Pitcher plant  (Nepenthes rajah)

Classified as Endangered on the IUCN Red List (1), and listed on Appendix I of CITES (3).

Nepenthes rajah is the most impressive, and possibly the best known of the pitcher plants. Some of the leaves become modified as they grow, developing enormous flasks known as 'pitchers'. These containers rest on the ground, and the lower pitchers may reach up to 35 centimetres high and 18 centimetres wide; the edge of the mouth has a highly distinctive wavy lip, and the outside of the pitcher is purple whist the inside is more yellowish in colour (2). The lid of the pitcher is very large and arched above the flask (2). The thick stem grows along the ground and may reach up to six metres in length. The leaves also reach a large size; they are leathery with a wavy outer margin (2). Flowers are born on a branched inflorescence (or flower stem); they have a strong sugar smell and are brownish-yellow in colour (2).

This pitcher plant is known only from Mount Kinabalu and Mount Tamboyukon in Sabah, on the island of Borneo (1).

Found in open grassy areas where the soil is loose, such as landslip areas or ridge tops, at a height of between 1,500 and 2,600 metres above sea level (2).

Nepenthes rajah is a carnivorous plant, which flowers all year round; the enormous pitchers can hold up to one litre of fluid (2). Insects are attracted to the plants by a fragrant odour but the waxy surface of the inside of the pitcher does not provide support, and the plant’s victims tumble into the fluid below. A powerful digestive acid is then released from the pitcher walls, which consumes the prey. The gigantic pitcher of Nepenthes rajah is said to capture rats, frogs and lizards as well as insects (2).

As fascinating and unusual plants, Nepenthes spp. have been collected from the wild for centuries, and there has been an increase in this demand since the late 1970s (2). Habitat loss is probably the biggest threat to their survival however, as vast areas of South East Asia are developed in order to support the growing population (2).

Nepenthes rajah is listed on Appendix I of the Convention on International Trade in Endangered Species (CITES), which bans all trade in wild plants of this species (3). It is unlikely that illegal collection poses much of a risk to the species due to the inaccessibility of its mountain habitat (2). In addition, recent micropropagation techniques have proved successful, allowing these pitcher plants to be produced artificially, thus reducing the need for wild-collected plants to meet the demand (2). This species of pitcher plant is found almost entirely within the conservation area of Kinabalu Park in Sabah, where this giant of the plant world attracts valuable tourist revenue, and this alone may well be enough to secure its future.

For more information on pitcher plants in Borneo see:

• Clarke, C. (1997) Nepenthes of Borneo. Natural History Publications, Borneo.