Question
QUESTION: Hello, Chris, and happy new year!

My question is why my sundews aren't producing any more dew on their little goo-sticker appendages which grow off of the plant's leaves. My Drosera Binata, Drosera Capensis, and Drosera Capensis Alba aren't producing very much dew at all anymore.

I recently purchased and set up a 4-tube shop light and put 4 T8 fluorescent bulbs in it. The light currently resides like a foot and a quarter above the plants. Could it be that the much more intense light than what I had is drying them up? I'm starting to get worried about them. (My Venus flytraps and pitcher plants are doing well, however, and the pitcher plants are secreting a sticky substance along their pitcher rims and "spinal column" leading back down to where the plant grows out of the soil.")

Or could it be that my humidity isn't good enough or I'm watering them too much or too less? Since I bought this new light system, the soil for all of my plants seems to dry much more quickly and I find myself having to water them more frequently. The humidity in my room is around 40-45%.

They continue to grow well, but I'm worried because they aren't producing very much "dew" substance from their hairlike follicles. Thanks for your time in reading and responding to my questions!

ANSWER: Hello Devon,

The answer is... none of the above.

Actually, Sundews need a large amount of light to produce dew. The lights you bought are not intense enough to provide enough light for any of the plants you have. The only reason the Venus Flytraps are still going are the reserves of sugars they stored in their rhizomes. They too, are waiting for more light. The only problem now is that the Venus Flytraps need a dormancy period during winter or they will likely die off in the Spring this year after depleting their energy reserves completely.

What kind of Pitcher plants do you have? There are five known Genera of Pitcher plants across the globe. Some are tropical and some are temperate. If you have Sarracenias, they are temperate and will need dormancy with the Flytraps. If you have Nepenthes, they are tropical and will need to stay with the sub-tropical sundews you have.

The sundews you have are sub or also called semi tropicals that can grow year round so long as they have enough light, water and warmth. The D. capensis likes the temperature a little cooler than D. binata, but can tolerate into the low 80s if needed. They really prefer temperatures in the low to mid 70s. If they are in temperatures that are too high or too low  they will reduce their dew production.

Just keep the water level one quarter the way up the bottom of the Sundews' pots and they will be happy. Humidity has little bearing on most sundews' dew production so long as the humidity does not fluctuate greatly in a short time period.

My thinking is that the temperature right over your Sundews is higher now due to the light, thereby drying out the dew a bit. I do use florescent lights of the T-12 tube variety (40 watt) and I use a lot of them. I have a 3x4 foot area in which I have placed 6 sets of florescent lights, each with two tubes, totalling 12 tubes with 3000 lumens each. The total lumen output is in the 36000 plus range in the center of the setup with the lights about 8 inches above my Sundews. I have hundreds (yes they need repotting as they are overcrowded now) of D. adelae and D. capensis growing like a carpet in pots sitting in an inch of water. They are producing dew like crazy. My present humidity is usually about 50% and the temperature hovers between 75 and 80. The lights are on for 12 hours right now as it is winter. In the growing season I have the lights on for 16 hours a day. That just gives you an idea of what Sundews grow in. Your environment sounds about the same, but the "about" is what you need to figure out and change. If the temperature is too high, get cool white florescent tubes and install a fan or air conditioner indirectly in the room so it does not blow on, and dry out, your plants. Increase the light intensity by bringing the lights closer to the plants. The lights you have would be about 6000 total lumens for 4 20 watt tubes, so that will be barely adequate for those Sundews for winter. I would suggest a window with good sun in the morning to enhance the light intensity a bit as well.

I would suggest providing dormancy for your Venus Flytraps and finding out what kinds of Pitcher plants you have so you can determine what to do with them as well. Temperate plants that do not receive winter dormancy tend to become annuals and die off within a year as they use up all their reserves too quickly.

Christopher

---------- FOLLOW-UP ----------


Pitcher Plant   QUESTION: Well, we currently have had really cloudy conditions so there's no sun coming through my window, although there has been days where it's pretty bright.

I have a Nepenthes (Sanguinea, I believe), and 2-3 types of Sarracenia. Purpea is the one I've had the longest, and I recently got two different species from a nursery, or at least I think they are different.

My Venus flytrap's trap have gotten a very deep red. I know the light is only like half of what they need, but wouldn't they not be so crimson if they weren't getting enough light? Just wondering.

I have a picture of my two new species of pitcher plants, with the purpea in the background to the left. The new ones are the closest and in the front. I thought they were different species due to the one growing lower to the ground, and have different-shaped pitchers. The taller, skinnier ones also have white on the backside of their pitchers with red veins.

Hope my picture helps because my camera isn't very good with quality. Thanks again for your help!

ANSWER: Hello Devon,

Yes, I can see from your pictures that your S. purpurea and Venus Flytraps do have good coloration. It also sounds like you use window light and utilize the florescent lights as supplements. That works. It sounds like temperature may be the problem with your Sundews.

Eventually, your Venus Flytraps and Sarracenias will need more light in the long run. S. purpurea needs the most light of all your plants. If you begin to notice elongation and deformity in the leaves of your plants, they will be succumbing to light starvation. In addition, will you be providing artificial dormancy for your temperate plants?

Try to cool off the ambient temperature around your Sundews and see what happens. I do notice when it is too hot or too cold, Sundews tend to produce less dew.

Christopher

---------- FOLLOW-UP ----------

QUESTION: When I got the news lights, the temperature where my plants were located rose from 70.3 to 73 or 74.3 degrees. Could such a small rise in temperature be the problem after all?

My room temperature drops to around 69 at night when the light is off and I have my ceiling fan on to circulate the air.

Answer
Hello Devon,

Then that could not be the problem. The temperature is fine. Does the humidity fluctuate widely? Are there any central air vents or air conditioning units working in that room?

Since the problem began when you added lights, we may have to back to basics. You indicated that the soil dries more quickly with the lights over your plants as well. How much water do you keep in their trays? I notice the trays in the picture of your Sarracenias are dry. Try to keep 1/4 of the bottom of the pots of your Sundews and Venus Flytraps in water and use between 1/4 to 1/2 of pot depth for the Sarracenias. They are bog plants and really prefer that amount of water. I have my Sundews in 4-5 inch pots sitting in about 1 inch of water constantly.

What kind of water are you using? Make sure to use distilled, rain, or reverse osmosis water. Most other sources of the water possess too many mineral solids that can harm carnivorous plants.

Christopher