Boesenbergia isanensis (Zingiberaceae), a New Species from Thailand

Boesenbergia isanensis is similar to B. rotunda (L.) Mansf. but it differs in the plant size 70–80 cm tall, the rhizome dark yellow inside, the root dark yellow inside, the leaf blades glabrous and dark red on the midrib of the upper surface, densely pubescent on the lower surface, and the cream coloured flowers, with labellum red in the apical half and cream in the basal half, pubescent at centre.

Perennial herb, 70–80 cm tall to the top of leaf blades. Rhizomes are short, outside dark brown, inside dark yellow, bearing tubular storage roots. Roots yellow outside, dark yellow inside. Bladeless leaf sheaths 6–7, 19.5–21 cm long, dark green, pubescent; foliage leaves 5–6; leaf sheaths 19.5–21 cm long, dark green, densely pubescent; ligules broadly oblong, 1–1.7 × 0.8–1 cm, bilobed, hairy; petioles 5–9 cm long, dark green, sparsely pubescent; blade elliptic-oblong, 20–27 × 4–10 cm, apex acute-acuminate, base attenuate, upper surface dark green with dark red midribs, glabrous, lower surface greenish, densely pubescent. Inflorescence terminal, 6–7 cm long, with ca. 7 flowers opening 1 (or 2 to 3) after another; peduncle 1.5–2 cm long, sparsely pubescent, enclosed in the leaf sheaths. Bract 1 per flower, green, lanceolate, sparsely pubescent, appearing only in the rainy season.