Plants annual, 3-20 dm; roots also often arising from proximal nodes. Stems scandent, ribbed, glabrous; prickles 1-1.5 mm. Leaves: ocrea brownish, cylindric, (3-)5-13 mm, chartaceous, base inflated or not, without prickles, margins oblique, glabrous or ciliate at tip with bristles 0.2-1 mm, surface glabrous; petiole 0.5-4 cm; blade broadly lanceolate to oblong, 2-8.5 × 1-3 cm, base sagittate to cordate, margins entire, ciliate or eciliate, apex obtuse to acute, faces glabrous or densely appressed-pubescent, usually with retrorse prickles along midvein abaxially. Inflorescences capitate or paniclelike, uninterrupted, 5-15 × 4-10 mm; peduncle 10-80 mm, usually glabrous, sometimes with retrorse prickles proximally; ocreolae overlapping, margins eciliate. Pedicels mostly ascending, 1-1.5 mm. Flowers 2-3 per ocreate fascicle; perianth white or greenish white, often tinged pink or red, sometimes entirely pink, glabrous, accrescent, not becoming blue and fleshy in fruit; tepals 5, connate 1/ 1/ 2 their length, broadly elliptic, 3-5 mm, apex obtuse; stamens 8, filaments distinct, free; anthers pink, ovate; styles 3, connate to middle. Achenes included or styles exserted, light or dark brown to black, 3-gonous, 2.5-4 × 1.8-2.5 mm, dull to shiny, smooth to minutely punctate. 2n = 40.
Moist shaded sites, meadows, pastures, fens, swamps, shorelines of ponds and streams; at elevations up to 1,000 metres. Ditches in Kerry.