FlytrapCare Carnivorous Plant Forums

Been running my chest freezer set up for a few months now but I was hoping I could get advice on a few things. For circulation, I have a 3-3.5 inch fan positioned at the top of the freezer that runs 24/7. At first I tried to position the fan so that the main airstream was partially hitting the plants. However it seems that even with 90%+ humidity, some of the plants were drying up fast, particularly the ones potting in airy media like akadama and coco chips.

What is the best way to position the fan in the freezer? Should I have it positioned at the top, but blowing at the back wall so none of the plants are in the direct airstream? Or should I place it below the plants moving air upwards?

My other question pertains to humidity. With the lid I built, it seems like it creates a fairly effective seal. If I don't prop it open slightly during the day, the humidity stays at 95%+ and approaches 100% at night. I have the fan running 24/7 to move air within the freezer, and I try to open it every day for about 20 minutes to get some air exchange. Even with these measures in place, is 95%+ daytime humidity too high even with the fan running? Would it be better if I cracked the lid during the day to keep the humidity in the high 80s-low 90s?

Thanks

I dont have a chest freezer but a grow tent rather. I have my fans about 6 inches above my plants blowing horizontally. I keep my humidity 95%+ and only water once a week or every other week and haven't had any issues.

I’ll be glad to share my year or so experience with a chest freezer. Number one rule, swap out the thermostat for one designed for a refrigerator or wine cooler. Then set it with its adjustment screw so that if the control system you’re using goes haywire, it will never allow the thing to get below 45 or 50F

https://www.flytrapcare.com/phpBB3/pos ... ml#p435015

KingLouis_CLXXII wrote: ↑Thu Jun 22, 2023 9:18 pm I dont have a chest freezer but a grow tent rather. I have my fans about 6 inches above my plants blowing horizontally. I keep my humidity 95%+ and only water once a week or every other week and haven't had any issues.

Thanks for your comment! I guess my main concern with having the humidity at a constant 95%+ was that it would interfere with the plant's ability to undergo transpiration. Because of this, I try to crack the lid to allow the humidity to drop to around 90% as and let some fresh air in as well. But I am curious whether this is really necessary and whether or not a constant levels of near-100% humidity can cause physiological dysfunction relating to impaired transpiration.

Supercazzola wrote: ↑Fri Jun 23, 2023 11:44 pm I’ll be glad to share my year or so experience with a chest freezer. Number one rule, swap out the thermostat for one designed for a refrigerator or wine cooler. Then set it with its adjustment screw so that if the control system you’re using goes haywire, it will never allow the thing to get below 45 or 50F

https://www.flytrapcare.com/phpBB3/pos ... ml#p435015

Accidentally freezing the plants was definitely a concern after hearing similar horror stories! What I ended up doing was buying 2 thermostats and chaining them together so that the first thermostat will kill power to the 2nd thermostat and freezer should the temperature ever reach 50 at night. The freezer is also about 4 feet from my bed in my apartment so hopefully the alarms would also wake me up should that ever happen

Long story…

Just to be clear, even external thermostats can fail. I like your idea. For me, I have smart switches, and use home assistant to control my smart switches. I created a thermostat, fed with 6 different types of smart thermometers. I averaged those and used that temperature as the control for the thermostat within home assistant. I had one smart switch as the master, and chained to that was the second smart switch that was acting as the main power switch to the compressor. I should have made a rule for each temperature sensor, and shut down power to the main master plug if either of the sensors went below 45 for example. Instead i relied on the average. When the Bluetooth / wifi ESP device I used to communicate with a majority of the sensors in the freezer failed, it continued to indicate the temperature was too hot, so it let the power continue. The one or two sensors that were working and reporting correct cold temperatures were lost in the average (for example if 4 sensors said it was 80F and two sensors said no, it was 50F, then the average reported back was 70). If the target was 55, it kept allowing the freezer to do its thing.
Long story short, lost a thousand dollars easily within a 12 hour period. Now I monitor ever temperature sensor and if one goes out of range, or cuts power to the whole thing for an hour and then checks again, etc…

So I was determined not to let that happen again. Now the system has a thermostat made for wine coolers. I had the set screw adjusted to that even if it ran for 48 hours (because I did it with no plants inside), the temperature could not get below 45F, assuming the thing was at it’s coldest. I then rotated the thermostat and let it run another 48 hours and found the sweet spot of 50F.

Regarding the humidity, which I know was your first question, the only plant it seems to have not made happy was my expensive N. Villosa. It got crone rot within two weeks, and I was very careful with that specimen. I have a pair of AC Infinity fans in the freezer. One at the top blowing Left to right, and one under the egg crate, blowing right to left. My humidity does change some over the day / night cycle without me needing to crack open the acrylic lid (from about 88% in day to about 82% at night). My day target temperature is set to 70F, night to 50F.

The humidity requirements, like the temperature, depend largely on the plants that you have growing. Some are more picky than others.

I've generally found most of my highlanders prefer humidity in the 75% ish range during the day, and the 95% ish range at night. Although I haven't noticed much difference if the day humidity goes as low as 65% or as high as 90%, or if the night range goes as low as 85% or as high as 99%. Higher than those ranges I've had some mold and fungus issues, and lower than those ranges doesn't spell "sudden death" but the plants do appear to be considerably less cooperative. But the 75% and 95% targets appear to be a good balance, for me.

But lets focus on three categories: air circulation, air ventilation, and humidity. Temperature also matters, and interplays with the other three, but with a chest freezer it looks like those variables are more "set".
Humidity alone is only one category. If you hit the right humidity levels, but don't have adequate ventilation or circulation, mold develops. The more circulation you add, the less mold issues you have. But the quicker the plants dry out, which requires higher humidity levels, which necessitates more circulation (you get the idea). So it's a balance between the two. You can't really have too much circulation (obviously within reason, no wind tunnels, but slight movement of the leaves appears adequate), but circulation increases humidity need.

Now you enter in ventilation. Ventilation is necessary for a few reasons. For one, fresh air is good for the plants. Beyond that, increased ventilation will decrease your need for as much circulation. But like circulation, the more ventilation you introduce the more your humidity drops. So you need to increase your humidity to account.

The balance between the three depends on everyone's setup. The dimensions, insulation, environment, temperature, humidity levels desired, and plants all dictate the variables.

Most shoot to have daily humidity in the range of 65-75% percent in the day and 85-95% at night. Understanding you need a humidity drop during the day, it's a great opportunity to increase ventilation during this time period, as it will decrease humidity. Most highlanders also need a temperature drop at night, which if you're growing indoors means you need LESS ventilation at night. Much like how a greenhouse will have fans that turn on at a set temperature, but as they're growing outdoors their parameters are in reverse of yours (more ventilation during higher temps to get it down). When you get the balance between ventilation and humidity, you can then increase circulation enough that the system is more or less balanced with all three.

Alternatively, you could get the humidity settings correct, then get your circulation correct before working on ventilation. But that works better in a less sealed growing environment (i.e. NOT a chest freezer that's sealed fairly shut), where you'll naturally lose some humidity throughout the day. Which makes ventilation less crucial, which thus makes circulation much more crucial.

No definitive answers here. But hopefully something here helps.

I know this is late but thank you for all of the advice! Been running my setup for over a year now and things are going ok. I do have one follow-up question regarding circulation. I currently have one 4 inch fan that runs 24/7 and blows a few inches across the tops of the plants. After talking with some other freezer growers, I am considering running the fan on a timer so that it runs for 5 minutes on and then 5 minutes off.

My question is: is there a physiological reason relating to growth processes why alternating my fan to run on/off would be better than running the fan 24/7? Drying the plants out too fast really hasn't really been an issue since the fan doesn't blow directly on the plants. I was just wondering if there might be another reason why alternating periods of air movement might be better than constant (albeit light) air movement. Thanks!

Well, with stronger winds, having shifts in the wind encourages the plant to put down stronger roots and hold itself up. If you've ever seen saplings that are staked to keep them upright, that has to be done carefully, as providing them too much support means they don't have any 'motivation', as it were, to build a proper root system. I don't know whether that applies to a light breeze from a little fan, mind you, but it came to mind.