Grow Guide
Nepenthes
Introduction
Nepenthes is a large genus of tropical, vining carnivorous plants native primarily to mountainous regions of Southeast Asia. They are commonly known by the name Tropical Pitcher Plants, but as there are four other genera with the common name of Pitcher Plants, it can become confusing unless the scientific names are used. This genus’ impressive pitchers - suspended from the strappy leaves of the vines - are what makes them such a great collector’s plant. Indeed, the showy pitchers ranging from blood red “urns” to dainty yellow “cocktail glasses” have been capturing attention since the Victorian era when they were used as fancy houseplants. Since then, many more Nepenthes species have been discovered and introduced into cultivation with such discoveries as the fuzz covered N. diabolica and the mammoth-sized N. attenboroughii, being particularly notable. Today, these special plants have become more widely available than ever before with the use of tissue culture and horticulturally-produced seed, as well as the continual process of discovering better growing techniques.
Nepenthes seeds are usually thin, lightweight and slender, allowing for easy wind dispersion - although N. pervilleii is an exception along with a few other species. When the seeds sprout they have a pair of cotyledons; every leaf afterwards is a true leaf. During the seedling stage they produce proto-pitchers. Eventually, the plant will become large enough to start producing regular pitchers. Pitchers form at the end of the leaf’s midrib which continues past the main leaf to create a “tendril.” The tendril will continue to lengthen, either stopping growth on their own or when the end of the tendril hits an object. Then the end of the tendril swells up into the pitchers Nepenthes are known for.
At this point, the plant will be a compact rosette of leaves with pitchers encircling it at the end of the leaves’ tendrils. This compact growth is the basal phase. During this phase they produce lower pitchers. The lower pitchers typically have two wings running down the front of the pitcher which insects use as ladders to reach the pitcher’s nectar. Some Nepenthes species (rhombicaulis) further aid the insects in their quest to fall into the pitchers by burying their pitchers to some extent into nearby undergrowth, similar to a pitfall trap.
When the basal growth finally gets large enough, the stem between each new leaf lengthens and the plant switches to vining growth. During the transition between basal and vine, intermediate pitchers are produced but these give way to upper pitchers. Depending on the species, they may continue to produce mainly lower pitchers. Upper pitchers are typically smaller than lowers though there are exceptions to this, such as N. edwardsiana, which produces massive uppers compared to the lowers. The uppers are often more extreme in shape, as well, and much daintier.
Uppers can be identified by their lack of wings and the tendrils that twine into loops. The tendrils on uppers do this in order to get a handhold on nearby growth, as the vine continues growing upwards and becomes unable to support its own weight. Some species have a lower tendency to vine, and instead, live the majority of their life as a basal. When the vine or, in the case of rosette species, the basal, becomes mature enough and seasonal cues encourage the plant, they will flower either male or female and the lifecycle will continue.
Nepenthes are loosely categorized into three distinct groups, and one subgroup, based on their growing requirements and the altitude each species grows at in the wild. These groups are as follows:
Lowlanders
Prefer day temperature between 80 degrees F to 90 degrees.
Temperature drop to 65-70 degrees F.
Intermediates
Prefer day temperature between 75 degrees F to 86 degrees.
Temperature drop to 60-70 degrees F.
Highlanders
Prefer day temperature between 70 degrees F to 78 degrees.
Temperature drop to 50-60 degrees F.
Ultra-Highlanders
Prefer day temperature between 65 degrees F to 75 degrees.
Temperature drop to 45-50 degrees F.
This should only be used as a starting guide to finding what temperatures work best for the plants in one’s own growing conditions. This is because many species are adaptable and even certain clones are better with certain temperature ranges than others (more on clones in the Propagation section). In addition, not everyone’s growing area can meet these exact temperatures, yet the plants will often grow well still. Also, some of these groups, mainly ultra-highlanders and intermediates, can be grown just fine in temperature ranges suited more to other groups of Nepenthes. Ultra-highlanders are a good example of this as they are usually grown as highlanders. An important thing to remember about temperature requirements is that they are flexible in proportion to your other growing conditions as they simply allow the species specific metabolism to occur correctly and therefore the actual temp range requirements fluctuate. Generally, stresses should be minimized or countered, a case in point of this would be N. villosa - frosty cold night temps minimize the stress on the plant in cultivation as it caters to the plant's natural preferred temperature range for a correct metabolism.
The differences between these groups does not stop at ideal temperature ranges. This same categorization can be used to summarize growth rates, looks, and helps manage expectations. For instance, lowlanders are generally much faster growing than highlanders though there are exceptions to this rule, such as N. merrilliana. Intermediates are often the most adaptable and durable plants, such as the widespread hybrid, N. x ventrata. Highlanders are the most diverse group, with the most desirable species falling in this category being villosa, edwardsiana, rajah, etc. Highlanders are also the slowest growing group, overall.
Now ampullaria and bicalcarata are great species, and perhaps the most desirable of the lowlanders, but they, like many lowlanders, still aren’t as impressive as many highlanders, and have poor leaf-to-pitcher ratios. The-leaf to-pitcher ratio being the size proportion between the main leaf and pitcher; lowlanders generally have huge leaves with much smaller pitchers, and therefore, take up much-needed space compared to highlanders that have more equal leaf-to-pitcher ratios. So, the question often arises, why aren’t there more easy to grow lowlanders and intermediates that look as impressive as a N. hamata, jamban, or rajah? The answer to this is likely because highlanders grow high up in the mountains where they are isolated and forced to slowly evolve and adapt to the surrounding environment. In contrast, lowlanders grow in either lowlands, peat swamps, or the lower parts of the mountains, and their seeds can be dispersed easily from one place to the next and thus the isolation needed for speciation (the evolution of new species) is eliminated.
Soils
Due to their carnivorous habit, which evolved to supply critical nutrients to the plant - as the soils they grow in are devoid of sufficient nutrients - Nepenthes have some particular soil requirements. For this reason, they are not grown in actual soil in cultivation, instead they are grown in soilless medias, which are still referred to as soil mixes. These soilless medias can be made airy and porous which is needed for Nepenthes, since many grow as epiphytes (plants that grow on trees, but are not parasites), or on similarly airy substrates or soil such as limestone cliffs and ultramafic soils. Because of this need for a low nutrient, airy, soilless media, the soilless medias used for a different group of plants more widely grown that have similar soil requirements to Nepenthes were quickly adopted by Nepenthes growers early on in cultivation. This group of plants was, of course, Orchids, the showy flowers that usually grow as epiphytes and need light airy media. And so, it came to be that Long Fibered Sphagnum, a popular orchid media, became the mainstay of Nepenthes growing.
Orchid’s extra chunky medias such as bark did not find much use in Nepenthes, however, because unlike an orchid’s thick ropey roots, Nepenthes have fine, brittle, black roots that need a tighter soil structure. For this reason, perlite is used instead as it has a smaller particle size but adds plenty of fluff to a media mix. This combination of Sphagnum and perlite, usually recommended as equal parts of each, is generally touted as the best all-around media to use because it is lightweight, easy to use, widely available, and is more affordable than some of the alternatives. This does not make it the best choice for every Nepenthes species or hybrid though. Still, most species and hybrids can be grown well in a Sphagnum perlite mix - even the species that do not prefer it.
As for how much perlite to mix in with the Sphagnum, it depends on the size of the perlite, your watering schedule, and the individual plant’s requirements. A mix of half and half of each is a good starting point though, more or less perlite can be used. A coarse-sized perlite is generally recommended for maximum air penetration into the soilless media, especially for large robust plants, but it should be noted that finer perlite is useful and possibly even better. The smaller particle size allows better contact when rooting cuttings or repotting small Nepenthes, reduces the likelihood of large air gaps that can halt root growth, and allows for easier penetration of the roots into the growing media. Pumice is a better alternative to perlite if available.
Coconut coir chips and coir is becoming a more popular growing media component. It is affordable and lightweight when dry. However, it is often salty and has to be soaked multiple times to eliminate the worst of the salts. Borneo Exotics primarily uses coir chips in their nursery however, with great success. Root growth in coco is a noticeable improvement over Sphagnum, with the plants typically having a more robust leaf (thicker, waxier) and more coloration while Nepenthes grown in Sphagnum seem to increase leaf size more rapidly under ideal conditions and have a vibrant green coloration - however root growth is not impressive. This is the media I use primarily and recommend due to its long lasting nature, overall compatibility with most Nepenthes, and the increased root growth which is important for long term plant stability. Most issues with Nepenthes can be traced to a lack of active root growth, when the roots are not happy the plants won't be either...
Peat/perlite mixes have also been used, and still are, occasionally. However, peat seems to be more of an outdated media component for Nepenthes, as it is easily compacted and becomes waterlogged. It is good, however, for making high perlite mixes more moisture retentive and lowlanders appreciate the extra moisture.
Kanuma is a bonsai soil that are great for difficult highlanders such as the Ultramafic species (Nepenthes that grow on ultramafic or volcanic soils such as rajah, villosa, burbidgeae and palawanensis). It stimulates more root growth than Sphagnum and shortens acclimation time and establishment for ultramafic species. We recommend using it for species such as rajah, villosa, and especially attenboroughii and palawanensis. N. palawanensis grows extremely poorly in Sphagnum mixes in our experience, but thrives in a kanuma/perlite mix.
Growing conditions
Optimal growth rates are dependent on the size and quality of the root system. It is not uncommon for a plant to leaf jump (each leaf bigger than the previous) and be doing well, and then suddenly stall or shrink in size because it has become too large for its root system, which has remained the same size since it was first received. A healthy Nepenthes will always be leaf jumping until maturity - leaves being the same size or only a little bigger is a sign that something is wrong. The most vigorous species, typically lowlanders or intermediates such as N. ventricosa, produce new roots easily and quickly, which supports their quick growth above ground. Many highlanders can be stubborn to root, potentially leading to long periods of little growth. The plant should eventually acclimate, recover, and produce more root growth, at which point the leaf growth will be much faster. However, this can be a lengthy wait that can end in fatality.
Good growing conditions are important to help them establish quicker. Using the aforementioned temperature ranges and nighttime temp drops, based on which group the Nepenthes belongs to, lowlander, intermediate, or highlander, is important. Humidity can be kept high, though it can make the plants less durable and more prone to wilting if the humidity suddenly drops. Keeping the humidity extremely high is often critical for good growth on small plants. Wilting can cause severe damage if not caught and stopped early in the process. Many Nepenthes can be weaned off high humidity and grown in typical household humidity levels although the process can be lengthy, and some species do not pitcher well in low humidity. A good compromise is a humidity in the 70% range. They make thicker waxy leaves in this range, the damage won’t be so catastrophic if the humidity levels falter, the plants pitcher well, and the humidity level is easier to maintain than 80% or higher. However, for small plants a humidity dome can prove invaluable and can make some stubborn plants thrive, especially useful for BE imports...
Generally, Nepenthes grow well in much reduced light levels compared to full sun. 50% shade will often achieve good growth. Too strong lighting can cause leaf burning and poor growth. Light levels play an important role in leaf to pitcher ratios. For instance, in dimmer conditions leaves become larger while pitcher size decreases. Pitchers can also have reduced coloration. If the light is increased a bit, one will find the sweet spot, when healthy growth is produced, and pitcher size is increased. This can take some experimenting as every growing setup differs. Red leaves are not a good sign.
For watering, a low ppm (parts per million) water is ideal. Reverse osmosis, rainwater, or distilled water fits this purpose though water with up to 200 ppm is often safe to use. Some ppm is recommended, not 0 ppm. As minerals slowly build up in the soil, it is recommended to occasionally flush the growing media. Flushing is a heavy top watering meant to wash away the excess minerals. Nepenthes prefer to be kept moist but not soggy.
Propagation
There are three main ways of propagating Nepenthes: cuttings, seeds, and tissue culture. It is important to address tissue culture first, as it is the way the majority of Nepenthes today are propagated and issues in tissue culture can cause success or failure later on when the plant is grown by a grower, regardless of how ideal the growing conditions are. For this reason, myths have been circulated that tissue culture plants are always lower quality than seed grown plants or Nepenthes produced from cuttings, which is not the case. The truth is tissue culture is one of the best ways to propagate and make available the most vigorous clones of a species or hybrid. Anyone who has grown Nepenthes from seed and had a few seedlings dwarf all the other seedlings will understand why it’s good to tissue culture the most vigorous plants – they actually grow unlike other clones that stay small for ages! This way, with TC you don't have to worry about being purposely sent a runt seedling while all the vigorous seedlings were cherry picked and kept by the grower. Similarly, tissue culture allows the quick propagation of the most desirable clones, such as confirmed gender clones (since Nepenthes are either male or female) so you know if you have compatible pairs, or clones with the best coloration and shape. It also makes many Nepenthes more affordable. However, most Nepenthes tissue culture is done poorly so these benefits are reduced; more on this below.
Ideally, tissue culture should work like this: a female Nepenthes blooms and is pollinated to make a great cross. The resulting seeds are then sterilized and stuck onto a sterile, gelled, growing media in a petri dish, test tube, or other clear container. If done properly, no microbes will remain and therefore the plant culture will be free of bacteria or fungus which would eat up all the growing media in the dish, or as it’s better known in tissue culture, a “flask.” The seeds will germinate, grow because they are fed from the sugars and nutrients in the gelled media, and then will be moved to a new flask with hormones. The hormones will induce the seedlings to produce many shoots which can then be removed, grown out bigger in hormone-free media, and then be removed from tissue culture to be acclimated to typical Nepenthes growing conditions, such as a Sphagnum media, and temp drops.
When the plant is in tissue culture it cannot regulate itself like a normal Nepenthes would as it is impossible to photosynthesize in the closed sterile environment of the flask. For this reason, the plant depends heavily on the gelled tissue culture media which becomes the deciding factor in how fast the plant will grow in tissue culture and the quality of its growth. Poorly-suited tissue culture media can cause poor quality growth, in turn being hard for the plant to recover from once out of tissue culture and in normal growing conditions. Other times, a low-quality plant will form in tissue culture for no good reason and all its fellow shoots will be just fine. Either way, the occasional low-quality fluke plant will make it to the market and be sold to a grower where it will sulk for a while and either grow out of the phase or continue to deteriorate. There are certain Nepenthes known to do this more often than others which at Cross Exotics we try to avoid. Some diabolica clones for instance appear to be green algae strands rather then real plants due to the TC media not being optimal. In addition, the high hormone concentrations used often induces non beneficial mutations in the clones over time that are irreversible. Many species therefore have a terrible reputation in cultivation, but in reality non-TC plants of the same species are quite vigorous. As these mutations occur over time, clones that have been in cultivation the longest often are the most troublesome... species that have well known clone issues like this are northiana and rajah... Fortunately, the majority of tissue culture plants do not suffer from this and newer released clones (10 years old even) are often quite vigorous. TC neps are certainly better than buying somebody's dying runt seedling just cause it's seed grown.
Seeds are the most exciting way to propagate Nepenthes. As they are dioecious plants, that is each plant is either male or female and does not produce both types of flowers on one plant, it is necessary to have a blooming pair to successfully pollinate the flowers and produce viable seeds. Just like a new leaf, the inflorescence, or flower spike as it’s also known as, will emerge from the previous leaf. The inflorescence is the flowering structure or stalk where the individual flower buds are arranged. The number of individual flower buds can vary widely from just a handful of flowers to hundreds on one spike. Because the spike emerges from the previous developing leaf, it is possible to identify a spike before it emerges as its shape will be outlined in the leaf. Once emerged it is important to identify the gender of the plant if it is not already known. Sometimes this can be told right away, or one will have to wait for the spike to develop more. The flower buds of a male plant are rounded while a female plant is more oval in shape. If it is female, already saved pollen from one’s own collection can be used, or pollen can be requested from other growers. It is common practice that the grower with the female Nepenthes splits the resulting seeds equally with the pollen donor unless otherwise agreed.
If male, the individual open anthers can be cut off the spike, as the pollen matures (should be bright yellow and fluffy - about three days after opening) and then dried in the fridge to make long term storage possible. If the pollen is too moist, it will mold when stored, and become useless. The removed anthers can either be left as just the pollen ball or a paintbrush can be used to brush the pollen onto a piece of parchment, and the rest of the flower bud is discarded. A silica packet can then be used to keep the pollen dry. The pollen or pollen balls can then be put into a sealed container and refrigerated. If longer term storage is wanted, the pollen can be transferred to the freezer after around a week in the fridge and stored for up to a couple of years although not recommended.
To pollinate a female Nepenthes, it is necessary to catch each flower at the receptive stage. The buds open starting from the base up. As Nepenthes are not naturally pollinated by bees or hummingbirds, they lack the showiness of a typical flower. For instance, they lack petals. This basic flower is because Nepenthes are normally pollinated by flies and ants, and therefore, attract their pollinators with a scent that can range from slightly sweet to musty smelling. The flowers do have sepals though, which resemble small petals, at the base of each flower bud. As the spike matures, the lower buds will begin to exert a flattish “pad.” This is the stigma where the pollen is placed for successful pollination. Just because the stigma is visible does not mean it’s ready for pollination, however. The sepals will begin to bend away from the flower. Once the sepals hit a 90-degree angle, perpendicular to the stigma, they should stop bending. The flower is usually ready to be pollinated one or two days after the sepals hit this point. At this point, use a paintbrush dabbed in a small amount of pollen to apply the pollen to the sticky stigma on all the flowers that are ready. Pollination will need to be continued whenever more flower buds are receptive. For best results pollinate the flowers right before or at night or the early morning, mainly as they are more sticky at those times.
If pollination is successful, the flower buds will begin to swell up into pods. These pods will take several months to mature, and will eventually become brittle and start to crack. At this point, the pods that readily crack when lightly pressed are ready for harvest. Some crosses are more successful than others, and certain hybrids are sterile. For example, the common N. x ventrata is sterile and N. robcantleyi crosses generally have lower success rates than other crosses. This is something to keep in mind. To sow the seeds, fill a pot or several with sphagnum, and top it with an inch layer of finely milled Sphagnum. Wetting the surface and lightly packing the sphagnum will ensure good seed to Sphagnum contact without air pockets. The thin seeds can then be densely sprinkled onto the surface and spritzed with water from a spray bottle. The pot can then be placed into normal Nepenthes growing conditions, although high humidity is necessary. Bagging the pot can help maintain the humidity while they sprout.
Seed germination is sometimes quick although it can also take several months. If unable to sow immediately, seeds can be stored in a fridge for a short period of time without much reduction in germination rates. If algae becomes problematic, hydrogen peroxide at the regular concentration of 3% can be used to control the algae without harming the seedlings.
Cuttings is probably the most common way to propagate Nepenthes for most growers. When the plant vines, it will often produce one or more basals. One of the basals is usually left attached to the vine so the plant produces both upper and lower pitchers. It also makes the growth habit of the plant more pleasing to the eye. These basals can be removed by clipping them off in a clean cut, where they attach to the vine, or as near to it as possible. The basals can then be treated as cuttings. For vine cuttings, a length of nodes, from the vine’s main growth point down to whatever size the vine is to be reduced to, is chosen. This part of the vine is then lopped off and cut into sections, usually two nodes each.
These cuttings are then cleaned up using a sharp knife to make a small fresh cut at the base of the cutting under water. Similar to cutting the stump of a Christmas tree off, this cutting off the end bit of the cutting allows the cuttings to easily absorb moisture and doing it in a basin of water keeps air from clogging the cutting’s vascular system at the cut which would prevent water absorption. The leaves are often cut down to about half size, to reduce the likelihood that the leaves will evaporate more water than the cutting’s rootless base can provide; this is not required on thick leafed species like N. lowii. These cuttings can then be dipped in a rooting hormone and potted up like a normal Nepenthes in a media of the grower’s choice, with the clean cut buried.
Tbh, I think the whole clean cut under water and using hormones is a complete joke that provides no real advantage but its still good advice. For the cut just make sure to keep it moist so it doesn't callus over. What is important is that the plant is healthy and preferably from you collection so it doesn't stress out from a change in growing conditions. If a cutting randomly dies or takes forever to do anything, its probably stressed and was stressed when still uncut. There is such a thing as a bad cutting and there's not much rhyme or reason to it.
Some growers use their regular growing media while others use special medias they use exclusively for cuttings, like live sphagnum. A kanuma mix is good (best perhaps...) for quickly rooting many species, but humidity must be kept high in this case as this mix doesn’t make good contact with the cutting. It is good practice to bury one node below the soil line so that it can be kept out of harm’s way and potentially sprout up into a new growth point in case the above node is catastrophically injured. The cuttings will usually root in one to two months, though occasionally it takes longer, and a new growth point will emerge from one of the nodes.