On the Cultivation of Nepenthes rajah
Jeff Shafer, author of the web site www.plantswithattitude.com
Called the king of pitcher plants, Nepenthes rajah does indeed deserve its title. It is a magnificent species, possessing pitchers which are considered to be the largest of any species in the genus, and which may easily contain more than a liter of fluid! In addition, such large vessels allow it to catch a much broader spectrum of prey than other, more minute species; for this reason, its list of victims is reputed to include rats, but this is purportedly only true during times of drought when water is scarce and the animals fall prey to the lure of moisture inside the pitchers. In any case, this exotic denizen of Borneo’s Mt. Kinabalu has been admired since the 19th century for its beauty and size, and the matter of its cultivation was, during Victorian times, considered to be the province of only the consummate gardener. The question for today’s Nepenthes horticulturist is, however: Does this stricture still hold? Am I likely to enjoy success should I pursue the cultivation of this “royal” plant? Well, I believe that with an honest effort to meet the needs of the species, and with sufficient space and time, almost anyone can savor growing this plant, if not to outright maturity, at least to a rather enjoyable size.
However, before launching into a description of the techniques I’ve used to cultivate this plant, I wish to offer the reader a few points to consider before he decides to embark upon a similar undertaking. First, please don’t try to grow this plant if you are not willing to invest sufficient time and effort to ensure it proper care! It is a living entity, and worthy of respect for that reason alone. Moreover, it is also an organism which is relatively rare in the world, even if now, due to modern tissue culture techniques, it may be had for as little as twenty dollars. Finally, even under optimal conditions, it will require a number of years to reach a reasonable size (30 cm or more), and may require up to a decade to grow to maturity. Therefore, if one is not interested in this endeavor “for the long haul”, it is probably best to try growing some of the other, more readily cultivated, marvelous species of Nepenthes which await!
Now, assuming that one has the time, interest, and space to undertake the cultivation of this plant, let’s begin to consider its needs. N. rajah is a montane species, growing at altitudes ranging from approximately 1500 to 2700 m. As such, it requires warm days, with temperatures ranging from 25 to 30 C, and cool nights, with temperatures of about 10 to 15 C. Failure to observe these requirements will almost certainly doom your plant, or at best, limit it to being a small, miserable shadow of what it could be, so please be sure that you can provide these conditions first and foremost! In addition, like all Nepenthes, this plant needs a fairly humid atmosphere at all times, with values in excess of 75% relative humidity being the norm. However, it does tolerate fluctuations in humidity, provided that the air does not become too dry. Personally, I would not subject my plants to relative humidity less than 40%, if at all possible. In addition, keep in mind that as the plant grows larger, it is necessary for it to have fairly consistent, high humidity in order to produce the large, beautiful pitchers for which it is so highly regarded. To maintain such humidity, I use a small ultrasonic humidifier in conjunction with a humidistat. This allows one to regulate the desired humidity rather carefully, and ensures that the plant’s atmosphere does not become needlessly saturated with moisture, and that one does not have to refill one’s humidifier more frequently than absolutely necessary. Such a humidifier may be commonly purchased at a drug or hardware store. A humidistat may be more difficult to find, but an online search should quickly yield a suitable source.