Plants perennial, glabrous; with vertical rootstock, occasionally with short, creeping rhizomes. Stems erect or ascending, usually producing axillary shoots below 1st-order inflorescence or at proximal nodes, 30-60(-90) cm. Leaf blades light green to yellowish green, linear-lanceolate, occasionally lanceolate, 6-14 × 1-3.5(-4) cm, usually ca. 5-7 times as long as wide, widest near middle, thin, not coriaceous, base cuneate, margins entire, flat or undulate, apex acute or attenuate. Inflorescences terminal and axillary, terminal usually occupying distal 5- 3 of stem, rather dense or interrupted in proximal 1/2, usually broadly paniculate (branches simple or with few 2d-order branches). Pedicels articulated in proximal 1/ 3 or almost near base, filiform (thickened distally), 4-7 mm, not more than 2-2.5 times as long as inner tepals, articulation indistinctly swollen. Flowers 10-20 in whorls; inner tepals broadly ovate-triangular, occasionally broadly triangular, 3.5-4.5(-5) × 3.5-4(-5) mm, base truncate or indistinctly cordate, margins entire or indistinctly erose, apex obtuse or subacute; tubercles 3, equal or subequal (much narrower than inner tepals). Achenes brown or dark reddish brown, 2-3 × 1.5-2 mm. 2n = 40.

Flowering spring-early summer. Shores of streams and rivers, wet meadows; 1000 m; N.Mex.; Mexico.

Some authors recognize Rumex mexicanus in the broad sense, including in it many other taxa treated here as separate entities. For consistency, the entities of the R. salicifolius aggregate that are recognized herein are kept separate pending additional taxonomic research.

Duration: Perennial

Nativity: Native

Lifeform: Forb/Herb

General: Perennial herb, 30-90 cm tall, from vertical rootstock and occasionally short, creeping rhizomes; stems erect, usually much-branched; herbage glabrous.

Leaves: Alternate along the stems; blades linear-lanceolate to linear-oblong,  6-14 cm long and 1-4 cm wide, widest near the middle, thin and light green or yellow-green, with entire to slightly undulate margins. Ocrea (stipules fused into a sheath which surrounds the stem at the base of each leaf) thin, papery, early-deciduous.

Flowers: Greenish to reddish, in dense panicles with ascending branches lined with whorls of 10-20 flowers; each flower has 3 bract-like green-brown to red-brown outer tepals and 3 winged inner tepals called valves which enlarge to 4 mm long in fruit, the wings forming a broadly ovate-triangular shape with entire or slightly irregularly toothed margins; each valve usually has a grain-like tubercle called a callosity.

Fruits: Achenes 2-3 mm long, brown to dark red-brown, surrounded by the 3 enlarged inner tepals (valves).

Ecology: Found in waste ground, shores of streams and rivers, and wet meadows, from 4,000-6,500 ft (1219-1981 m); flowers June-September.

Distribution: NM and MEX

Notes: This perennial is distinguished from other Rumex species based on its leaves, which are narrow, hence the common name willow-leaf dock, and alternate along the stems but not clustered in a basal rosette. The leaves are widest near the middle, usually less than 3 cm wide, never have a pair of lobes at the base of the leaf blades, and the edges can be smooth or slightly undulate. This species has previously been included in R. salicifolius.

Ethnobotany: Leaves were eaten as greens, Used medicinally to treat fevers, burns, intestinal disorders, liver problems, swellings, painful joints, and sore throats. Interestingly the White Mountain Apache and Zuni used the plant to help childless women become pregnant, while the Houma used it as an abortifacient.

Etymology: Rumex is the classical Latin name for dock, possibly derived from rumo, to suck, in reference to the practice of sucking the leaves to allay thirst; mexicanus means of or from Mexico.

Synonyms: Rumex salicifolius var. mexicanus

Editor: AHazelton 2017