Nepenthes Rajah

N. Rajah is the king of the Nepenthes genus! This species produces some of the largest pitchers of any species.  

Above: N. Rajah on the summit of Mt. Tambuyukon (2500m)

A bit of backstory on the species cultivation:

This species was discovered in the 1850s, and was colloquially named "Rajah", which means king in Sanskrit title. Early on, collected plants ultimately ended up in several Victorian greenhouses throughout Europe. Nearly all of these plants died as a result of fuel shortages during WW1. The species would remain mostly uncultivated until the early 1990s, when Thomas Alt, a retired police officer from Germany, collected seeds from Mt. Kinabalu. These seeds were placed into tissue culture, which resulted in four distinct clones. Some of these clones were distributed to various botanical gardens and other plant laboratories. One of these clones was sent to Kew Gardens in the UK, and all four clones were sent to Atlanta Botanical Gardens in the US. Ultimately, the Kew Gardens clone (an unlabeled female clone from the original four) was given to Borneo Exotics and mass propagated. As of 2018, about 40 thousand plants from this clone were exported around the world. 

While this was a great benefit for the species, it also had an adverse consequence; nearly all N. Rajah in cultivation are female. Fortunately, Thomas Alt continued to sell his clones to other growers.  In addition, Andreas Wistuba and Uwe Westphal produced N. Rajah en-vitro, allowing different clones to enter the market. Since the species officially re-entered cultivation, growers such as Jeff Shafer and Jeremiah Harris have been able to flower both sexes and produce many more N. Rajah. 

Like N. Edwardsiana, N. Rajah grows on Mt. Kinabalu and Mt. Tambuyukon. Unfortunately, despite the CITES I protection, this species is still widely poached. The Tambuyukon population had some evidence of poaching, but not nearly as severe as the N. Edwardsiana population. I suspect most of the N. Rajah poaching occurs on Mt. Kinabalu, where the N. Rajah are more accessible. 

Some interesting details of this species: The N. Rajah that grow on Mt. Tambuyukon are supposedly more hairy than the Kinabalu populations. I've never been able to confirm this as I've only seen the Mt. Tambuyukon population, but the developing pitchers did indeed have some visible hairs! This species also grows sympatrically alongside N. Edwardsiana.  I observed several flowering N. Rajah growing about 5 feet away from N. Edwardsiana on Mt. Tambuyukon at about 2100m. The natural hybrid, N. Rajah x Edwardsiana, has not been directly observed in-situ but has been produced atleast twice from wild collected seeds. 

Cultivation Requirements

There are really three core tenants for successful N. Rajah cultivation: lots of room, lots of food, and lots of light! 

 

Fertilizer

Even at a young age, N. Rajah can withstand large amounts of fertilizer. Once the pitchers reach about 1-2 inches tall, I start by feeding the plant small 180 day timed release nutricote pellets in each pitcher. Unlike other species, I have not observed pitcher die-off resulting from overfeeding of nutricote pellets. Some of my younger N. Rajah even have pitchers nearly half full of dead ants! Like N. Attenboroughii, some growers report positive results by placing nutricote pellets on the soil. I have not attempted this, but I am currently running some experiments and will update this page if the N. Rajah respond positively to this fertilizer method. 

 

Light

N. Rajah grows in full sunlight in situ, without any plants providing shade. Every seedling I observed on Mt. Tambuyukon was growing in an exposed area. This is quite different from Mt. Victoria, where the N. Attenboroughii seedlings generally start growing in shady conditions before they emerge from the bonsai forest. I noticed several N. Rajah on Mt. Tambuyukon that were growing in slightly shady conditions. The plants looked terrible and did not have any developing pitchers (a sign of light deprivation). While these shady conditions were perfect for N. Edwardsiana, it was quite obvious that N. Rajah were not doing well. 

 

Soil

Over the years, N. Rajah has been cultivated sucessfully in a wide variety of soil mixes. Growers have been able to grow Rajah in pure sphagnum moss, coco chips, pumice, akadama...etc. The species does not appear to have a particular preference regarding soil choices. On Mt. Tambuyukon, I observed several seedlings growing ephytically. There was also a large N. Rajah growing on a decomposed log near the N. Villosa habitat. Despite these findings, it's worth noting that most N. Rajah in the wild grow directly in the ultramafic rock. A mixture I've used with good success is 1/3 coco chips, 1/3 akadama and 1/3 pumice. 

N. Rajah seedlings growing ephytically on a stunted tree, Mt Tambuyukon 2300m

The most important factor in the soil choice is ensuring good drainage. Several years ago, I had two N. Rajah potted in pure akadama. Unfortunately the akadama degraded over time, and both N. Rajah developed root rot and died as a result. The grower Tom Kahl advised me that pure pumice works as a good alternative. Tom has been growing dozens of N. Rajah successfully for over 30 years. Pumice takes decades to break down and drains well. The only downside to pumice is that it drains so well that a large pot is required. As an experiment, I repotted some of my N. Rajah into pumice. They continue to grow well!

N. Rajah putted in pure pumice

 

Temperature

N. Rajah does best in highland conditions, with temperatures dropping into the 50s at night and daytime temperatures in the high 70s to low 80s. There has been some speculation over the years that because the altitude distribution listed on wikipedia for this species starts at 1500m, it might be able to handle intermediate conditions. However, I suspect most of the N. Rajah growing at this low elevation were removed from higher elevations and purposefully planted near the Kinabalu nature trails. The N. Rajah growing at the Mountain Garden (Kinabalu HQ, 1560m) don't look too healthy which I suspect is because nighttime temperatures are not low enough at the park headquarters. 

Final Thoughts

This species grows very large; any grower looking to purchase one should be aware of this and have enough space prepared! Within a few years, a relatively small Rajah will exceed 1' diameter if fed and cared for well. This species, like N. Edwardsiana, often attracts growers who are allured by the photos of mature pitchers. Before purchasing this species, I strongly recommend growers first prepare a suitable grow space.