When Nepenthes become long, climbing vines they may need to be cut back. This is especially necessary if you're growing them in confined spaces like terrariums or small glasshouses. Once Nepenthes get into their vining stage, they can grow quickly and take over the place! Cutting back Nepenthes is not harmful to the plant and actually brings on the production of "lower" pitchers which in some species are the most attractive and largest. Another benefit from cuttings is you get an exact duplicate of your plant that can be insurance if your mother plant becomes ill and dies.
There are several ways of taking cuttings. I will explain what works best for me. Other vendors do cuttings differently that is conducive to their growing environment. Also, not all Nepenthes respond the same to taking cuttings. Some species and hybrids readily root from cuttings, while others can be 50-50 or worse. So don't be bummed out if you take a few cuttings and some turn black and rot out. That happens!
1. When I take my cuttings, I first choose a plant that is in the vining stage and almost always has a basal shoot or two. This way the plant will put energy into the basals in case the main growing vine dies. Also, I like vines that are green. I never cut from the woody brown stem.
2. I count 3 nodes and make my cut. In some species like N. ventricosa where the leaves are very "compact" and close together, I'll count about 5 nodes. It's better to have too much stem than too little! So err on the side of too many nodes. If you have a long vine, you can make one cut and then proceed to cut your vine into 3 node lengths or whatever you desire.
3. After making my cuts, I then cut off the bottom leaf of the stem or cut it in half. Sometimes I leave the top two leaves and / or growing tip intact. I do snip off the growing tendrils so the cutting doesn't put energy into pitcher production. Other times I'll cut the top leaves in half to make room inside baggies if the cuttings are especially large.
4. Here's where I can go 2 different ways of rooting: I fill a glass with good quality water like reverse osmosis, rain, or distilled water, and put the cuttings in that glass of water. Usually no more than 3 cuttings (depending on size) to a glass. Keep glass filled with water so that the stems are completely covered. I then place the glass near a well lit window to receive diffused lighting. I'll replace the water in the glass once a week more or less. Another way, and a more COMMON way is to prepare the cuttings as mentioned above. Some growers will use a fungicide and / or a rooting hormone like "Rootone" on the end of the cutting. Take a small plastic pot and fill it with your growing medium. Usually sphagnum is good. Wet the moss and then place the cutting in the pot with the sphagnum like you would normally pot up a plant. You want at least 1 full node below the growing medium surface. I'll usually go to the next growing leaf node. Then put the pot with the cutting in a sealable plastic baggie and leave it where it will get good lighting but not too direct light. (Some growers use fluorescent growlights and do this in a nice heated chamber like a terrarium.)
5. If rooting in water, the stems usually split in about a month or so and then rootlets will appear from the bottom. A side shoot will also appear (sometimes before the rootlets appear) from one of the nodes. In the case of a tip cutting, the growing tip will just continue to grow. The same will happen if rooted in moss but you won't see the rootlets. The plant will just make progress and grow.
6. When the stem has about 5 or 6 rootlets, I plant the cutting into sphagnum moss and then grow it out. It may take another 6 months to produce a pitcher. Remember, this is if trying to root in water. If rooting in a growing medium, then you don't have to remove the cutting at all until it gets bigger and you want to pot it up in a bigger pot.
**Note of caution: If any of the cuttings start to turn black and rot out, remove them at once! They're dying and get rid of them.
As I said before, other growers may do their cuttings differently from me. I've visited greenhouses where the grower has the cuttings in pots inside their greenhouse with their other plants attempting to root them. Strike rates vary depending on the conditions and plants. Sometimes a 75% success rate is common while other plants may be less than 50%. For more information you can read Peter D'Amato's book The Savage Garden or ask your vendor how they root cuttings.