Lotsa blue
Sep 5, 2011
Vancouver, Washington State, US
Thanks for the offer, Collin! That is very generous of you. Fortunately I am feeling more confidant that my little plant is actually humboldtii. So far, it is neither visibly growing nor is it failing, its one little terrestrial leaf sticking up. Our temps are still kind of cool but it will warm up as the seasons progress.

Very interesting information. A suggestion - do you have access to a microscope? It should be possible to observe the guard cells and stomata on the leaves of utricularia at different times of the day to see when they are open and when closed. 'Just a thought.
Apr 13, 2015
Los Angeles, CA
That's a great idea. And thank you for suggesting that; I really appreciate it. I do have access to one. And, these plants are CAM plants.
So, what does this mean for the cultivation of these plants? Well, in order for a plant to be happy it needs to have access to CO2 and to get rid of O2. These plants do most of that gas exchange at night. And, it turns out that stomatal conductance (how much gas can pass through the stomata) depends on a few factors that we can control. Here's a paper about that, if you're interested in doing some further digging. Based on this paper, here are the external factors that control stomatal conductance.
  • Humidity. This one is the one tidbit that's new; the important finding. Because these plants are epiphytic, their stomatal conductance is especially sensitive to relative humidity. Because of this, I try to modulate the humidity in the terrarium over the course of the day. At night I'm regularly fogging with chilled water (which helps drop the temp as well) and keep the humidity at 90-95%. During the day a fan vents out air to drop the humidity down to 45-55%.
  • Light - maybe, we aren't sure. But, I keep these plants under brighter light for a shorter photoperiod (which also happens to be the photoperiod that they receive in nature). I'm guessing that a long photoperiod for these plants will not be terribly beneficial as they will run out of CO2 and build up O2 over the course of the day.
  • Temperature. Low nighttime temps lead to better conductance, usually between 15-25C. So, I grow these plants with a daytime high of 27C and a night time temp of 17C (at least on one side of my terrarium, I'm still working on keeping the temperature more consistent across the length of my terrarium). This is already aligned with how most people grow these plants.
  • Leaf water potential. Without any water, the guard cells don't open. Read: plants need water. Nothing new here. I keep these plants in media which drains well but is always moist, a mix of live long fibered sphagnum and pumice.