Rheum ×rhabarbarum L.

Glabrous herb. Lvs mostly radical, arising from thick woody rhizomes. Petiole to c. 60 × 3 cm, flattened above and with raised margins, ± crimson, especially towards base; ochreae to c. 8 cm long, brown, scarious. Lamina to c. 50 × 40 cm (larger in cultivation); main veins 7, prominently raised below; margins ± undulate. Infl. to c. 1.5 m tall; main stem massive and hollow; lateral branches numerous. Bracts minute. Fls greenish white; pedicels filiform, jointed, commonly c. 5 mm long. Inner 3 perianth segments 2.5–3 mm long, elliptic to suborbicular; outer 3 segments smaller. Stigmas large, irregular in outline. Fr. to c. 1 cm long; wings broad, reddish.

[From: Webb et al. (1988) Flora of New Zealand. Volume 4.]