Pitcher plant  (Nepenthes edwardsiana)

Nepenthes edwardsiana is classified as Vulnerable (VU) on the IUCN Red List (1) and listed on Appendix II of CITES (3).

This impressive species of carnivorous plant has some of the largest pitchers of all the Nepenthes species. Nepenthes edwardsiana is a vine, with modified pitcher-shaped leaves that hang from coiled tendrils (4). The pitchers of Nepenthes edwardsiana are bulbous at the base and cylindrical at the top and are an unusual red-brown in colour (2). The pitchers contain an acidic fluid, secreted by the many glands which cover the inside surface of the lower half of the pitcher (4). The smooth and waxy upper inner surface of the pitcher makes it impossible for insects that fall into the pitchers to gain a foothold (4), and a ridge of hardened tissue lining the mouth of the pitcher, the peristome, bears downward-pointing teeth, also preventing insects from escaping. The peristome of Nepenthes edwardsiana is the most highly developed and distinct of this genus (2). A lid overhangs the mouth of the pitcher, preventing rain water from diluting the pitcher fluid (2). Inconspicuous, very short hairs may cover most of the plant (2).

Endemic to Mount Kinabalu and Mount Tambuyukon in the Malaysian region of Borneo. Nepenthes edwardsiana is found growing at altitudes between 1,500 and 2,700 metres (2).

Nepenthes edwardsiana grows in mossy montane forest, amongst ridge-top vegetation either as an epiphyte or terrestrially amongst moss (2).

Pitcher plants are dioecious, meaning that male and female flowers grow on separate plants (4), and many only begin to flower once the upper pitchers are produced (5). The flowers produce larger amounts of nectar during the early evening and night. This nectar attracts a variety of pollinating insects during the day, including day moths and flies, as well as moths at night. Once fertilised, a fruit usually takes about three months to develop and ripen. The fruits of Nepenthes species produce between 50 and 500 very light, winged seeds, which can measure up to 30 millimetres long, and are thought to be dispersed by the wind (2) (6). Despite enormous numbers of seeds being produced, only a few manage to germinate and only a fraction of those survive to maturity (2).

Nepenthes species are threatened by a combination of over-collection and habitat loss (2). The biodiversity of Malaysia and Indonesia is significantly threatened by widespread habitat destruction, caused by illegal and commercial logging and large agricultural projects such as rubber and oil palm plantations (7). Nepenthes edwardsiana has a highly localised distribution making this species particularly susceptible to extinction if habitats are disturbed or there are catastrophic environmental events, such as drought or fire. For example, the El Niño event of 1997 and 1998 severely affected the Nepenthes species growing on Mount Kinabalu. A dry period depleted natural populations and a large number of forest fires broke out. In addition, montane species, such as Nepenthes edwardsiana, take longer to recover than lowland plants after such events, as growth is slower (2).

Nepenthes edwardsiana is found growing in Kinabalu National Park. The region’s protected status, along with the inaccessibility of many areas, offers this species some degree of protection, particularly from collectors. Nepenthes edwardsiana is listed under Appendix II of the Convention on International Trade in Endangered Species (CITES), limiting the international export of this species (3). However, trade is very difficult to regulate and there is no requirement for internationally traded Nepenthes to be identified down to species level. Plants simply labelled as Nepenthes accounted for 94 percent of all exported Nepenthes plants between 1988 and 1993. This needs to be remedied and urgent attention is required to close other trade loopholes (2). Nepenthes edwardsiana is difficult to cultivate (8), but increasing cultivated plant numbers should help to reduce the impact on wild populations. Artificial propagation, together with the establishment of habitat reserves and the implementation and the enforcement of protective legislation would go a long way to securing the future of this impressive species (9).

For more information on Nepenthes species see:

• McPherson, S.R. (2009) Pitcher Plants of the Old World. Redfern Natural History Productions Ltd., Poole.
• Clarke, C (1997) Nepenthes of Borneo. Natural History Publications, Kota Kinabalu, Malaysia.