Thai Forest Bulletin (Botany)

Ten new species of Didymocarpus (Gesneriaceae: Didymocarpoideae) from Thailand

Pranee Nangngam — 2026-08-19

Ten new species of the genus Didymocarpus are described from Thailand: Didymocarpus alboroseus, D. flaviflorus Nangngam, D. hongsonensis Nangngam, D. kiewbangii, D. kwanjaiae, D. mekongensis, D. niveus, D. phuwuaensis, D. suchartii Nangngam and D. vilaiwaniae. Full descriptions, distributions, ecology and colour plates are provided for all taxa. These additional new species increase the total number of Didymocarpus in Thailand to thirty-five species, and therefore, a key to the species of Didymocarpus in Thailand is also provided in this paper.

Pseuderanthemum multiflorum (Acanthaceae), a new species from Thailand

Thiamhathai Choopan — 2026-08-17

Pseuderanthemum multiflorum (Acanthaceae), a new species known only from Thailand, is here described and illustrated. It is distinguished from P. graciliflorum by inner corolla tube and pistil being glabrous instead of puberulous and by calyx lobes 4.5–6 mm long instead of 3–4 mm long. Comparison of morphological characteristics are provided.

Pennilabium labanyaeanum (Orchidaceae), a new record for Thailand

Sathien Damapong — 2026-08-13

Pennilabium labanyaeanum, previously known only from Meghalaya in Northeast India, is reported from Doi Pha Hom Pok National Park, Chiang Mai Province, Thailand. The morphological description, detailed line drawing, coloured photos, and an identification key were provided for this new species record.

Two new species, three new records and taxonomic notes of Rhododendron (Ericaceae) in Thailand

Maneenuch Tubtamat — 2026-08-10

Two new species, Rhododendron trichopetalum and R. yalaense, from Peninsular Thailand, are described and illustrated. Three new records of R. jasminiflorum, R. klossii and R. robinsonii are newly reported for Thailand, and R. klossii is herein reinstated. Lectotypifications were designated where required and an updated key to species, modified from the Flora of Thailand, is provided.

Reinstatement of Lithocarpus longispinus (Fagaceae): a species confined to the Malay Peninsula (southern Thailand and Peninsular Malaysia)

Wei Harn Tan — 2026-08-07

Lithocarpus is a major Asian endemic genus of (sub)tropical trees found throughout the region. The nearly 350 species can be difficult to identify in the absence of good fruiting material, often leading to confusion and misidentification. Once recognized as a distinct species, Lithocarpus longispinus is currently a heterotypic synonym of Lithocarpus wrayi. Following careful examinations and comparisons of herbarium specimens throughout the distribution range, along with in situ collections, we find distinct morphological differences between the two species. Here we define the diagnostic morphological traits, provide a complete description of the species along with an initial conservation assessment and propose the reinstatement of L. longispinus.

Notes on the genus Thismia (Thismiaceae) in Cambodia

Savin Kin — 2026-07-08

The genus Thismia in Bokor National Park, Cambodia has been studied based on literature and recent collections from field surveys. Three species are recorded including T. bokorensis, T. filiformis, and T. gardneriana, all belonging to sect. Thismia. A key to species of the genus Thismia in Cambodia, descriptions and photographs of T. filiformis, and T. gardneriana are provided. In addition, the preliminary conservation status was assessed following the International Union for Conservation of Nature (IUCN) Red List criteria.

Lepidagathis (Acanthaceae) of Thailand: New Species and Updated Synopsis

Chortip Kantachot — 2026-07-02

In this synopsis of the genus Lepidagathis for the Flora of Thailand, nine species are recognized. This includes Lepidagathis argentea, a new species collected from limestone bedrock in Tak Province, and three species newly recorded for Thailand, L. dulcis, L. purpuricaulis and L. thorelii. Lepidagathis chiengmaiensis and L. thyrsiflora, are reduced to synonyms of L. incurva and L. fasciculata, respectively. The following names have been lectotypified: Lepidagathis chiengmaiensis, L. chlorostachya, L. dissimilis, L. dulcis, L. falcata and L. thorelii. A genus description with key to species, nomenclatural notes, distributional data and specimens examined are provided.