Shrubby herb or shrub to 3 m tall; young stems glabrous. Leaves with petiole 0.5–2(–2.5) cm long; lamina narrowly elliptic to elliptic or obovate in outline, largest 13–37≈5–15 cm, deeply lobed with large triangular spine-tipped lobes, each lobe with a spine on antrorse side, apex acuminate to cuspidate, spine-tipped, base attenuate to cuneate, glabrous; each node with one to several persistent sharp terete straw-coloured interpetiolar downwardly directed pungent pale yellow spines to 1.5 cm long, occasionally some with a small lamina. Cymes solitary or also 2 from upper leaf-pair, (5–)7–30 cm long; rachis upwards pubescent and with few to many short to long capitate glands, with several pairs of sterile bracts at base, sometimes merging into the vegetative leaves; bracts green to purplish, ovate to elliptic, finely puberulous to sparsely pubescent and upwards with few to many stalked capitate glands, 1.4–2.8 cm long in middle of cyme, spine-tipped and with 4–8 teeth per side (rarely entire); bracteoles subulate to linear, 5–11 mm long, entire. Calyx green to purplish, puberulous and with few to many stalked capitate glands; dorsal and ventral sepals longer than bract, oblong-obovate, similar or dorsal slightly longer, 2.1–4 cm long, dorsal entire or 2–3-toothed, ventral 2–3-toothed or irregularly toothed, lateral lanceolate, 1.3–2.5 cm long, acuminate. Corolla dark blue to dark purple (rarely pale blue to almost white); tube 4–5 mm long below thickened rim which is 3–4 mm long; limb 5-lobed, 3.5–5≈3.5–5 cm, below puberulous and with capitate glands, above glabrous; callus with narrow central groove. Filaments 1.7–2.2 cm long, glabrous or with stalked glands near apex; anthers 6–9 mm long, densely glandular dorsally. Capsule 2.3–2.5 cm long. Seed ellipsoid to round, 9–10 mm long, glabrous.