My cobra lily setup with recirculating water

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mcgrumpers

 
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My cobra lily setup with recirculating water

by mcgrumpers » Wed Aug 14, 2019 6:58 am

I've had a cobra lily for about two weeks so I am in no way recommending this setup. I am simply sharing what I've found so far.

I read about several cobra lily setups in which a pump recirculated water into the container and/or tray, attempting to keep temperatures down and to mimic the natural conditions in which they grow. It sounded cool so I made one of these setups as follows:

cobralily_setup.png
cobralily_setup.png (10.16 KiB) Viewed 146 times

Materials:
  1. A small white garbage can from walmart
  2. A piece of styrofoam cut to the size of the garbage can and with a pot sized hole in the middle (see orange)
  3. A 6" container with a cobra lily planted in LFS with a handful of pumice (see green)
  4. A solar powered pump (see gray)
  5. 1/4" tubing taking water from the pump to the cobra lily pot (see purple)

The solar powered pump is a cheap fountain pump from ebay (something similar to this)

The garbage can holds distilled water that, when there is sun, the pump moves into the cobra lily pot. The theory is that the white container is able to reflect light and reduce the rate at which the water heats up, and that the recirculating water can keep the cobra lily roots cool (because cobra lily roots are allegedly sensitive to high temperatures).

Alas, it seems this theory does not hold in practice.

Take a look at this plot showing the air temperature (red) and the soil temperature (green) throughout the day.
aug7.PNG
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At first, as the temperature rises in the morning, the soil temperature is lower than the air temperature. It makes sense that it takes longer to heat up the container, the LFS, and the extra water in the container. However, the soil temperature ends up catching up with the air temperature, and by this point, the recirculating water is quite warm. Furthermore, once the air temperature goes down, the soil temperature takes longer to cool down as now that LFS/water is holding extra heat that also needs to be cooled down.

In the end, both the air temperature and the soil temperature were above 30 C for about the same amount of time (~1h 40m).

So my setup doesn't seem to reduce the time during which the cobra lily roots are hot. Not cool. Maybe it could make a difference if your water container is really large (and thus able to stay cool for way longer), but I have no data on that.

I tried placing a frozen water bottle into the water, and that effectively brings down the temperature, but it's too much effort to do on a regular basis.:
today.PNG
today.PNG (24.54 KiB) Viewed 146 times


With what I've learned so far, I'm leaning towards leaving the setup as is even though it doesn't keep the cobra lily cool... at least I don't have to worry about watering it and perhaps the moving water is good for the plant. I'm going to hope that it can take the occasional heat as temps aren't this high for long.

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Jeeper

 
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Re: My cobra lily setup with recirculating water

by Jeeper » Wed Aug 14, 2019 5:21 pm

Thought, bury the garbage can? Let the earth be a heatsink to somewhat regulate the water temp?

Another thought, somehow add a temp sensor so that the pump only runs when there's sun and only when it reaches a certain temp?

I just aquired some DC seeds so I'm working on my own design, but yours is a good start!
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Re: My cobra lily setup with recirculating water

by steve booth » Wed Aug 14, 2019 9:57 pm

The water will warm to ambient and so won’t cool the pot as it can’t get lower than the air temperature. The set up could work if the pot was porous and the small white rubbish bin was filled with a wicking agent such as Sphagnum and water, the evaporation drawing heat from the porous pot and keeping it below ambient temperature (humidity conditions allowing)
Cheers
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Re: My cobra lily setup with recirculating water

by mcgrumpers » Sat Aug 17, 2019 6:12 am

Jeeper: burying is an interesting thought, though I can't test it out as my cobra is on a balcony. The solar pump only works when the sun is out so it does a good job of only running when needed. I don't want to minimize the number of non-trivial parts in my setup so more complex type of feedback are out of scope for now.

steve booth: sounds like you're suggesting a zeer pot! If I understand zeer pots correctly, only the outer pot has to be porous, so it would be fine to use a plastic pot for the plant itself. A slight variation would be to cover the inside of the white garbage bin in dura cool fabric and to attach a solar powered fan to move air from inside of the bin to the outside air. Turning on the fan would in theory cool down the bin (through evaporative cooling). No idea if the effect would be significant but perhaps worth a try.

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Re: My cobra lily setup with recirculating water

by SundewWolf » Mon Aug 19, 2019 4:26 am

It's nice that you have actual data instead of just doing things blindly. You could always drop a couple hundred for an aquarium chiller and hook that up to the water basin. Or similarly do it ghetto style DIY with a mini-fridge, some tubing, and a pump. Not sure how necessary it is though, depends on where you live. In cooler states I have seen people get away without even having the pumps. I still run my solar pump and my cobra is growing and dividing, although it does slow a bit in the middle of summer and potentially throws out a deformed pitcher. I still want to run it for about 3-4 years to see how grows and then decide if I personally want to get a chiller or not. Honestly I probably will when I build a greenhouse and just make a whole chilled swamp of Darlingtonia in the corner.
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Re: My cobra lily setup with recirculating water

by steve booth » Mon Aug 19, 2019 2:57 pm

mcgrumpers wrote:steve booth: sounds like you're suggesting a zeer pot! If I understand zeer pots correctly, only the outer pot has to be porous, so it would be fine to use a plastic pot for the plant itself. A slight variation would be to cover the inside of the white garbage bin in dura cool fabric and to attach a solar powered fan to move air from inside of the bin to the outside air. Turning on the fan would in theory cool down the bin (through evaporative cooling). No idea if the effect would be significant but perhaps worth a try.

Yep indeedy, that was exactly it, the fan and fabric would work the effect being entirely dependant on the U value of the plastic and moisture content of the air, (plus any direct evaporative effect due to the airflow over the surface of the soil) but as you suggest worth a try and I for one would be interested to know how it works out.
Good luck
Cheers
Steve


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