Including Empetraceae, Monotropaceae, and Pyrolaceae of Michigan Flora.
1. Leaves reduced to non-green scales; plants entirely white, yellow, reddish, orange, or maroon.
2. Corolla of partly united petals, 5–7 mm long; calyx of 5 normal sepals, regular; plant ± densely glandular-pubescent, clammy; inflorescence (axis) erect from the beginning.
2. Corolla of separate petals, 8–19 mm long; calyx of 0–4 bract-like sepals, irregular; plant glabrous or ± finely pubescent (not glandular); inflorescence bent or nodding when young (becoming erect).
3. Flowers few to many; plant ± pubescent, at least in inflorescence, yellowish to ± orange or even reddish when fresh, becoming at most a dark brown long after flowering.
3. Flower solitary; plant glabrous (except for petals and filaments), pure white when fresh (rarely pinkish), soon turning black (except for anthers) when bruised, old, or dry.
1. Leaves green (these sometimes small and needle- or scale-like); plants green (except for older bark in woody species).
4. Leaves scale-like or needle-like, less than 1.5 mm wide.
5. Leaves ± needle-like, tapered at the base; fruit a black berry.
5. Leaves ± scale-like, broader and auriculate at base; fruit a capsule.
4. Leaves with expanded flat blades, more than 1.5 mm wide.
6. Leaves in a basal rosette; plants herbaceous.
7. Style ± strongly bent downward, at least 4 mm long; inflorescence a ± symmetrical raceme.
Pyrola (in part)
7. Style straight, short or long; inflorescence various (usually 1-flowered or a 1-sided raceme).
8. Inflorescence 1-flowered, the corolla 15–20 (–22) mm broad, flat (petals widely spreading); anthers prolonged into a short cylindrical tube below the pore; valves of capsule glabrous; style (not including prominent stigma lobes) 3–5 mm long.
8. Inflorescence racemose, the corolla 3–7 mm broad, ± bell-shaped (petals close about reproductive parts); anthers not prolonged into tubes; valves of capsule with cobwebby fibers on the margins when dehiscing; style various (but stigma only very shallowly lobed).
9. Raceme 1-sided; style 2.5–6 (–6.5) mm long, protruding at maturity from the corolla; sepal margins finely toothed or erose.
9. Raceme symmetrical; style ca. 1.5 mm or less long, scarcely if at all protruding beyond the corolla; sepal margins entire.
6. Leaves opposite, alternate, or whorled; plants woody (sometimes small subshrubs woody only at the base or prostrate creepers).
10. Leaves opposite or whorled; flowers 8–20 mm broad.
11. Leaves coarsely few-toothed; subshrub woody only at base, forming colonies by rhizomes.
11. Leaves entire; true woody, clump forming shrub.
10. Leaves all alternate; flowers in most species less than 8 mm broad.
12. Leaf blades with very densely pubescent lower surfaces (tomentose or minutely puberulent), mostly 2.5–15 (–20) times as long as broad, the margins strongly revolute.
13. Flowers with urn-shaped pink (rarely white) corolla and conspicuous calyx (± 1.5–2.5 mm long); leaves very minutely but densely white- (rarely grayish-) puberulent beneath.
13. Flowers with spreading, separate, white petals and minute calyx (not over 0.5 mm); leaves densely tomentose beneath with brownish or white woolly hairs.
12. Leaf blades glabrous to somewhat pubescent beneath (if ± densely pubescent, the hairs straight and leaf margins flat), less than 3 (rarely 4) times as long as broad, usually with flat margins.
14. Leaf blades (evergreen) with scurfy appearance (especially beneath) from round orange-brown (to whitish) scales, otherwise glabrous; fruit a dry capsule; flowers white, subtended by reduced leaves in a ± elongate raceme-like inflorescence; plant a bushy-branched shrub.
14. Leaf blades without scurfy scales (if leaves resin-dotted, then deciduous and ± pubescent); fruit ± fleshy (at least within); flowers and habit various.
15. Plant an upright, bushy-branched, stiff-stemmed shrub; leaves deciduous; ovary inferior; fruit a blue or black berry.
16. Leaves with shiny orange resinous dots (especially beneath), entire, usually ± pubescent beneath (at least on midrib); fruit containing 10 hard nutlets.
16. Leaves without resinous dots, entire to finely toothed, glabrous to pubescent; fruit containing many fine seeds.
Vaccinium (in part, couplet 4)
15. Plant with primary stems lax, creeping or prostrate (sometimes with short erect shoots, and in Gaultheria procumbens the primary stem a shallow or surficial rhizome with erect usually unbranched shoots); leaves evergreen; ovary inferior or superior; fruit red or white, berry-like (except in Epigaea).
17. Larger leaf blades (3.5–) 4–7.5 (–9) cm long, cordate or subcordate at base, on distinct petioles at least a fourth as long; corolla with nearly parallel-sided tube and flaring lobes; anthers opening by longitudinal slits (plants functionally dioecious); fruit a nearly spherical capsule filled with fleshy white placental material and subtended by both sepals and bracts.
17. Larger leaf blades less than 4.5 (–5) cm long, rounded or tapered to petioles less than a fourth as long; corolla urn-shaped or cleft to the base with reflexed petals; anthers opening by terminal pores (flowers mostly bisexual); fruit fleshy throughout, subtended by sepals (or bracts) or (in most species) the ovary inferior and the fruit incorporating the calyx.
18. Leaf blades with scattered dark elongate glands or bristles beneath; flowers 4-merous.
19. Leaves rounded or even minutely notched (though with a gland) at apex; berries in terminal clusters, red; stems short-puberulent with incurved hairs or glabrous; very rare (only from Isle Royale), without wintergreen odor.
19. Leaves abruptly acute at gland-tipped apex; berries solitary in axils, white; stems with coarse appressed bristly hairs; common, with wintergreen flavor and odor.
18. Leaf blades without bristles or glands beneath; flowers 4-merous or 5-merous.
20. Corolla 4-merous, cleft to the base, the petals strongly reflexed; leaf blades whitened beneath, less than 1.2 (–1.4) cm long; calyx not fleshy in the mature fruit, but ovary inferior.
Vaccinium (in part, couplet 3)
20. Corolla 5-merous, sympetalous, urn-shaped; leaf blades pale or dark green but not whitened beneath, mostly 1–4.5 (–5) cm long; calyx fleshy and incorporated in the mature fruit or the ovary clearly superior.
21. Plant with wintergreen odor and flavor; leaf margins with obscure, remote teeth (bearing rusty brown bristles when young); leaves borne only at summit of erect shoots from surficial or shallow rhizome; flowers July–August.
21. Plant without wintergreen odor or flavor; leaf margins strictly entire; leaves all along branches and shoots; flowers May (–early June).