From my experience, growing Nepenthes (and other plants) indoors successfully requires an understanding of the following key metrics, from most important to least important:
#1 Light
Light meters are great tools!
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Plants obtain their energy through photosynthesis, even if they have meaty appetites! Insects for carnivorous plants are more like multivitamins - they provide the nutrients they need to build structures, but without the real fuel from photosynthesis, they can't build anything at all. If your plants are not pitchering, low light and humidity are likely culprits. |
I find that my Nepenthes thrive between 100-200 PPFD, short and fancy for the amount of photosynthetically active light available to the plant. Not all "bright light" that we mere humans see is actually useful to the plant! White light is made up of many different colors, or wavelengths, of light that normally "cancel" each other out to appear white. When white light encounters a refracting surface (like a drop of water or a prism) it breaks into the beautiful colors of the rainbow. There are also a lot of other photosynthetically active wavelengths of light (known as PAR) that we can't see in the visible spectrum, as shown in this great diagram.
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Since our eyes only perceive a narrow range of visible light, we can be tricked into thinking light is better or worse for plants than it actually is. You need to use a light meter to figure out if the available light is actually photosynthetically usable or not.
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Diagram by Fluence
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Figuring out light sounds complicated but it's actually really simple:
1) Get a light meter. The apps on your phone are really poor at detecting accurate levels of light. Really accurate light meters are extremely expensive, but luckily Nepenthes are very forgiving plants and you can get away with a moderately priced one. Mine was about $30 and worth it!
2) Measure light. Uncover the light sensor, place light AT THE HEIGHT OF YOUR PLANT LEAVES, and turn it on. Light intensity decays drastically the further away you are from the light source, so it is critically important that you measure light right at the level of your plants, otherwise your reading is useless! Lux and footcandles are basically the same thing - they both measure the total intensity of the light, but lux is metric and footcandles are, well, feet.
3) Convert lux to PPFD. Remember that not all wavelengths of light are photosynthetically active, which means light can look bright but actually be very poor at transferring useful energy to your plant. I use this handy Lux to PPFD calculator by Waveform Lighting to convert lux to PPFD. All you need to do is enter the Lux reading and the color of the light you are measuring. For example, if I am measuring my terrarium, I would input the lux reading AND the color of my lights, which is 4000K. You can usually find the color of your lights on the product page information page. If I am measuring the light on my south facing windowsill, I would input the lux reading AND Daylight (full spectrum lighting, contains all wavelengths from the sun).
Carnivero has an excellent page dedicated to the minimum and maximum PPFD levels for each genus. They find that Nepenthes can handle between 40 and 450 PPFD of light. I find my Nepenthes are happiest indoors around the low /middle of the range, between 100-200 PPFD. Happy plants pitcher profusely, have a tinge of red blush on the leaves, and good leaf-to-pitcher ratios. Too much light and they start to show signs of light stress (small, sunburned leaves, curiously due to endogenous viral activation) and too little light they will fail to pitcher. Carnivero also has a wonderful write up on the Nepenthes Light Response which goes into all of this in much more detail. A great read - thanks Carnivero!
1) Get a light meter. The apps on your phone are really poor at detecting accurate levels of light. Really accurate light meters are extremely expensive, but luckily Nepenthes are very forgiving plants and you can get away with a moderately priced one. Mine was about $30 and worth it!
2) Measure light. Uncover the light sensor, place light AT THE HEIGHT OF YOUR PLANT LEAVES, and turn it on. Light intensity decays drastically the further away you are from the light source, so it is critically important that you measure light right at the level of your plants, otherwise your reading is useless! Lux and footcandles are basically the same thing - they both measure the total intensity of the light, but lux is metric and footcandles are, well, feet.
3) Convert lux to PPFD. Remember that not all wavelengths of light are photosynthetically active, which means light can look bright but actually be very poor at transferring useful energy to your plant. I use this handy Lux to PPFD calculator by Waveform Lighting to convert lux to PPFD. All you need to do is enter the Lux reading and the color of the light you are measuring. For example, if I am measuring my terrarium, I would input the lux reading AND the color of my lights, which is 4000K. You can usually find the color of your lights on the product page information page. If I am measuring the light on my south facing windowsill, I would input the lux reading AND Daylight (full spectrum lighting, contains all wavelengths from the sun).
Carnivero has an excellent page dedicated to the minimum and maximum PPFD levels for each genus. They find that Nepenthes can handle between 40 and 450 PPFD of light. I find my Nepenthes are happiest indoors around the low /middle of the range, between 100-200 PPFD. Happy plants pitcher profusely, have a tinge of red blush on the leaves, and good leaf-to-pitcher ratios. Too much light and they start to show signs of light stress (small, sunburned leaves, curiously due to endogenous viral activation) and too little light they will fail to pitcher. Carnivero also has a wonderful write up on the Nepenthes Light Response which goes into all of this in much more detail. A great read - thanks Carnivero!
#2 Humidity
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If your plants aren't pitchering, the second likely culprit is humidity. Most Nepenthes need high relative humidity to produce their flamboyant pitchers. I am lucky to live close to the Ocean (literally a block away) and in the "fog belt" of the Northern California coast, so my indoor humidity is naturally quite high (around 50% without any interventions). To boost it further, I make "humidity trays". I fill large propagation/seedling trays with about an inch of black lava rock (far cheaper by the big bag!) and simply place the pots on the rocks. The trays catch the overflow from regular watering and the lava rock provides a porous surface for evaporation, increasing local humidity for the plants. This plus misting every morning and evening keeps humidity between 55-95% (depend on if it's on the windowsill or in a terrarium). Drenching at night is particularly beneficial for humidity loving plants like Nepenthes - the cool temperatures at night allow the humidity to remain at higher levels for longer periods of time, and I definitely noticed an increase in pitcher size and longevity after I started this practice. I monitor both humidity and temperature with SensorPush, which brings me to the third most important factor...
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The SensorPush app interface is very easy to use!
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#3 Temperature
SensorPush hiding among the plants...
Temperature is probably the hardest thing to control for growing indoors. For me it is the defining factor for which plants succeed or fail long-term. Since I live in the same space as my plants, I can't just crank the temperature up and down and be comfortable living with it! Most of my Nepenthes are solid lowland or intermediate growers. The few times I have tried true highland plants ended with miserable failures - they would put out several pitchers and appear fine for weeks or even months, but eventually their leaves got smaller and smaller and the overall appearance of the plant declined rapidly. I wish I had an outdoor/temperature-controlled space to grow highland Nepenthes! One day maybe :)
I use SensorPush to monitor my temperature and humidity conditions. I have one in my living room window and the other in a terrarium. I was astonished to discover that my windowsill conditions really are not that different from my terrarium conditions! However, in general the terrarium is more consistent because it is not affected by changing weather, and it also stays a little warmer for longer during the day and much higher consistent humidity overnight.
Light, temperature, and humidity are the MOST important for immediate success growing your pitcher plants and encouraging the development of those gorgeous traps. The following two components are more important for long-term success...
#4 Water
Thankfully the water in San Francisco has a low enough ppm that I can use it to water my Nepenthes without issue. Nepenthes are also more tolerant of higher ppm water for longer periods of time than other carnivorous plants, but they should still be flushed regularly with low ppm water to prevent mineral build up long-term. If your area has high TDS (total dissolved solids) out of the tap, you should water with distilled water or invest in an RO machine.
Learning how to properly water is a skill that takes time to develop. Nepenthes generally like to moist but not sopping wet at all times. I gently lift the pot and it if "feels light", I water until it exits the drainage holes at the bottom of the pot. Frequency in watering will vary depending on the environmental conditions and the individual needs of the plant. Nepenthes throw HUGE fits if they dry out too much - a bone dry Nepenthes will immediately drop all its pitchers and take months to recover. One of my dear friends forgot to water my windowsill plants while we were away for 3 weeks and some of my favorite Nepenthes were shriveled back to almost nothing when we came back. I was able to resuscitate nearly all the plants by watering them lightly, placing them in a plastic bag, misting heavily, then tying the bag completely so the plants were bathed in 100% humidity. It took many months but they did resume growth and pitchering! On the other hand, Nepenthes that are kept too wet for too long will rot out and die incredibly quickly. Aim for a happy median and the plants should be fine!
Learning how to properly water is a skill that takes time to develop. Nepenthes generally like to moist but not sopping wet at all times. I gently lift the pot and it if "feels light", I water until it exits the drainage holes at the bottom of the pot. Frequency in watering will vary depending on the environmental conditions and the individual needs of the plant. Nepenthes throw HUGE fits if they dry out too much - a bone dry Nepenthes will immediately drop all its pitchers and take months to recover. One of my dear friends forgot to water my windowsill plants while we were away for 3 weeks and some of my favorite Nepenthes were shriveled back to almost nothing when we came back. I was able to resuscitate nearly all the plants by watering them lightly, placing them in a plastic bag, misting heavily, then tying the bag completely so the plants were bathed in 100% humidity. It took many months but they did resume growth and pitchering! On the other hand, Nepenthes that are kept too wet for too long will rot out and die incredibly quickly. Aim for a happy median and the plants should be fine!
#5 Soil (Potting Media or Mix) and Repotting
The one big rule to follow for Nepenthes potting mixes is that whatever you use, it should be light and airy. Nepenthes are incredibly tolerant of a wide range of mixes and can thrive in anything from 100% long fiber sphagnum moss to coco husk chunks to completely inorganic clay balls! Which mix works best for you will also depend heavily on the above 4 key factors (light, humidity, temperature, and water) in your particular growing conditions. I have experimented with several mixes and I find that 50% perlite and 50% long fiber sphagnum moss in solid plastic pots works well for me. It holds enough moisture to hold the plants over for a week when I get really busy with work, but also prevents compaction over the long-term. 100% long fibered sphagnum gets too slimy for me too quickly and adding coco husk chips made the mix dry out too fast for my crazy schedule. Again, the right mix will depend heavily on your own environmental conditions - I encourage taking notes!
I generally repot Nepenthes every 2 years or any time it outgrows its current pot. You will be able to easily tell if a plant needs repotting because it has outgrown its pot if it seems like you need to water the plant all the time! I write the month and year on the back of the tag so I can remember which plants need to have their media refreshed. The media should ALWAYS be fast draining and the surface should smell fresh, not sour. If the surface appears very compact or feels slimy, and water pools or drains slowly, then it's definitely time to repot!
I'm slowly adding live sphagnum moss as a top dressing to all of my Nepenthes. I just really like the look - don't think the plants care too much either way though. I carefully pull live sphagnum growing tips from one plant and then use small forceps to carefully push the base of the moss strand into the media, leaving the top growing point just above the surface of the media. Nearly all of the moss I have transplanted in this way has survived and thrived!
I generally repot Nepenthes every 2 years or any time it outgrows its current pot. You will be able to easily tell if a plant needs repotting because it has outgrown its pot if it seems like you need to water the plant all the time! I write the month and year on the back of the tag so I can remember which plants need to have their media refreshed. The media should ALWAYS be fast draining and the surface should smell fresh, not sour. If the surface appears very compact or feels slimy, and water pools or drains slowly, then it's definitely time to repot!
I'm slowly adding live sphagnum moss as a top dressing to all of my Nepenthes. I just really like the look - don't think the plants care too much either way though. I carefully pull live sphagnum growing tips from one plant and then use small forceps to carefully push the base of the moss strand into the media, leaving the top growing point just above the surface of the media. Nearly all of the moss I have transplanted in this way has survived and thrived!