Flora of the Southeastern United States
2022 Edition

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Key to Rumex

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