Erect (rarely procumbent) single-stemmed unbranched (rarely branched) annual herb; stems up to 60 cm long, sparsely to densely pilose with shiny many-celled hairs, sometimes also with a band of puberulous hairs. Leaves: some or all whorls with one pair more than 5 times longer than the other, but some often subequal; lamina narrowly ovate or narrowly elliptic, largest 6.5–22≈0.5–1.9 cm, margin of larger with 3–13 widely spaced teeth per side, of smaller with 3–5 larger teeth per side, sparsely pubescent (or pilose along midrib), hispid-puberulous above. Heads dense, near top of stems; peduncle (0.5–)1–7(–12) cm long, usually ± deflexed, indumentum as stems; axes puberulous to pubescent, with capitate glands; floral leaves and outer bracts narrowly ovate to narrowly elliptic, up to 7(–9) cm long, pubescent to pilose, ± capitate glands; inner bracts similar, up to 23 mm long, with capitate glands. Sepals puberulous to pubescent (often also with long shiny many-celled hairs), with capitate glands; dorsal ovate, 20–27 mm long, narrowing gradually to apex or with slightly ligulate apical part, apex acute, lateral teeth absent; ventral narrowly ovate-elliptic, 17–24 mm long, not ligulate, bifid, usually also with 1(–2) central teeth and with 1–3 lateral teeth per side; lateral 18–26 mm long. Corolla blue to dark blue or mauve, 18–26 mm long of which the tube 5–8 mm; limb very indistinctly lobed, without capitate glands below, callus with 3 equally strong ribs and 3 large apical flanges (or central weaker). Filaments 4–7 mm long, sparsely glandular; tooth 1–1.5 mm long, rounded, curved or straight; anthers 3–4 mm long. Capsule ± 13 mm long. Seed ± 11≈7 mm.