N. nebularum in cultivation at Exotica Plants.

N. nebularum has now been in cultivation at Exotica Plants for five years from seed and what we have observed is as follows.
These plants have now matured with some flowering for the second time and others for the first. The growth, flowers and habit are certainly different from any other Nepenthes sp. we have grown or seen. While they are definitely related to N. truncata they are unique and very different from this species. At times they remind us of N. veitchii,  especially the intermediate/highland form, with their hairiness, epiphytic nature and compact growth habit. Also they remind us of N. clipeata by their plant coloration and growth habit. Their cultivation requirements could be termed intermediate to highland and they will grow happily in cold temperatures unlike N. truncata and N. x robcantleyi f2. You could say that they are like a highland N. truncata and similar to the plant known as N. truncata – red leaf, highland. They do not like lowland temperatures and will regress and die. They seem to grow well in both our media of Sphagnum moss or coir chip similar to most of our Nepenthes species and hybrid plants.
On the topic of growth habit, what has become evident as the plants of N. nebularum mature is the way they have evolved or adapted their growth to secure them in their epiphytic habitat. It appears that, although the new leaf emerges from the petiole sheath of the previous leaf, as is typical of petiolate leaved Nepenthes spp., their leaf morphology is such that as the new leaves are forming the petiole grows backwards but finishes at a steep angle of around 45 degrees. This is a notable difference as  N. truncata and N. x robcantleyi, for example, curve sharply at the leaf attachment to the stem, continue growing backwards and downwards finishing horizontal or just below it. Meanwhile the tendril and leaf blade of N. nebularum are unfurling and the tendril continues to grow outwards and then the midrib starts to curve directing the tendril down and back towards the stem of the plant ‘looking’ for a branch or the like to clamp onto or grow against to secure the plant (Fig. 1, below). The tendril having found something to grow against, tightly grows and forms onto and around what it has found. Once the tendril is ‘anchored’, the midrib curves more and hardens, and finishes similar to a claw holding something. The pitcher then grows as the tendril hardens and any attempt to move or straighten the tendril and/or midrib would break it as it is rigid. It can therefore be seen that as the plant grows and the leaves radiate out from the stem in a broad whorl, the plant would anchor itself firmly in its epiphytic niche. As the plant keeps growing and produces more leaves from the growing tip the previous leaves are pushed down and the sharp angle of the petiole to the stem diminishes appearing more like the growth of N. truncata and N. x robcantleyi etc. However, although this is notable whilst observing the plant in a pot in cultivation, in its habitat other plants and mosses would also be growing with it and the leaves would be fixed in place unless disturbed.
Fig. 2, below, demonstrates this, as it can be seen how the pitcher has formed against the bench. Fig. 3, below, shows N. nebularum in habitat with its tendril formed around the branch beside the pitcher. Fig. 4, below, also shows the curved mid-rib and shaped tendril of N. nebularum in habitat on a different mountain, albeit disturbed. Fig. 5, below, is another plant in cultivation showing how the midrib has curved, pulling the tendril against the pot and now the pitcher is forming. Fig. 6, below,  is showing a seedling exhibiting this characteristic. Fig. 7 is showing the pitcher bud tight against the pot and growing. Fig. 8 shows a seedling of N. nebularum from a different mountain displaying this same characteristic although I think that the pitcher has hit the sphagnum moss and won’t reach the pot.

Fig. 9 N. nebularum in habitat on a second mountain, 
showing the tendril forming around a branch.

When this unique characteristic is compared to N. truncata, N. x robcantleyi, N. x robcantleyi f2 and N. truncata – red leaf, highland, the contrasting differences are obvious. N. truncata, N. x robcantleyi and N. truncata – red leaf exhibit slightly curved midribs with the tendrils extending out and down at an angle below horizontal to around a 90 degree angle from the leaf tip, not curling back, until it hits the ground or similar and the pitcher grows from there. This seems to suit the terrestrial habitat. N. truncata is known to grow as an opportunistic epiphyte at times but does not appear to be adapted to this habitat. N. x robcantleyi has not been discovered in the wild although its alleged female parent was growing terrestrially. Little is know about the origins of N. truncata – red leaf but its growth habit seems to be very similar to N. truncata. N. x robcantleyi f2 plants, as with their other characteristics, vary over the range of the progeny and, as was predicted in my co-authored previous paper, show characteristics which are in between N. truncata and N. nebularum as is seen in hybrids. This is evident when the plants are compared to N. nebularum and it can be seen that some of the plants are typical of N. truncata in this characteristic and some are more like N. nebularum. In a recent post on our Facebook page discussing N. nebularum, a grower posted photos of many small to medium plants of N. x robcantleyi f2 growing at the Borneo Exotics nursery and these plants are clearly demonstrating this characteristic similar to N. truncata.

The next unique characteristic is the unusual flowering of N. nebularum.
When I first saw the flowers of this species I thought that they were deformed and cut them off. Both male and female flower spikes (peduncle) emerge very small and immature (Fig.16 and 17). As they are developing and from what we have seen they remain enclosed in the petiole wings even though the new leaf has emerged and is developing (Fig. 16). Once the spike has emerged it keeps growing and matures as normally seen in Nepenthes spp. The unusual part of this flowering habit is that N. truncata, N. x robcantleyi and N. truncata – red leaf, highland and most other Nepenthes spp. flower with both the new leaf and the flower spike enclosed together in the petiole wings of the previous leaf and emerge on the same parallel plane, not twisted over and miniature as seen in N. nebularum. Again, the N. x robcantleyi f2 plants show flowering characteristics halfway between N. truncata and N. nebularum.

Fig. 16 Emerging flower spikes of N. nebularum.
Fig. 17 N. nebularum flower spike
Fig. 18 N. truncata flower emerging.
Fig. 19 Emerging flower spike of N. x robcantleyi – Borneo Exotics
Fig. 20 Emerging flower spike of N. x robcantleyi f2 – F. Mey

This then leads to the flower heads of N. nebularum which are also noticeably different to N. truncata,  N. truncata – red leaf,  N. x robcantleyi and N. x robcantleyi f2. Both the size and shape of the N. nebularum flower heads differ to all the others where the other four species and hybrids are akin to N. truncata. See pictures below.

Fig. 21 Female flower heads of N. nebularum (leftand N. truncata.

Fig. 22 Male flower heads of N. nebularum (leftand N. truncata.

Figures 23 – 27, below, are a series of comparative photos of the flower spikes of N. nebularum, N. truncata, N. x robcantleyi f2 and N. x robcantleyi. The contrasting differences are obvious.

Fig. 23
The diminutive seed head of N. nebularum (left) compared to the massive one of N. truncata.

Fig 24. The 40cm female flower spike of N. nebularum (left) compared to a 150+cm spike which is typical of N. truncata.

Fig. 25 The 74cm male flower spike of N. nebularum (left) compared to a 150+cm spike which is typical of N. truncata.
Fig. 26 N. x robcantleyi f2 female flower spike – R. De Los Santos
Fig. 27 N. x robcantleyi f2 male flower spike – R. De Los Santos
N. x robcantleyi first flowering circa 2009 – Borneo Exotics

To sum up at this time.
We have seen that when a lot of growers compare Nepenthes species the most observed characteristics are, of course, the pitchers. However, as can be seen here, there are many more parts to look at when defining species’ and the details observed and noted here play a further part to the description of N. nebularum by doing just that.
Interestingly we noted in our second paper discussing the alleged hybrid beginnings of N. x robcantleyi that, could it be seen that N. nebularum was one end of a spectrum and N. truncata was the other end of the spectrum of these unique truncate leafed plants, with N. x robcantleyi falling as a separate species in between. This we dismissed as the obvious results of the crossing of two of the N. x robcantleyi plants by Borneo Exotics gave progeny that moved closer to the characteristics of N. nebularum. This can now be seen in even greater detail as the further observations of N. nebularum in cultivation have been made and detailed above. So at this time the answer is still no and from what we have observed so far it appears more strongly that N. x robcantleyi is a hybrid and one of many possible hybrid combinations which can occur randomly in nature.
Furthermore to this interesting discussion, we have recently been show a photograph taken by a well know botanist and Nepenthes taxonomist, which I am not able to display here, of what he described as N. robcantleyi (Cheek 2011) in habitat. The plant is interesting but to us it looked similar to N. truncata – red leaf from Andreas Wistuba or like N. nebularum x truncata or vice versa with N. nebularum size and N. truncata like pitchers which were purple/brown. In our opinion, the plant showed very little likeness to the holotype of N. robcantleyi (Cheek 2011) which was based on the unofficial cultivar named ‘Queen of Hearts’. The problem when observing these plants in the wild is that, at best, their origins are speculative. It would take lifetimes to know the many influences that cause a plant to develop and whether it has had hybrid origins etc. Yet, in cultivation, we can shortcut this process to just several years by controlled breeding and observations. This is exactly what we do at Exotica Plants and have done with this species, N. nebularum, as we have just sown seed of the primary cross with it and N. truncata with the reverse hybrid to follow shortly. We have also produced species seed from two of the variants and will continue with more as they flower. Therefore in a couple of years more important observations will be made.

NB. Disclaimer: As detailed above, some of the photos I have used do not belong to me. I have sought permission where I could. This is an educational article and I believe photos can be used without breaching any copyright laws in this case. If however there are any grievances please contact us at [email protected]