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Nepenthes rajah

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Nepenthes rajah
Large lower pitcher of N. rajah. Mount Kinabalu, Borneo.
Scientific classification
Kingdom:
Plantae
Division:
Magnoliophyta
Class:
Magnoliopsida
Order:
Caryophyllales
Family:
Nepenthaceae
Genus:
Nepenthes
Species:
N. rajah
Binomial name
Nepenthes rajah
Hook. f. (1859)
1. ^ Probably more accurately classified as Vulnerable (see Conservation Status).

Nepenthes rajah, one of the most famous pitcher plants, is a carnivorous plant species of the genus Nepenthes. It was named in honour of Sir James Brooke, the first White Rajah of Sarawak.[1] The specific epithet rajah means "King" in Malay and this, coupled with the impressive size of its pitchers, has meant that N. rajah is often referred to as the "King of Nepenthes".[2]

Mount Kinabalu, Borneo — natural habitat of N. rajah

The plant has a very localised distribution, being restricted to Mount Kinabalu and neighbouring Mount Tambuyukon in Sabah, Malaysian Borneo.[3] It usually grows in open, grassy clearings and on land slips and flat ridge tops, where the soil is loose and permanently moist. Although these sites can receive very high rainfall, excess water drains away quickly, preventing the soil from becoming waterlogged. The species seems to grow exclusively in serpentine soils. N. rajah has an altitudinal distribution of 1500–2650 m a.s.l.[4] and is thus considered a highland or sub-alpine plant.

N. rajah is famous for producing some of the largest pitchers in the genus—up to 35 cm high[5] and 18 cm wide, and capable of holding up to 3.5 litres of water[6] (though 200 ml is more typical).[7] The pitchers rest on the ground and are often reclined, leaning against surrounding objects for support. N. rajah has, on occasion, been documented to catch prey as large as rodents, frogs and lizards (although insects, especially ants, comprise the majority of prey in both aerial and terrestrial pitchers).[7] Both Phillipps & Lamb (1996) and St. John (1862) observed drowned rats in a large pitcher of this species.[8] Sir Joseph Hooker, who had earlier named Nepenthes rajah, described it as "one of the most striking vegetable productions hither-to discovered".[9]

Plant characteristics

Main article: Botanical Description of Nepenthes rajah
Wikisource has original text related to this article:
Modified leaf: lamina, tendril and pitcher
Characteristic peltate leaf attachment of N. rajah
Terrestrial pitcher showing flared peristome
Flowering plant of N. rajah

N. rajah, like virtually all Nepenthes species, is a scrambling vine. The stem usually grows along the ground, but will attempt to climb whenever it comes into contact with an object that can support it. The stem is relatively thick (≤30 mm) and may reach up to 6 m in length (although it rarely exceeds 3 m).[10] N. rajah does not produce runners as some other species in the genus, but older plants are known to form basal offshoots.

Leaves are produced at regular intervals along the stem. They are connected to the stem by sheathed structures known as petioles. A long, narrow tendril emanates from the end of each leaf. At the tip of the tendril is a small bud which, when physiologically activated, develops into a functioning trap. Hence, the pitchers are modified leaves and not specialised flowers as if often believed. The green structure most similar to a normal leaf is specifically known as the lamina or leaf blade.

The leaves of N. rajah are very distinctive and reach a large size. They are leathery in texture with a wavy outer margin. The leaves are characteristically peltate, whereby the tendril joins the lamina on the underside, before the apex. Three to five longitudinal veins run along each side of the lamina and branching (pennate) veins run towards the margin. The lamina is oblong to lanceolate-shaped, ≤80 cm long and ≤15 cm wide. The tendrils are inserted ≤5 cm below the leaf apex and reach a length of approximately 50 cm.[11]

All Nepenthes pitchers share several basic characteristics. Traps consist of the main pitcher cup, which is covered by a lid that prevents rainwater from entering the pitcher and displacing its contents. A ring of hardened tissue around the opening of pitchers is known as the peristome. A pair of fringed wings runs down the front of every trap and these presumably serve to guide terrestrial insects into its mouth. Accordingly, the wings are greatly reduced or completely lacking in the aerial pitchers.

N. rajah produces two distinct types of pitchers. "Lower" or "terrestrial" pitchers are the most common. These are very large, richly coloured and ovoid in shape. Mature plants may produce "upper" or "aerial" pitchers, which are much smaller, funnel-shaped and usually less colourful than the lowers. The two types of traps differ significantly in structure as they are specialised for attracting and capturing different prey. Pitchers that do not fall directly into either group are known as "intermediate" pitchers.

The huge urn-shaped lower pitchers of Nepenthes rajah are unmistakable and for this reason it is easy to distinguish it from all other Bornean Nepenthes species.[12] Upper and intermediate pitchers are smaller, less brightly coloured and more conical than the lower pitchers, with the two wings being reduced to ribs. Pitchers are usually red to purple on the outside, whilst the inside surfaces are lime green to purple in colour. This gives a striking contrast to all other parts of the plant, which are yellow-green.

The edge of the peristome has a highly distinctive scalloped edge and is greatly expanded, forming an attractive red lip around the trap's mouth. A series of raised protrusions (or ribs) intersect the peristome, ending in short, sharp teeth that line its inner margin. Two fringed wings run from the tendril attachment to the lower edge of the peristome.

The huge, vaulted lid is another distinguishing characteristic of this species - it is the largest in the genus. The lid is ovate to oblong in shape and has a distinct keel running down the middle. The spur at the back of the lid is approximately 20 mm long and unbranched.[5]

N. rajah is noted for having very large nectar-secreting glands covering its pitchers. In particular, the inner surface of the pitcher is wholly glandular.[13]

N. rajah seems to flower at any time of the year. Flowers are produced in large numbers on inflorescences (flower stems) that arise from the apex of the main stem. N. rajah produces a large inflorescence that can be up to ≤80 cm long.[5] The individual flowers of N. rajah are produced on twin stalks (i.e. partial peduncles) and so the inflorescence is called a "raceme" (as opposed to a "panicle" for multi-flowered bunches). The flowers are reported to give off a strong sugary smell and are brownish-yellow in colour. Sepals are elliptic to oblong and ≤8 mm long.[5]

Like all Nepenthes species, N. rajah is dioecious, which means that each plant produces either male or female flowers, but never both. All parts of the plant are covered in long, white hairs when young, but mature plants are virtually glabrous (lacking hair). There seems to be little variation within the species; consequently, no forms or varieties have been described. N. rajah has no published synonyms.[4]

Known natural hybrids

Nepenthes × kinabaluensis
N. tentaculata × N. rajah

Nepenthes rajah is known to hybridise with several other species with which it is sympatric. It seems to flower at any time of year and for this reason it hybridises relatively easily. Hybrids between it and all other Nepenthes species on Mount Kinabalu (with the exception of N. lowii) have been recorded.[3]

At present, the following natural hybrids are known:

Two hybrids of N. rajah have been formally described and given specific names: N. × alisaputrana and N. × kinabaluensis.

N. × alisaputrana is named in honour of Datuk Lamri Ali, Director of Sabah Parks. It is only known from a few remote localities within Kinabalu National Park. This plant is notable for combining the best characters of both parent species, not least the size of its pitchers, which rival those of N. rajah in volume (≤35 cm high, ≤20 cm wide).[14] The other hybrids involving N. rajah do not exhibit such impressive proportions. N. × alisaputrana more closely resembles N. rajah than N. burbidgeae, but it is difficult to confuse this plant with either. However, this mistake has previously been made on at least one occasion; a pitcher illustrated in Slack (1986) as being N. rajah was in fact N. burbidgeae × N. rajah.[15]

N. × kinabaluensis is another impressive plant. The pitchers get large also, but do not compare to those of N. rajah or N. × alisaputrana. It is a well-known natural hybrid of what many consider to be the two most spectacular Nepenthes species of Borneo: N. rajah and N. villosa. N. × kinabaluensis can only be found on Mount Kinabalu (hence the name) and nearby Mount Tambuyukon, where the two parent species are sympatric.[16]

This plant was first collected near Kambarangoh by Gibbs in 1910 and later described by Macfarlane as N. sp. in 1914.[17] Although Macfarlane did not formally name the plant, he noted that "[a]ll available morphological details suggest that this is a hybrid between N. villosa and N. rajah". Kurata finally described N. × kinabaluensis in 1976 in Nepenthes of Mount Kinabalu, though the specific epithet "kinabaluensis" is a nomen nudum, as it was published with an inadequate description and lacked information on the type specimen.

Conservation status

File:Nep rajah distribution.gif
Borneo, showing distribution of N. rajah (area in red)

Nepenthes rajah is classified as Endangered (EN – B1+2e) on the IUCN Red List 2002[18] and is listed on CITES Appendix I[19], which prohibits international trade in plants collected from the wild. However, due to its popularity among collectors, many plants have been removed from the wild illegally, even though the species' distribution lies entirely within the bounds of Kinabalu Park. This led to some populations being severely depleted by over-collection in the 1970s.[20]

This being the case, however, the short-term future of N. rajah seems to be relatively secure and it would perhaps be more accurately classified as Vulnerable.[21] This agrees with the conservation status of N. rajah according to the World Conservation Monitoring Centre (WCMC), under which it is also considered Vulnerable. Although N. rajah has a restricted distribution and is often quoted as a plant in peril, it is not rare in the areas where it does grow and most populations are now off-limits to visitors and lie in remote parts of Kinabalu National Park. Additionally, the recent advent of artificial tissue culture technology in Europe and the United States has meant that plants can be produced in large numbers and sold for relatively low prices (~US$20-$30 in the case of N. rajah). This has, to a large extent, removed the incentive for collectors to travel to Sabah to collect the plant illegally, and demand for wild-collected plants has fallen considerably in recent years.[22]

The newly opened Mesilau Resort, which lies near the golf course behind the village of Kundasang, is now the only place where regular visitors can hope to see this spectacular species in its natural habitat.[23] Daily guided tours are organised to the so-called "Nepenthes Garden". Here, several dozen N. rajah plants grow near the top of a steep landslide. Both young and mature plants are present, some with sizable pitchers over 30 cm in height. Almost all other natural populations of this species occur in remote parts of Kinabalu National Park, which are off-limits to tourists.[23]

Cultivation

Nepenthes rajah has always been considered to be one of the more difficult Nepenthes species to cultivate. However, in recent years it has become apparent that the plant may not be deserving of its reputation.

Cultivated N. rajah plant

N. rajah is a montane species or "highlander", growing at altitudes ranging from 1500 to 2600 m. As such, it requires warm days, with temperatures ranging (ideally) from approximately 25 to 30 ℃[24], and cool nights, with temperatures of about 10 to 15 ℃.[24] Here, it is important to note that the temperatures themselves are not vital (when kept within reasonable limits), but rather the temperature drop itself; N. rajah needs considerably cooler nights, with a drop of 10 ℃ or more being preferable. Failure to observe this requirement will almost certainly doom the plant in the long term or, at best, limit it to being a small, unimpressive specimen.

In addition, like all Nepenthes, this plant needs a fairly humid environment to grow well. Values in the region of 75% R.H.[24] are generally considered optimal, with increased humidity at night (~90% R.H.). However, N. rajah does tolerate fluctuations in humidity, especially when young, provided that the air does not become too dry (below 50% R.H.). Humidity can be easily controlled using an ultrasonic humidifier in conjunction with a humidistat.

In its natural habitat, N. rajah grows in open areas, where it is exposed to direct sunlight - it therefore needs to be provided with a significant amount of light in cultivation as well. To meet this need, many growers have used metal halide lamps in the 500–1000 watt range, with considerable success. The plant should be situated a fair distance from the light source, 1 to 2 m is recommended.[24] Depending on location, growers can utilise natural sunlight as a source of illumination. However, this is only recommended for those living in equatorial regions, where light intensity is sufficient to satisfy the needs of the plant. A photoperiod of 12 hours is comparable to that experienced in nature.[24]

N. rajah plant with Drosera species in foreground

Pure long-fibre Sphagnum moss is an excellent potting medium, though combinations involving any of the following - peat, perlite, vermiculite, sand, lava rock, pumice, Osmunda fibre, orchid bark and horticultural charcoal - may be used with equal success. The potting medium should be well-drained and not too compacted. Moss is useful for moisture retention near the roots. The mix should be thoroughly soaked in water prior to potting the plant.

It has been noted that N. rajah produces a very extensive root system (for a Nepenthes) and, for this reason, it is recommended that a wide pot be used to allow for proper development of the root system.[24] This also eliminates the need for frequent re-potting, which can lead to transplant shock and the eventual death of the plant.[24]

Purified water should be used for watering purposes, although 'hard water' is tolerated. This is done to minimise the build-up of minerals and chemicals in the soil. Water purity greater than 100 p.p.m. of T.D.S. is often quoted as ideal.[25] A reverse osmosis unit can be used to filter the water or, alternatively, bottled distilled water can be purchased. Watering should be done regularly. However, plants should not be allowed to sit in water, as this may lead to root rot.

N. rajah is a carnivorous plant and, as such, supplements nutrients gained from the soil with captured prey (esp. insects) to alleviate deficiencies in important elements such as nitrogen, phosphorus and potassium. Just as in nature, cultivated plants' 'diet' may include insects, although this is not necessary for successful cultivation. Crickets are recommended for their size and low cost. These can be purchased online or at specialist pet stores. They can simply be dropped into the pitchers by hand or placed inside using metal tongs or similar, whether dead or alive.

From trials carried out by a commercial Nepenthes nursery[26], it appears that micronutrient solutions have "a beneficial effect on plants of improved leaf colouration, with no deleterious affects" as far as can be seen. However, it would require more research to verify these results. Actual fertilisers (containing NPK) were, on the other hand, found to "cause damage to plants, promote pathogens and have no observable benefits". Hence, the use of chemical fertilisers is usually not advised.

Above all, it should be remembered that the primary goal of any growing setup is to try to mirror the conditions the plants experience in their natural habitat as much as possible. Under optimal conditions, N. rajah can reach flowering size within 10 years of seed germination.

Common misconceptions

N. rajah growing on ultramafic soil

Nepenthes rajah has been a well-known and highly sought after species for over a century and, as a result, there are many stories woven around this plant. One such example is the famous legend that N. rajah grows exclusively in the spray zones of waterfalls, on ultramafic soils. Although the latter is true, N. rajah is certainly not found solely in the spray zones of waterfalls and this statement seems to have little basis in fact.[3]

It is likely this misconception was popularised by S. Kurata's 1976 book Nepenthes of Mount Kinabalu, in which he erroneously states that "N. rajah is rather fond of wet places like swamps or the surroundings of a waterfall".[1] With the exception of N. mirabilis, no Nepenthes species have been reliably recorded from swamps. Such claims were presumably originally the result of attempts to further increase the legendary status of the plant.

This being the case, it does appear, however, that certain N. rajah plants do in fact grow in the vicinity of waterfalls (as noted by H. Steiner, 2002) "providing quite a humid microclimate"[8], which may indeed be the source of this particular misconception.

Another myth surrounding this species is that it occasionally catches small monkeys and other large animals in its pitchers. Such tales have persisted for a very long time, but can probably be explained as rodents being mistaken for other species.[27] It is interesting to note that one common name for Nepenthes plants is 'Monkey Cups'. The name refers to the fact that monkeys have been observed drinking rainwater from these plants. Thus, in a sense, this mythology has some basis in fact.

Notes

  1. ^ a b Kurata 1976, p. 61.
  2. ^ HortiPlex Plant Database Entry for Nepenthes rajah
  3. ^ a b c Clarke 1997, p. 123.
  4. ^ a b Clarke 1997, p. 120.
  5. ^ a b c d Clarke 1997, p. 122.
  6. ^ Mount Kinabalu National Park: Subalpine Zone
  7. ^ a b Clarke 2001, p. 7.
  8. ^ a b Steiner 2002, p. 94.
  9. ^ Phillipps & Lamb 1996.
  10. ^ Clarke 1997, pp. 10, 120.
  11. ^ Clarke 1997, pp. 120, 122.
  12. ^ Clarke 2001, p. 26.
  13. ^ Danser 1928, Entry 38.
  14. ^ Clarke 2001, p. 10.
  15. ^ Clarke 1997, p. 157.
  16. ^ Clarke 1997, p. 165-167.
  17. ^ Kurata 1976, p. 64-65.
  18. ^ The IUCN List of Threatened Species: Nepenthes rajah
  19. ^ APPENDICES I AND II as adopted by the Conference of the Parties
  20. ^ Clarke 2001, p. 29.
  21. ^ Clarke 1997, pp. 170-172.
  22. ^ Clarke 1997, p. 172.
  23. ^ a b Clarke 2001, p. 38.
  24. ^ a b c d e f g On the Cultivation of Nepenthes rajah
  25. ^ D'Amato 1998, p. 7.
  26. ^ Nepenthes Cultivation and Growing Guides
  27. ^ D'Amato 1998, XV.

References

Wikispecies has information related to Nepenthes rajah.
Wikimedia Commons has media related to Nepenthes rajah.
Wikiquote has quotations related to Nepenthes rajah.
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