Quote:
Originally Posted by Pumpkin92
I think I am going to try it. I have a phal and oncidium in mind this might work on (the oncidium has just about finished its new growth that it was working on when I bought it).
I have a few more questions that hopefully someone could help me on:
1) Does there have to be sand/rocks in between the two pots or can I fill it with just water?
2) Will the plant(s) I choose have to be covered with anything to maximize cooling? (I'm asking because I'm not sure if a smaller scale zeer can cool as much as a big one).
3) For this to initiate a spike, I should fill it at night and empty it in morning, right?
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1 If you fill the space with water, it will leak back into your inner pot through the drain hole. You probably don't want to grow it as an aquatic plant, though some people do grow some orchids in water. You could grow the orchid in an inner pot with no holes, but that isn't a good idea most of the time. Sand, not rocks, is what you want between the pots, because sand doesn't move when settled, and it wicks water better than larger particles.
2 The cooling comes from water evaporating from the outer clay pot. The roots are cooled. Cooling will be proportional to the surface area of the outer pot. The larger the outer pot the greater the cooling effect. Evaporative cooling only works when the dew point is below 55 degrees F / 13C. If you look at your local weather on weather.gov you can find the current dew point. In El Centro your humidity is almost always very low, so the dew point will almost always be below 55 degrees F.
Most orchids don't do well enclosed under a bag or jar when their roots are wet, so don't do that.
3 If you are going to use this method to cool your plants, the sand between the pots should be moist all the time. You need to use very pure water for this technique or salts from the water will quickly build up outside the outer pot and inside the inner pot, and potentially burn roots.
If you use 2 nested clay pots with sand in between, the moisture in the sand will also wick back into your orchid root ball. Water conducts heat quite well, so this would lead to the best cooling. If I used this technique I would be sure my plants were in a very well-aerated mix, such as very large bark. Fine mixes might stay too wet with too little air.
If your orchid is in a plastic pot nested in a clay pot, the cooling will still take place on the surface, but less water will wick from the sand into your orchid, since it will only go through the drain holes. Plastic does conduct heat but not nearly so well as wet fired clay.
Or you could grow semi-hydroponic with a single clay pot standing in a dish of water and LECA as growing medium, and get a similar effect. The water would wick up the clay pot and evaporate, cooling it. There is a large semi-hydroponic forum here on the Orchid Board. Most people who use this method (including me) use plastic containers because that is how the method was first described, and we aren't aiming at cooling. But after reading this thread, I think I'm going to try clay pot S/H for something that needs cooler temperatures and see how that goes.
Hybrid Mode
