Nepenthes kerrii — Vorstman's Guide to the Carnivorous Plants

Identification

A climber to about four metres, with a round, usually unbranched stem three to five millimetres thick that can support itself, green to red in colour. The leaves are sessile and leathery, obovate, to 31 cm long but only 3 cm wide, light green with a green to red midrib. Lower pitchers are ovate, to 14 cm tall and 6 cm wide, orange with red blotches, with fringed wings up to eight millimetres, a cylindrical peristome up to twelve millimetres wide with small teeth, and a round lid with a wavy margin. Upper pitchers are tubular, to 15 cm tall, green to yellow, with red blotches inside, a lobed peristome with a distinct neck, striped yellow or red, and a lid often red beneath. The plant has a well-developed rootstock, and the seeds have strikingly small wings.

Similar species

The closest relative is Nepenthes kongkandana from south-eastern Thailand. According to the literature, kerrii has narrowly ovate rather than tubular lower pitchers, tendrils two to three times as long as the pitcher instead of about equal, a lobed and striped peristome on the upper pitchers, and wing-fringe spacing of four to six rather than ten to twelve millimetres. Other relatives, Nepenthes andamana, Nepenthes bokorensis and Nepenthes suratensis, have linear to lanceolate rather than obovate leaves. The plants of the Malaysian island of Langkawi, formerly included in this species, were described in 2024 as Nepenthes ridzaiana.

The trap and how it works

A pitfall trap with two clearly different pitchers. The ovate, orange and red-blotched lower pitchers stand on the ground with broad fringed wings; the tubular, paler upper pitchers hang from long, coiled tendrils. The peristome of the upper pitchers is lobed and forms a 'neck', an unusual structure within the group. The large inflorescence, up to 130 cm, rises well above the vegetation. Nothing on this species' prey was found in the sources consulted.

Habitat and ecology

Open savanna and grassland on sandy soil, at 400 to 500 m (W5, D2, D4). The soil is a quartz-rich layer up to thirty centimetres deep over granite, which turns hot and hard in the dry season. The plant survives that period with its rootstock, like other pyrophytes of the group. It does not grow alongside any other pitcher plant.

Distribution and elevation

Endemic to Thailand, on the island of Tarutao in Tarutao National Marine Park, Satun Province, in the far south-west of the country. Our own list says 'Thailand'; the restriction to Tarutao comes from the literature. The plants of Langkawi, about ten kilometres further south, were previously also regarded as kerrii, but since 2024 form a separate species. Before it was named, the species was listed by Stewart McPherson (2009) as 'N. sp. Trang'.

Recorded (one-degree cells)

Distribution based solely on records at GBIF (Global Biodiversity Information Facility), not on TDWG regions — those are often far larger than the actual range. The light halo is the area around a record, the dark core the record itself. The darker square is the only one-degree cell — roughly a hundred and ten kilometres — in which the species has been recorded, from all GBIF records. This is coarser than for most species because hardly any record of this plant carries an accurate coordinate. It shows where the species has been seen, not where it occurs: an empty square means nothing.

Forms and variation

No varieties are recognised, and no natural hybrids are known, which is logical since the species does not grow with other pitcher plants. Stems and midribs vary from green to red, lower pitchers from orange to red-blotched, upper pitchers from green to yellow. The splitting off of the Langkawi plants means that older descriptions of kerrii sometimes combine material of two species.

Where and when to see it

Tarutao is reachable only by boat and lies in a national park that is open outside the rainy season, roughly from November to May. According to McPherson the sites on the grassy hills of the interior are extremely inaccessible; a visit requires permission from the park authorities and an experienced guide. The island itself, with its forest, beaches and history, is worth the trip even if the pitcher plants stay out of reach.

Conservation status

The Red List assesses the species as Least Concern, in an assessment from 2018. Its sites lie within a national marine park and, according to McPherson, are so hard to reach that the populations are not threatened. A small range on a single island nonetheless remains sensitive to changes in fire regime. As a member of Nepenthes it is listed in CITES Appendix II, so international trade in wild plants requires a permit.

Scientific name

Nepenthes kerrii | Catalano & Kruetreepradit, 2010

Nepenthes kerrii was described in 2010 by Marcello Catalano and Trongtham Kruetreepradit, in Catalano's book Nepenthes della Thailandia: Diario di viaggio; the description was reviewed by Alastair Robinson, with a Latin translation by Andreas Fleischmann. The holotype (Kerr 14127) was collected in 1928 at approximately 500 m elevation, in what is now Tarutao National Marine Park, Satun Province, Thailand, and is held at the Bangkok Herbarium (BK). What is now Tarutao National Marine Park, Satun Province, Thailand, at approximately 500 m elevation. The specific epithet honours the Irish physician Arthur Francis George Kerr, who made the first known herbarium collection of this species.

World Checklist of Vascular Plants (WCVP), via Plants of the World Online (POWO), Royal Botanic Gardens, Kew.