, 7-10 mm long; filaments strongly curved just below the anthers; pith transversely diaphragmed; [subfamily Vaccinioideae; tribe Lyonieae]

                                               23 Pedicels stout, 2-6 mm long; filaments straight; pith solid; [subfamily Vaccinioideae; tribe Gaultherieae]

                                             22 Leaves entire, or obscurely and finely crenulate-serrulate.

                                                 24 Capsules elongate, > 2× as long as broad, 8-18 mm long; [subfamily Ericoideae; tribe Rhodoreae]

                                                 24 Capsules ovoid to globose or subglobose, about as long as broad, 5-8 mm long.

                                                    25 Leaves with a prominent vein running parallel to (and about 1 mm in from) the margin; [subfamily Vaccinioideae; tribe Lyonieae]

                                                    25 Leaves without a prominent marginal vein.

                                                      26 Corolla saucer-shaped, 10-30 mm across; leaves entire; [subfamily Ericoideae; tribe Phyllodoceae]

                                                      26 Corolla narrowly urceolate, 4-6 mm across; leaves finely crenulate-serrulate; [subfamily Vaccinioideae; tribe Lyonieae]

                                                        27 Flower stalks with 2 opposite or subopposite subulate bractlets a little below the calyx; leaves glabrous below or short-pubescent on the midvein

                                                        27 Flower stalks with 2 opposite or subopposite triangular bractlets near the base of the pedicel; leaf lower surface punctate with stalked red glands

                                           21 Leaves membranaceous or subcoriaceous, deciduous or evergreen, if subcoriaceous and evergreen, then not shiny and dark green above.

                                                          28 Capsules elongate, > 2× as long as broad, 7-23 mm long; [subfamily Ericoideae; tribe Rhodoreae]

                                                          28 Capsules ovoid to globose or subglobose, about as long as broad, or broader than long, 2-7 mm long.

                                                            29 Leaves (at least the larger) > 2.5 cm wide.

                                                              30 Pedicels with 2 bracteoles.

                                                                 31 Capsule broader than long; shrub; bracteoles just below the calyx; [subfamily Vaccinioideae; tribe Gaultherieae]

                                                              30 Pedicels without bracteoles.

                                                                   32 Leaves entire to minutely serrulate; capsule sutures pale and thickened; [subfamily Vaccinioideae; tribe Lyonieae]

                                                                   32 Leaves crenate; capsule sutures not thickened and pale; [subfamily Vaccinioideae; tribe Andromedeae]

                                                            29 Leaves < 2.5 cm wide.

                                                                     33 Leaves linear to narrowly lanceolate, 8× or more as long as wide. strongly revolute, strongly whitened beneath; [subfamily Vaccinioideae; tribe Andromedeae]

                                                                     33 Leaves broader, not revolute or slightly so, not strongly whitened below.

                                                                       34 Leaves whorled or alternate; corolla saucer-shaped, 10-20 mm across; [subfamily Ericoideae; tribe Phyllodoceae]

                                                                       34 Leaves alternate; corolla narrowly urceolate, 2-8 mm across.

                                                                         35 Pedicels with 2 bracteoles near the summit; [subfamily Vaccinioideae; tribe Gaultherieae]

                                                                         35 Pedicels with 2 bracteoles near the base; [subfamily Vaccinioideae; tribe Lyonieae]

1 Leaves evergreen.

  2 Petiole flanged or winged, constricted at the base of the blade; fruit a hesperidium

  2 Petiole linear (not flanged or winged with leafy tissue); fruit various. {add to 2b: [Sapium] EUPHORBIACEAE, [Photinia] ROSACEAE, [Prunus (caroliniana)] ROSACEAE, [Ilex (cassine, myrtifolia)] AQUIFOLIACEAE}

    3 Leaves 7-20 cm long, usually at least some on a branch > 12 cm long, thick in texture but readily flexible when fresh.

      4 Inflorescence of a solitary flower, axillary, 5-7 cm across; fruit a capsule, ca. 1 cm in diameter

      4 Incflorescence a corymb of many, smaller flowers; fruit a pome, 0.4-0.8 (-1.2) cm in diameter

    3 Leaves 3-12 cm long, thick in texture and also noticeably stiff.

        5 Leaf with a spinose margin, the marginal spines well-developed, generally arrayed along most of the leaf margin and borne at nearly a right angle to the midvein

        5 Leaf margins serrate with one or a few stiff teeth (sometimes sharpish, but not spines), these usually towards the apex of the leaf and oriented towards the leaf apex

1 Leaves deciduous.

          6 Secondary veins neatly pinnate, the veins on each side of the midrib evenly spaced, parallel to one another, and extending nearly or actually to the leaf margin; fruit either a 1-seeded nut (dry, with or without samaroid wings, bracts, a subtending cupule, or an enclosing and valvate involucre) or a fleshy drupe with 2-4 stones.

             7 Leaves doubly-serrate, the number of teeth greater than the number of the pinnate secondary veins (sometimes obscurely so in Planera in ULMACEAE); fruit a nut or samaroid nut, lacking a cupule or valvate involucre, though sometimes associated with green, leaf-like bracts.

               8 Flowers unisexual, in catkins, the tree monoecious; leaf base symmetrical

               8 Flowers bisexual, in axillary fascicles, the tree androgynous; leaf base strongly asymmetrical (oblique) or nearly or quite symmetrical.

             7 Leaves singly serrate or crenate, the teeth the same number as the secondary veins; fruit either a fleshy drupe with 2-4 stones, or a nut with a cupule (acorn) or enclosed by a valvate involucre that splits at maturity.

                 9 Fruit a fleshy drupe with 2-4 stones

                 9 Fruit dry, single-seeded (or with 1-4 nuts in Castanea).

                   10 Fruit > 9 mm long or wide, either a nut with a cupule (acorn) or 1-4 nuts enclosed by a valvate involucre that splits at maturity

                   10 Fruit < 9 mm long and wide, leathery, indehiscent, winged or not

          6 Secondary veins not as above, usually arching and/or branching or reticulating well before reaching the leaf margin; fruit various.

                     11 Leaves strongly 3-5-veined from the base; leaf blade cordate or truncate, often oblique.

                       12 Inflorescence terminal, a compound cyme; peduncles and pedicels becoming swollen, fleshy, and juicy at maturity; [plant rarely naturalized]

                       12 Inflorescence axillary, a solitary flower, a fascicle or cluster, or a cyme; peduncles and pedicels remaining stalk-like; [collectively widespread and common].

                          13 Flowers unisexual, plants monoecious; pith of mature twigs chambered with hollow sections between soft partitions

                          13 Flowers bisexual; plants hermaphroditic; pith of mature twigs continuous without hollow sections between partitions.

                            14 Flowers bisexual; inflorescence an axillary cyme; fresh leaves and stems lacking white latex; fruit simple, a 1-seeded nut; main leaf veins splitting several times towards the leaf margin and leading into the teeth without rejoining and forming a marginal vein; basal veins 5, palmate, all joining together at the summit of the petiole; main lateral leaf veins (above the basal veins) often opposite; winter buds with 3 entire bud scales (1 much smaller than the other 2)

                            14 Flowers unisexual, the pistillate inflorescence a head, the staminate inflorescence a catkin, borne on the same tree (monoecious) or on separate trees (dioecious); fresh leaves and stems with white latex; fruit a multiple of fleshy achenes; main leaf veins splitting towards the margin but then rejoining to form a prominent, looping (scalloped) marginal vein; basal veins 3, palmate, sometimes an additional prominent vein on each side joining the lateral vein above its divergence from the petiole end; main lateral leaf veins (above the basal veins) mainly alternate; winter buds with 5 ciliate-margined bud scales

                     11 Leaves pinnately veined; leaf blade base cordate, subcordate, truncate, rounded, or cuneate base, not oblique.

                              15 Inflorescence various, either with < 30 flowers or if with > 50 flowers a catkin (with a single axis); corolla with separate petals (or petals absent); fruit various, fleshy or dry, if a 5-valved capsule (Franklinia in THEACEAE), then 15-20 mm in diameter; fresh leaves without a sour taste.

                                16 Pubescence stellate (look especially in vein axils on the undersurface of the leaf)

                                16 Pubescence simple (or absent).

                                  17 Flowers very large and showy, 7-9 cm across; fruit a subglobose capsule 1.5-2 cm in diameter

                                  17 Flowers less than 2 cm across; fruit either fleshy and indehiscent, a drupe, samara, or pome, or dry and dehiscent, an ovoid or lanceolate capsule < 0.7 cm in diameter.

                                    18 Flowers unisexual, borne either in axillary catkins; trees dioecious; fruit either dehiscent, a lanceoloid or ovoid capsule (SALICACEAE) or indehiscent, a samara (Eucommia ulmoides).

                                       19 Plants bearing latex; fruit a samara, 25-32 mm long, the apex emarginate

                                       19 Plants not bearing latex; fruit a lanceoloid or ovoid capsule

                                    18 flowers bisexual (unisexual in Ilex in AQUIFOLIACEAE), borne variously in terminal or axillary clusters, cymes, racemes, or umbels, but not at all catkin-like; trees hermaphroditic (dioecious in AQUIFOLIACEAE); fruit indehiscent, a fleshy drupe or pome with 1-many seeds.

                                         20 Pith of twigs with transverse diaphragms and also continuous between the diaphragms (make a longitudinal section of twig and use at least 10× magnification; look for translucent diaphragms spaced at < 1 mm apart, with whiter pith tissue between them); fruit distinctly longer than broad, a 1-seeded drupe

                                         20 Pith of twigs lacking diaphragms, continuous and homogeneous; fruit either suborbicular to spherical or pear-shaped, either a several- to many-seeded pome, or a berry-like drupe with 4-8 seeds, or a 1-seeded drupe.

                                           21 Vascular bundle scars 1 in each leaf scar; fruit a berrylike drupe with 4-8 bony pyrenes; ovary superior, the calyx persistent at the base of the fruit

                                           21 Vascular bundle scars (2-) 3 in each leaf scar; fruit a pome or 1-seeded drupe; ovary either inferior and the calyx persistent at the summit of the fruit (Amelanchier, Crataegus, Malus, Pyrus) or superior and the calyx not at all persistent at the base of the fruit (Prunus)