General description:- Herbs, shrubs or climbers.
Leaves:- Nearly always alternate; stipules often united to form a membranous sheath (ochrea).
Flowers:- Hermaphrodite or unisexual; perianth 3- to 6-merous, herbaceous, often enlarging and becoming membranous in fruit. Stamens usually 6-9. Ovary superior, single celled (unilocular); styles 2-4; ovule solitary, basal.
Fruit:- An obtusely 3-angled (trigonous) or discoid with a convex lens-shape (lenticular) nut.
ATRAPHAXIS
General description:- Erect, small-leaved shrubs.
Ochreae brown proximally, hyaline distally, bifid, 2-veined. Flowers hermaphrodite, in short racemes. Perianth-segments 4 or 5, the inner 2 or 3, accrescent and surrounding the fruit. Stamens 6 or 8, united into a ring at the base. Stigmas 2 or 3; nut not winged.
1) Leaves less than 2 cm; flowers in short racemes
EMEX
General description:- Monoecious annuals. Ochreae not fringed with hairs (not ciliate), soon irregularly lobed at the margin - as if torn (lacerate).
Flowers:- Female at the base of the inflorescence; perianth-segments 6, free in male flowers, united (connate) in the female flowers, the outer 3 ending in a sharp point (spinescent) and hardened (indurate) in fruit. Stamens 4-6. Stigmas 3.
Fruit:- Nut triquetrous, included in the perianth.
Key features:-
1) Herbs or dwarf shrubs
2) Outer fruiting perianth-segments with 3 stout spines
FALLOPIA
General description:- Herbs or dwarf shrubs.
Stem:- Twining or procumbent
Leaves:- Deltate or cordate-sagittate, petiolate. Ochreae truncate.
Flowers:- In lax, spike-like or paniculate terminal and lateral inflorescences. Perianth-segments 5(6); the outer 3 larger, keeled or winged. Stamens 8. Stigmas capitate, subsessile. Not triquetrous, not exceeding the perianth.
Key features:-
1) Perianth-segments 5 or 6.
2) Woody climbers.
3) Leaves 3-6 cm wide, cordate.
4) Perianth-segments 5, equal in fruit or the outer larger.
5) Outer perianth-segments winged or keeled in fruit.
6) Twining annuals.
7) Stigmas compact, subsessile.
PERSICARIA
General description:- Herbs or dwarf shrubs.
Leaves:- Variously shaped, always distinctly longer than wide.
Flowers:- Perianth-segments usually more or less equal, free or united in lower part, petaloid at least in part, not winged or keeled. Stamens 8, rarely fewer. Stigmas 2 or 3.
Fruit:- Nut lenticular or obtusely 3-angled (trigonous), not winged, enclosed in the persistent perianth or protruding from it for less than ½ its length.
Key features:-
1) Peduncles without glands.
2) perianth bright or pale pink.
3) Leaves lanceolate; distinctly longer than wide, never deltate and rarely cordate.
4) Fruit included in the perianth or protruding for less than ½ its length.
Sect. PERSICARIA.
Ochreae:- Usually brownish, entire or ciliate but not lacerate.
Flowers:- In spikes; bracts few and inconspicuous. Perianth usually petaloid; stamens 5-8; styles 2, rarely 3, united below.
Fruit:- Nut lenticular or trigonous.
COMMENT
Extremely variable, especially in habit, colour of foliar glands and of perianth, and in indumentum. Its widespread dissemination as a weed has obscured any geographical pattern which may have existed, and there is scarcely any correlation of these characters that remains constant over a wide area. Furthermore, it is known that some of the characters, especially of habit and tomentum, which are partly determined genetically, are also very plastic phenotypically.
POLYGONUM
General description:- Herbs or dwarf shrubs.
Leaves:- Variously shaped, always distinctly longer than wide.
Flowers:- Perianth-segments usually more or less equal, free or united in lower part, petaloid at least in part, not winged or keeled. Stamens 8, rarely fewer. Stigmas 2 or 3.
Fruit:- Nut lenticular or obtusely 3-angled (trigonous), not winged, enclosed in the persistent perianth or protruding from it for less than ½ its length.
Key features:-
1) Leaves distinctly longer than wide, never triangular-shaped (deltate) and rarely heart-shaped (cordate).
2) Fruit included in the perianth or protruding for less than ½ its length.
Sect. POLYGONUM
General description:- Herbs or dwarf shrubs.
Leaves:- Small; ochreae silvery- or whitish-hyaline, at least in upper part, usually eventually irregularly lobed at the margin (lacerate).
Flowers:- Axillary, solitary or in small clusters, forming very lax spikes. Perianth petaloid to more or less sepaloid; stamens 3-8; styles 3 (rarely 2), usually short;
Fruit:- Nut usually trigonous.
P. AVICULARE Group
General description:- Annuals.
Stems:- Erect, ascending or procumbent, 10-60 cm.
Leaves:- Variable in shape and size, entire, acute to obtuse, green or somewhat glaucous. Ochreae silvery-hyaline, often brownish near the base, with few, faint veins, lacerate.
Flowers:- Solitary or in axillary clusters of 2-6; bracts leaf-like. Perianth-segments greenish with white, pink or reddish margins.
Fruit:- Nut 1·5-4 mm, dotted (punctulate), dull, included in or slightly exserted from the perianth.
Key features:-
1) Perianth-segments at least as long as the tube.
2) Leaves linear to elliptical.
3) Bracts all leaf-like, longer than the flowers.
4) Nut punctulate, dull, enclosed in the perianth or slightly exceeding it.
RUMEX
General description:- Herbs, rarely shrubs, usually with long, stout roots, sometimes rhizomatous.
Leaves:- Alternate; ochreae tubular.
Flowers:- Hermaphrodite or unisexual, arranged in whorls on simple or branched inflorescences, wind-pollinated (anemophilous). Perianth-segments in 2 whorls of 3, the outer remaining small and thin, the inner becoming enlarged and often hardened in fruit. Valves (fruiting inner perianth-segments) sometimes developing marginal teeth or dorsal tubercles as they mature. Stamens in 2 whorls of 3; anthers attached to the filament by the base (basifixed).
Fruit:- A trigonous nut.
Subgen. ACETOSA
General description:- Dioecious or polygamous, rarely monoecious.
Leaves:- Usually hastate or sagittate, often with acid taste.
Subgen. ACETOSELLA
General description:- Slender perennials with acid taste.
Leaves:- Hastate or sagittate, sometimes with several pairs of basal lobes.
Flowers:- Valves seldom much longer than the nut, without tubercles.
Key features:-
1) Stamens 6- 8.
2) Leaves at least 2 cm; not palmately lobed.
3) Flowers in panicles.
4) Stamens 8 or fewer.
5) Perianth-segments 6, the inner much larger than the outer in fruit.
Subgen. PLATYPODIUM
General description:- Usually annual.
Leaves:- Basal, small, lanceolate, ovate or spathulate.
Flowers:- In clusters of 4 or fewer. Flowers, fruits and pedicels often heteromorphic; valves very small, usually with teeth and small tubercles.
Subgen. RUMEX
Leaves:- Basal and lower cauline never hastate or sagittate.
Flowers:- All or most hermaphrodite. Valves several times as wide as the nut, with or without tubercles.