Winter Carnivore Cleanups – Nepenthes hemsleyana

Since things are a bit slow at the gallery due to the end of the growing season, now is a perfect time to discuss winter carnivore cleanups. This time, the subject is one that keeps coming up concerning Nepenthes pitcher plants: “My pitcher plant stopped producing pitchers.” 90 percent of the time, the factor causing a lack of pitcher growth is a lack of humidity: studies in the last decade confirmed that once average relative humidity stays below 50 percent, Nepenthes plants stop producing pitchers. This is because on average, Nepenthes roots are to keep the plant in the ground (if you want to get a good idea of what a Nepenthes root clump looks like without digging up one yourself, just clean your shower drain one of these days), and half of the plant’s moisture requirements come from moisture (rain, fog, mist) absorbed through its leaves. Every once in a while, though, you get an exception, and we have a humdinger of one.

Regulars may recognize the enclosure Bat God from the end of 2020, containing the only Nepenthes hemsleyana I’ve ever had the privilege of viewing. N. hemsleyana is famous for being a non-carnivorous carnivore: instead of catching insects or other animal prey, this species specializes in producing traps that act as the roosting site for one of the smallest bats in Asia, Kerivoula hardwickii. In return for a safe haven, the bats provide nitrogen not just in guano, as commonly reported, but also in shed fur as the bats groom themselves and each other. (As organic gardeners will tell you, hair and fur make a great slow-release nitrogen source, and I’m currently conducting experiments with using shed cat fur as a possible alternative to guano for some Nepenthes species. Expect results later this year.) Between these two nitrogen sources, N. hemsleyana no longer produces digestive enzymes by the time it produces its distinctive upper traps, nor do the peristomes on the pitchers fluoresce under ultraviolet light as with close cousins such as N. rafflesiana.

The problem with telling people about these distinctive pitchers, though, is getting the pitchers in the first place. This original hemsleyana grew impressive pitchers in a smaller, much more compact enclosure, but upon moving it to a new location, it enthusiastically grew but didn’t produce a single pitcher. This recalcitrance isn’t due to a lack of humidity thanks to an ultrasonic fogger, and regular foliar feedings with dilute carnivore-safe fertilizer produces lots of new leaves. The problem is that while the leaves produce long ribs with the nubs of pitchers at the end, those nubs never go any further. Obviously, something is up.

Apparently the plant felt the same way, because in addition to its main vine threatening to apply for admission to the United Nations, this Nepenthes is producing a new shoot near its base. This started about three weeks ago, and the first leaves came in nice and broad. The real joy, though, is the new lower pitcher forming off the shoot’s third leaf, and new leaves coming in that appear to be just as determined. In about three weeks, we’ll know for sure if this is going to turn into a true pitcher, but the indications are good.

“This is all fine and good,” you say, “but what does that mean?” Well, it means that Nepenthes and roses have a bit more in common than you might think. Just as how roses may need to have their canes cut back to encourage new growth likely to produce flowers, sometimes a fussy Nepenthes needs to be cut back to encourage new pitcher growth. Once the pitcher on the new offshoot is established and open,, which may happen within the next week, the rest of the vine upstem from the shoot gets cut off and then cut into segments. Those segments then get a good bath in rooting hormone and then planted in a high-humidity, high-light environment to encourage new root growth. The odds are pretty good that if the cuttings take, any new growth on them will contain full pitcher development, meaning that the gallery may be overloaded with N. hemsleyana enclosures before too long. Maybe the next one needs to take a note from the bat fossil beds at Riversleigh World Heritage Site in Queensland, Australia and be entitled “Stately Wayne Manor.”