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 berry; leaves lacking stipules

                                             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 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

1 Ovary inferior; fruit indehiscent (pome).

  2 Inflorescence a panicle, of > 25 flowers (6-40 in Pyracantha); leaves leathery, evergreen.

    3 Plants armed with thorns

    3 Plants unarmed.

      4 Pomes purplish-black, 7-10 mm in diameter, each with 3-5 seeds; leaves mostly 10-30 cm long

      4 Pomes orangey yellow, (10-) 20-30 mm in diameter, each with 1-2 seeds; leaves (2-) 4-10 cm long

  2 Inflorescence an axillary or terminal raceme, fascicle, cyme, or umbel, of < 20 flowers; leaves herbaceous, deciduous.

        5 Upper surface of leaves bearing dark glandular trichomes along the midrib (most easily seen with a 10× hand lens); shrubs

        5 Upper surface of leaves lacking dark glandular trichomes along the midrib; shrubs and trees.

          6 Ovary and fruit 10-locular; inflorescence a raceme (rarely a fascicle); pome < 1 cm in diameter

          6 Ovary and fruit 5-locular; inflorescence a cyme, umbel, or fascicle (lacking an elongated central axis); pome 0.7-10 cm in diameter.

             7 Styles distinct; exocarps (carpels within pericarp) bony and seedlike; trees and shrubs, with thorns

             7 Styles usually connate at base; exocarps leather or papery and easily opened to expose seeds; small trees, unarmed, or armed with sharp spur branches.

               8 Pome globose to ovoid, lacking stone cells; anthers yellow to white; styles connate at the base; leaves blunt to acuminate; [apples and crabapples]

               8 Pome globose or pyriform, with stone cells; anthers reddish; styles distinct; leaves acute to acuminate; [pears]

1 Ovary superior; fruit dehiscent (aggregate of follicles, or capsule) or indehiscent (drupe, aggregate of drupelets, aggregate of achenes).

                 9 Leaves opposite; fruit an aggregate of usually 3-5 purple to black drupelets; [tribe Kerrieae]

                 9 Leaves alternate; fruit various (see below; if an aggregate of drupelets, then with >5 drupelets).

                   10 Leaves large, > 10 cm wide, palmately veined, palmately lobed; fruit an aggregate of drupelets; [tribe Rubeae]

                   10 Leaves smaller, < 8 cm wide, pinnately veined, either not lobed or basally pinnately lobed; fruit a drupe, a capsule, an aggregate of follicles, or an aggregate of achenes.

                     11 Leaves singly serrate or entire (rarely, as in Prunus americana, irregularly and slightly doubly serrate), not lobed basally.

                       12 Gynoecium of separate carpels; fruit an aggregate of follicles; [tribe Spiraeeae]

                       12 Gynoecium of fused carpels; fruit either a fleshy drupe or a capsule.

                          13 Ovary 5-angled in ×-section; fruit a 5-angled capsule; leaves obovate, obviously broadest towards the tip; [tribe Osmaronieae]

                     11 Leaves doubly serrate, also often lobed towards the base.

                            14 Corolla yellow; stems arching, green; fruit an aggregate of drupe-like achenes (dry and indehiscent); [tribe Kerrieae]

                            14 Corolla white to pink or rose; stems not both arching and green; fruit various (see below).

                              15 Inflorescence a dense, umbel-like corymb; leaf apices rounded to acute; fruit an aggregate of 5 follicles; [tribe Neillieae]

                              15 Inflorescence a raceme or a leafy panicle; leaf apices acuminate.

                                16 Fruit a single follicle; [exotic, planted, and rarely naturalized, as in e. VA]; [tribe Neillieae]

                                16 Fruit an aggregate of 2-4 drupe-like achenes; [rare native of calcareous habitats in sc. TN, nw. GA, n. AL, and disjunct westward in AR and MO]; [tribe Kerrieae]