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 or orange-yellow) 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)

                          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]

                                                                 31 Capsule longer than broad; tree; bracteoles generally near the middle of the pedicel; [subfamily Vaccinioideae; tribe Oxydendreae]

                                                              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 Subshrubs or dwarf shrubs, aboveground stems creeping or erect, < 15 cm tall; leaves evergreen.

  2 Leaves 1.5-3 cm wide, coarsely toothed; flowers lacking sepals and petals; [exotic species, sparingly naturalized or spreading in suburban situations]

  2 Leaves < 1.5 cm wide, finely toothed or entire; flowers with sepals and petals; [native species, collectively widespread and common].

    3 Leaves fleshy, terete in ×-section; petals 5, bright pink

    3 Leaves flat, not fleshy; petals white or pale pink.

      4 Leaves < 2.5 mm wide; corolla with petals distinct; plant creeping

      4 Leaves > 5 mm wide; corolla with petals fused (distinct in Chimaphila); plant creeping or erect

1 Shrubs, aboveground stems erect, > 30 cm tall; leaves evergreen or deciduous.

        5 Inflorescence an involucrate (composite) head subtended by phyllaries, the heads solitary or many and variously arrayed in secondary inflorescences, the ovary inferior, the corolla connate and tubular at least basally, the calyx absent, the stamens 5, the fruit a cypsela

        5 Inflorescence, flower, and fruit structure various, but not with the combination of features as above.

          6 Leaves evergreen. {add to 6a Ardisia in PRIMULACEAE, Rhaphiolepis in ROSACEAE, Camellia in THEACEAE, Ochna in OCHNACEAE}

             7 Leaves glandular-punctate on one or both surfaces with golden-yellow glands; flowers unisexual, lacking a perianth (arranged in axillary catkins); fruit a pale gray, waxy drupe with a single seed

             7 Leaves not glandular punctate; flowers bisexual or unisexual, with a white, pink, or yellow perianth; fruit various: a red, blue, or black drupe, a berry with several seeds, or a capsule.

               8 Petals connate, flowers urceolate (ERICACEAE) or rotate, white to pale pink; flowers bisexual; fruit a drupe (Ehretia in EHRETIACEAE), OR a capsule or berry (ERICACEAE)

                 9 Flowers rotate, fragrant, the petals white, arranged primarily in terminal cymes; fruit an orange or yellow drupe, each bearing 2 hemispheric nutlets (these each also composed of 2 seeds, thus the fruit bearing 4 seeds)

                 9 Flowers urceolate, fragrant or not, the petals white to pale pink, variously arranged in terminal or axillary inflorescences (occasionally solitary in axils); fruit either a capsule or a red, blue, or black berry

               8 Petals distinct, yellow or white; flowers unisexual or bisexual; fruit either a black or red drupe with several pyrenes, a red berry with several seeds, or red or black pomes.

                   10 Plants with nodal, simple or tripartite thorns; flowers bisexual, with a yellow perianth; fruit a red berry with several seeds

                   10 Plants lacking thorns; flowers unisexual or bisexual, with a white perianth (yellow or red in Ochna); fruit either a black or red drupe with several pyrenes or a red or black pome.

                     11 Petals yellow, clawed; sepals red and forming a persistent red receptacle (torus) bearing numerous blackened drupes.

                     11 Petals white, not clawed; sepals not bright red nor persistent, the fruit a drupe or pome.

                       12 Flowers unisexual; fruit a black or red drupe with several pyrenes

                       12 Flowers bisexual; fruit a red or black pome

          6 Leaves deciduous {add [Fagaceae]}.

                          13 Plants with nodal, simple or tripartite thorns; leaf teeth spinulose

                          13 Plants lacking thorns; leaf teeth acute, blunt, rounded, or callus-tipped, but not spinulose.

                            14 Leaf blade bases conspicuously oblique-cordate or angled-truncate.

                              15 Leaves crenate-wavy, with 1-2 teeth per cm of leaf margin; pubescence of leaves and stems stellate

                              15 Leaves crenate or serrate, but usually not wavy, pubescence of leaves and stems simple {add to key; verify}

                            14 Leaves crenulate, serrate or serrulate, with >2 teeth per cm of leaf margin; leaves cuneate, rounded, or subcordate at base, not oblique; pubescence of leaves and stems absent or simple.

                                16 Leaves prominently 3-veined from the base.

                                  17 Ovary 5-locular; stamens many or 5, fused or separate; fruit a 5-valved capsule or of 5 mericarps; flowers yellow or pink, or white with a pink blaze

                                  17 Ovary 3-locular; stamens 5, separate; fruit a 3-valved capsule or drupe; flowers white or pale green

                                16 Leaves pinnately veined.

                                    18 Flowers in catkins; perianth absent or very small; fruit a 1-seeded nut, samara, or waxy drupe (capsule in Salix in SALICACEAE).

                                       19 Leaves > 4 cm wide, lacking punctate glands; fruit a 1-seeded nut or samara

                                       19 Leaves < 3 cm wide, either punctate-glandular on one or both surfaces or lacking punctate glands; fruit a 1-seeded waxy drupe or a capsule.

                                         20 Leaves punctate-glandular on one or both surfaces; fruit a 1-seeded waxy drupe.

                                         20 Leaves lacking punctate glands; fruit a capsule.

                                    18 Flowers arrayed variously, but not in catkins; perianth present, conspicuous; fruit a 1-many-seeded capsule, pome, berry, or follicle.

                                           21 Ovary inferior; fruit fleshy and indehiscent, a berry or pome.

                                             22 Fruit a pome; leaves usually prominently stipular

                                           21 Ovary superior; fruit either dry and dehiscent, a capsule or an aggregate of follicles or achenes, or fleshy and indehiscent, a drupe with 4-8 pyrenes.

                                               23 Flower apocarpous; fruit an aggregate of follicles or achenes

                                               23 Flower syncarpous; fruit either a capsule or a fleshy drupe.

                                                 24 Ovary 1-carpellate; fruit a 1-seeded drupe

                                                 24 Ovary 2-8-carpellate; fruit either a capsule or a drupe with 4-8 pyrenes

                                                    25 Ovary 2-8-locular; fruit fleshy and indehiscent, a drupe with 2-8 pyrenes; flowers mostly functionally unisexual (or sometimes bisexual in RHAMNACEAE).

                                                      26 Petals connate at the base; stamens alternate to the petals and opposite to the sepals; fruit 4-8-locular, with 4-8 pyrenes

                                                      26 Petals separate (or absent in Rhamnus alnifolia); stamens opposite to the petals (when present) and alternate to the sepals; fruit 2-4-locular, with 2-4 pyrenes

                                                    25 Ovary 2-3- or 5-locular; fruit dry and dehiscent, a capsule; flowers bisexual (except Stillingia in EUPHORBIACEAE).

                                                        27 Ovary and capsule 5-locular; stamens 10-many.

                                                          28 Stamens 10; corolla urceolate, sympetalous

                                                          28 Stamens many; corolla spreading, apopetalous

                                                        27 Ovary and capsule 2-3-locular; stamens 2, 5, or 10.

                                                            29 Leaves > 5× as long as wide; stamens 2; ovary and capsule 3-locular; [plants of the Coastal Plain of SC, GA, AL, and FL]

                                                            29 Leaves < 3× as long as wide; stamens 5 or 10; ovary and capsule 2-3-locular; [plants collectively widespread].

                                                              30 Stamens 5; ovary and capsule 2-locular; leaves elliptic (widest near the middle), the teeth fine (usually > 5 points per cm of margin), and along much of the margin; inflorescence a terminal raceme; hairs of the lower leaf surface simple, erect

                                                              30 Stamens 10; ovary and capsule 3-locular; leaves obovate (widest towards the apex), the teeth obscure to coarse (usually < 4 points per cm of margin), and primarily in the upper half of the leaf; inflorescence a terminal or axillary raceme or cyme; hairs of the lower leaf surface either simple and appressed, or stellate.

                                                                 31 Leaf margins regularly and evenly serrate in the upper half of the leaf (usually nearly entire towards the base); inflorescence an elongate, many flowered (>30) raceme borne at the end of branchlets of the season; corolla of separate petals, the stamens separate; hairs of the lower leaf surface simple and appressed

                                                                 31 Leaf margins wavy or irregularly dentate, mainly in the upper half of the leaf; inflorescence a few flowered (<20) axillary raceme, cyme, or cluster; corolla fused basally into a tube, the stamens adnate to the tube; hairs of the lower leaf surface stellate