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]

                                                                 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 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]