Erect herb, branched and sometimes woody at the base, often with white papery bark, 16–60 cm. tall, very similar to the previous species but with larger flowers; rootstock often practically unbranched.. Leaves paired but sometimes appearing pseudoverticillate due to arrested axillary branchlets; blades lanceolate or oblong-lanceolate to linear-lanceolate, (2.5–)3.7–7.5 cm. long, 0.35–1.45(–2.3) cm. wide (sometimes appearing narrower when the margins are revolute), acute at the apex, cuneate at the base, glabrescent or with short white bristly hairs above and beneath; petiole 0–0.7 mm. long; stipules with ± 7 setae, 0.8–4 mm. long from a base 2–5 mm. long.. Inflorescence a dense terminal head 0.7–2.3 cm. wide, not elongating to any extent; peduncle 0.4–5.8(–7.8) cm. long.. Flowers white or pale blue.. Calyx pubescent; tube 2–3(–4) mm. long, 1.5–2.5 mm. wide; the foliaceous lobe lanceolate, 0.6–2 cm. long, 1–2.5 mm. wide, the rest reduced to tufts of hairs.. Corolla-tube 2.5–4.3 cm. long, 1.5–2.5(–3) mm. wide at the apex, 1.5 mm. wide at the base, mostly with stubby indumentum similar to P. ouranogyne; lobes oblong-elliptic, (3–)4.5–7.5 mm. long, (1–)1.5–3 mm. wide.. Ovary and fruit 3–5-locular; style exserted 2–4 mm. in long-styled flowers; stigma 3–5-fid, the lobes filiform, 1–2 mm. long.. Fruit very similar to that of P. ouranogyne, very pale brown, globose, 4.5–5.5 mm. long, 4–6 mm. across, the walls thick and woody.. Seeds as in P. ouranogyne.
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