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| 1 Leaf blades of well-developed leaves (at least) hastate or sagittate; plants dioecious (rarely polygamo-monoecious), the flowers mostly unisexual; fresh foliage pleasantly acid to taste. |
| ..2 Well-developed leaves with sagittate base (the lobes pointing downward, essentially parallel to the petiole); inner tepals of carpellate flowers 4-6 mm long (at fruiting), 1 or more with a tubercle; tepals of staminate flowers 2.0-3.0 mm long; achenes 2.0-2.5 mm long; plant perennial from a rhizome; [subgenus Acetosa; section Acetosa] |
| ..2 Well-developed leaves with hastate base (the lobes divergent, pointing outward, at about 90 degrees from the petiole); inner tepals of carpellate flowers 1.2-3.5 mm long (at fruiting), none with a tubercle; tepals of staminate flowers 1.5-2.0 mm long; achenes 0.9-1.5 mm long; plant either perennial from a rhizome or annual from a taproot. |
| ....3 Inner tepals (at fruiting) 2.5-3.2 mm long, much longer and wider than the achene, with an expanded, accrescent wing that develops prominent reticulate veins; pedicel jointed near its middle or base, well below the tepals; plants annual or short-lived perennial; from a taproot; [subgenus Acetosa; section Americanae] |
| ....3 Inner tepals (at fruiting) 1.2-1.7 (-2.0) mm long, about as long and wide as the achene, with a minute or absent free wing; pedicel jointed just below the tepals; plant perennial, from a thin, creeping rhizome; [subgenus Acetosella] |
| ......4 Tepals loosely investing the ripe achene (easily rubbed off by rolling the achenes between finger and thumb) |
| ......4 Tepals tightly adherent to the ripe achene (not able to be rubbed off) |
| 1 Leaf blades not hastate or sagittate; plants synoecious (rarely with some dioecious or polygamo-monoecious individuals), the flowers normally bisexual (sometimes bisexual and unisexual flowers in the same inflorescence); fresh foliage “green” or bitter to taste; [subgenus Rumex]. |
| ........5 Leaves primarily cauline; inner tepal margins entire; [subgenus Rumex; section Axillares]. |
| ..........6 Pedicels 2.5-5× as long as the inner tepals; pedicel joint below the midpoint of the pedicel. |
| ............ 7 Leaf blades ca. 2× as long as wide; lateral veins of leaves forming angle of ca. 80° to midvein |
| ............ 7 Leaf blades 3-7 (-10)× as long as wide; lateral veins of leaves forming angle of 40-60° to midvein. |
| ............ ..8 Leaf blades 3-5 (-6)× as long as wide; coriaceous and usually somewhat fleshy; inflorescences dense (interrupted only at base); pedicels 2.5-3× as long as the inner tepals; inner tepals as wide as or wider than long |
| ............ ..8 Leaf blades 5-7 (-10)× as long as wide; thin; inflorescences interrupted in at least the lower half; pedicels 3-5× as long as the inner tepals; inner tepals longer than wide (rarely as long as wide) |
| ..........6 Pedicels usually < 2.5× as long as the inner tepals; pedicel joint either the midpoint of the pedicel, or below it. |
| ............ ....9 Leaf blades widest toward the apex; leaf apex rounded or obtuse |
| ............ ....9 Leaf blades widest at the middle or toward the base; leaf apex acute (rarely nearly obtuse). |
| ............ ......10 Leaf blades widest toward the base; inner sepals 4.5-6 mm long, 3-4.5 (-6) mm wide |
| ............ ......10 Leaf blades widest near the middle; inner sepals (2-) 2.5-4.5 (-5) mm long, (2-) 2.5-4 (-4.5) mm wide. |
| ............ ........11 Inflorescence lax, distinctly interrupted; leaf blades thick and coriaceous, deep green, with veins prominent on the lower surface; leaf apex nearly obtuse; inner sepals 3.5-4.5 (-5) mm long, 3-4 (-4.5) mm wide |
| ............ ........11 Inflorescence dense, interrupted only toward its base; leaf blades light or yellowish green, the veins on the lower surface not noticeably prominent; leaf apex acute; inner sepals (2-) 2.5-3.5 (-3.8) mm long, (2-) 2.5-3 (-3.5) mm wide |
| ........5 Leaves basally disposed, the largest and best developed in a basal rosette (these sometimes withering at maturity, especially in annual species); inner tepal margins entire or variously dentate; [subgenus Rumex; section Rumex]. |
| ............ ..........12 Inner tepal margins entire, indistinctly erose, or (rarely) minutely denticulate (the teeth then < 0.2 mm long). |
| ............ ............ 13 Inner tepals ca. 2× as long as wide, margins entire, largest tubercle almost as wide as the inner tepal. |
| ............ ............ ..14 Tubercles 3, equal or nearly so in size; inflorescence leafy through at least 2/3 of its length; pedicels 1.4 (-5) mm long |
| ............ ............ ..14 Tubercles 1 (or if 3, then one much larger than the other 2); inflorescence leafy only in basal 1/3 or less of its length; pedicels (2-) 4-6 (-8) mm long |
| ............ ............ 13 Inner tepals ca. 1-1.5× as long as wide, margins entire or denticulate, largest tubercle much narrower than the inner tepal. |
| ............ ............ ....15 Tubercles 3, equal or nearly so in size; leaf blade >8× as long as wide, 20-55 (-70) cm long, 2-7 cm wide |
| ............ ............ ....15 Tubercles 1 or 2-3 (if 2-3, then one much larger than the other 1-2); leaf blade <6× as long as wide, 15-45 (-50) cm long, either 2-6 cm or 10-15 cm wide. |
............ ............ ......16 Leaf blade 15-30 (-35) cm long, 2-6 cm wide, the margins strongly undulate; inner tepals 3.5-6 mm long; tubercles normally 3 (rarely 1-2) |
| ............ ............ ......16 Leaf blade 30-45 (-50) cm long, 10-15 cm wide; the margins plane or weakly undulate; inner tepals (5-) 5.5-8 (-10) mm long; tubercles normally 1 (rarely 2-3) |
| ............ ..........12 Inner tepal margins prominently dentate, at least some of the teeth > 0.3 mm long. |
| ............ ............ ........17 Inner tepals (not including the teeth) orbiculate-ovate to deltate, as wide as long |
| ............ ............ ........17 Inner tepals (not including the teeth) ovate-triangular or triangular, evidently longer than wide. |
| ............ ............ ..........18 Inner tepals with 3-5 strongly hooked teeth on each side |
| ............ ............ ..........18 Inner tepals with straight teeth. |
| ............ ............ ............ 19 Leaf blade > 4× as long as wide; inner tepals (not including the teeth) ca. 2× as long as wide |
| ............ ............ ............ 19 Leaf blade 2-3× as long as wide; inner tepals (not including the teeth ca. 1.5× as long as wide (sometimes to 2× as long as wide in R. obtusifolius). |
| ............ ............ ............ ..20 Plants perennial; base of leaf blade usually distinctly cordate. |
| ............ ............ ............ ....21 Stems 6-12 (-15) dm tall; leaf blades 20-40 cm long; inflorescence branches normally ascending, making an angle of 30-45° with inflorescence axis; tubercles of the inner sepals smooth |
| ............ ............ ............ ....21 Stems 2-6 (-7) dm tall; leaf blades 4-10 (-15) cm long; inflorescence branches spreading, making an angle of 60-90° with inflorescence axis; tubercles of the inner sepals usually verrucose |
| ............ ............ ............ ..20 Plants annual or biennial; base of leaf blade cuneate (rarely rounded). |
| ............ ............ ............ ......22 Inner tepals 4-5 (-5.5) mm long; tubercles of the inner sepals verrucose |
| ............ ............ ............ ......22 Inner tepals 3-4 mm long; tubercles of the inner sepals smooth or minutely punctate |