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| Nepenthes siamensis Nuanlaong in Nuanlaong, Yodthammarat, Chiwan, Laewan et Pohsap, 2026. Drawn by Chayan Yodthammarat |
Summary
Nepenthes siamensis, a new species from Khlong Phanom National Park in southern Thailand, is described. This species, closely related to others in section Montanae, stands out due to its distinct inflorescence characteristics, including bracts present on both male and female flowers, and unique pitcher morphology. It is found approximately 650 km north of the most similar species based on morphological comparison, N. sanguinea and N. thai, which are also both terrestrial and lower montane. It shares characters with them, such as a climbing habit and oblong to subspathulate leaves with 2 – 3 longitudinal nerves on each side of the midrib. This discovery significantly extends the known range of section Montanae.
Key Words: Carnivorous plants, pitcher plant, taxonomy
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| Nepenthes siamensis. A stem with leaves and upper pitchers; B lower pitcher; C male inflorescence; D female flowers; E male flowers; F lower surface of lid with upper part of peristome; G upper surface of lid; H – J nectar glands. From live specimens. Drawn by Chayan Yodthammarat |
Nepenthes siamensis Nuanlaong sp. nov.
Type: Thailand, Surat Thani Province, Phanom Distr., Khlong Phanom National Park, ...
Recognition. This species differs from Nepenthes thai in leaf base margins clasping the stem for ½ of the circumference, not decurrent (vs clasping stem ¾ – ⅚ of circumference, bases decurrent down the stem for 3 – 12 mm in N. thai); lower pitcher cylindrical in lower ¾ of length, infundibular in upper ¼ (vs ovoid-cylindrical); spur filiform (vs branched); bracts present on all flowers at the bases of pedicels in the male inflorescence and on the lower half of the pedicel in the female inflorescence (vs bract absent).
Sunya Nuanlaong, Chayan Yodthammarat, Purin Chiwan, Teerayut Laewan and Suphansiri Pohsap. 2026. Nepenthes siamensis (Nepenthaceae), A New Species of Section Montanae from Surat Thani Province, Peninsular Thailand. Kew Bulletin. DOI: doi.org/10.1007/s12225-025-10336-2 [27 February 2026]
