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Discuss water requirements, "soil" (growing media) and suitable planting containers

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By Gary
Posts:  410
Joined:  Fri Jul 08, 2022 3:23 pm
#436654
Hi all,
Each of my plant containers is black, and I'm wondering if this may pose a problem for root temps. The summer sun in AZ heats the media and I'm concerned about overheating. I know that Darlintonia need to have cool roots, but I don't know about VFTs and other Sarrs.
Has anyone tried pot temperature mitigation, such as wrapping them in foil or setting the pots on white cloth (the tables I set the trays on are dark brown and can get pretty warm). Or perhaps I'm just being overly concerned?
By davinstewart
Location: 
Posts:  338
Joined:  Sat Jul 13, 2013 2:29 pm
#436655
I've experimented with this some and the color of the container does make a difference, although it's not as much as you think.

I have a watering table which automatically waters my plants every day at 2pm and under those conditions the biggest factor was preventing sunlight and moving air from reaching the soil mass. What I found was that using something like white growbags which could be smooshed right up against each other not only saved space but was the most effective at reducing the soil temperature. I'll see if I can get some pics and temp readings to share.
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By wcrosman
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Posts:  408
Joined:  Thu Apr 14, 2022 2:03 am
#436666
I double pot mine. Inner pot light colored. Outer pot white. Space of about 1/2” between the pot. It acts as insulation keeping direct sunlight off the grow pot.
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By MikeB
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Posts:  1837
Joined:  Sat Apr 25, 2020 4:13 pm
#436680
I read a post from a grower in Spain who definitely had heat problems. He could only find black pots, and they got hot in the blazing sun. His solution was to wrap the pots in aluminum foil.

wcrosman's idea of a pot-in-a-pot works well, too (if the outer pot has no drain holes, then it becomes the inner pot's super-deep saucer).
By Gary
Posts:  410
Joined:  Fri Jul 08, 2022 3:23 pm
#436681
Hmmm. I'm using cut-down translucent water jugs as trays but they're sitting on dark surfaces that get quite hot. During this time of year the sun is nearly overhead so perhaps the pot color isn't a big factor. I'll check water temps in the trays as-is and then try setting the trays on a white towel and see if there's a significant difference. I don't have a way to build a heatsink under the trays (yet).
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By Intheswamp
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Posts:  3125
Joined:  Wed May 04, 2022 2:28 pm
#436688
If the pots/trays are sitting on cement or other dense material that acts as a heatsink then they're basically sitting on a hotplate. :shock: Rather than a white towel, what about getting a piece of 3/4" rigid foam insulation and cutting pieces to set the pots on? I would not cut individual pieces for each pot, though that would help with heat conduction coming from below. I would cut larger pieces of the foam that multiple pots could sit on...this would help with conduction heat but also with convection heat rising around the pots. Anything to stop the heat from conducting from one material to another and to reduce the heatwaves rising from the dark surface will help. A solid foam piece will still let the heat rise around the edges so a bit of a buffer zone (extra foam) around the edges would help divert the rising heat further away from the plants. It's not exactly something you would see on the cover of "Better Homes & Gardens" but if you need it more aesthetically pleasing then you might could wrap it with a light colored fabric of your choice. FWIW. ;)
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By Gary
Posts:  410
Joined:  Fri Jul 08, 2022 3:23 pm
#436691
I'm liking this idea. The larger water trays are sitting on dark brown Trex deck boards and the smaller plants are on a dark brown plastic bin. I have some white Styrofoam shipping container lids that will work to insulate the trays. Thanks!
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By Intheswamp
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Posts:  3125
Joined:  Wed May 04, 2022 2:28 pm
#436698
Double pots aren't a bad idea, either, but my be problematic in your water trays....possibly cut the entire bottom out of the outer pot and use it as a sleeve to shade the inner pot. One thing I have done on a double pot is to shove thin foam down between the pots for some added insulation. I used some old styrofoam cups I left over from some vegetble seedlings...flattened them out and shoved them down into the gap between the pots.

I think at your location that lack of rain is more of an issue than getting too much rain. Some surface plants in the tray would help conserve and cool the water....utrics or some of the more surface-covering non-carnivorous water plants.
By Gary
Posts:  410
Joined:  Fri Jul 08, 2022 3:23 pm
#436707
It sure sounds like an insulating layer would fix this issue. The water in the trays gets pretty warm, and I've been concerned about it since last year. The monsoons will be coming in about 2 weeks and will fix the low humidity problem, but I have to protect the plants from the heavy rain, hail, and high winds.
By Barlapipas 6
Location: 
Posts:  476
Joined:  Tue Aug 30, 2022 11:26 pm
#436717
Here in Greece it got pretty hot last summer. It reached 38°C every day for 2 months straight. My plants were on the sun from morning till 3:30 pm. I was watering them from top every day and they thrived. Even my VFTs that were in a small thin light grey plastic pot. But I have felt A LOT more heat on the brown trays of my Sarracenias than the white tray of my VFTs. Now most of my plants are in white pots with white trays to minimise heat and it seems to work. Now if the pots or trays are black the heat will get you into trouble probably. If you want more protection from the heat then do what the others suggested.
By Gary
Posts:  410
Joined:  Fri Jul 08, 2022 3:23 pm
#436719
I checked the tray water and media temps, both are in the mid-90s. The plants don't seem to mind, but the hottest weather is still to come here. I'll see if preventing heat from radiating up from the dark brown table and deck planks makes a difference.
I know that plants in the wild don't get this sort of TLC and they survive just fine, but there's a reason that CPs aren't native to AZ and the heat is a big factor.
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By MikeB
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Posts:  1837
Joined:  Sat Apr 25, 2020 4:13 pm
#436721
Intheswamp wrote: Tue Jun 20, 2023 4:42 pm One thing I have done on a double pot is to shove thin foam down between the pots for some added insulation.
I've also seen people fill the gap with perlite.
Barlapipas 6 wrote: Tue Jun 20, 2023 9:05 pm A LOT more heat on the brown trays of my Sarracenias than the white tray of my VFTs.
A few years ago, I checked my trays using an infrared thermometer. One black tray, one white tray, about 1 inch / 25mm of water in each, middle of July, 3 PM on a sunny day. Both trays were warm, but the black tray was much hotter. When I stuck my finger in the water, I could tell that the black tray was acting like a solar water heater. After that, I moved all of my plants to white trays, even though they're 2-3 times as expensive as the black ones. I still use some black watering bowls with my Sarracenia, but those bowls are shaded by tall grass or by the pot in front of them.
Gary wrote: Tue Jun 20, 2023 10:05 pm I know that plants in the wild don't get this sort of TLC and they survive just fine, but there's a reason that CPs aren't native to AZ and the heat is a big factor.
Wild flytraps grow in soil that contains a lot of white sand, and that reflects a good portion of the sun's heat. The leaves may get a bit warm, but the rhizome and roots are cooler.

For desert / hot-climate growers, this is a good video to watch:
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By andynorth
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Posts:  1209
Joined:  Fri May 12, 2023 9:08 pm
#437107
I just yesterday added more Silica sand to the tops of all my plants. VFT's, Pitcher's, Sundew's and Sarracenia's. Below that is a layer of NZ Sphagnum Moss. This seems to work both to keep moss from accumulating and as a sun reflector from the soil but not the plant. I will post my results if they are good. If bad, then I will mope.
By Gary
Posts:  410
Joined:  Fri Jul 08, 2022 3:23 pm
#437204
I found some thin foam white table placemats and put them under the Sarr water trays. The water temps dropped ~20 °F. I did have to bring the Purp hybrids inside, setting them in shady light helped but those pitchers are very thin and <10% humidity was drying them out. The rest of the week is going to be way hot, so they're under the lights for a few days.
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