Curcuma ubonensis (Zingiberaceae), a new species of Curcuma subgen. hitcheniopsis from Eastern Thailand

Curcuma ubonensis Boonma, Saensouk, Maknoi & P. Saensouk sp. nov. (Zingiberaceae) was recently discovered in Ubon Ratchathani Province, Eastern Thailand. Specimen identification involves comparing their morphology with descriptions in similar species' protologues. We performed measurements on specimens collected from their natural habitats, both living and preserved. Despite its resemblances with Curcuma prasina Škorničk. in having greenish inflorescence with small purple flowers that lack of epigynous glands, yet this novel species displays distinct features of a brownish-red margin of petiole (vs. C. prasina has green margin), lamina elliptic, 3.8-7.0 cm wide, margin brownish red (vs. narrowly elliptic, 1.5-3.2 cm wide, margin green); coma bract present (vs. absent), fertile bracts uniquely triangular-obovate, apex rounded (vs. almost orbicular, apex acute), and labellum reddish purple with four white stripes by two stripes rarely pale yellow extending from the basal to half of the sinus, and another two stripes from the basal along the longitudinally of each lobe to half the length of the lobe, with yellow at the middle groove of the labellum almost to the base (vs. purple with a bright yellow and swollen median band composed of two central lines extending from the base to about two-thirds the length of the labellum towards the apex, sides of the labellum with paler lines radiating towards the margin). Meticulous examination and morphological comparison of Curcuma ubonensis with related species within the Curcuma genus reveals its novelty. We comprehensively accounted for its morphological traits, including illustrations, vernacular name, ecological preferences, phenology, distribution, traditional uses, conservation status, distribution map, and a comparative table to its ally species. Furthermore, we present an updated identification key for differentiating species within the Curcuma subgenus Hitcheniopsis in Thailand.