Translucent containers and heat buildup

[xscd]

One of the concerns I have about semi-hydro cultural techniques regards the (optional) use of translucent containers, and the heat buildup that occurs in any space where sunlight enters and then is trapped to some extent.

Part of the reason for this concern is that I live at a relatively high altitude (above 4,000 feet) here in eastern New Mexico, US, and the sun here, shining through less of an atmospheric buffer, coupled with frequently cloudless skies, means that even traditional planters made of clay or opaque plastic, when placed in full sun, can literally bake and kill roots and often the entire plant. I'm not kidding. It has happened quite a few times in my experience.

That's what makes me concerned about using translucent containers with orchids. Even in my greenhouse (just a walled in, multiwall-polycarbonate roofed converted backyard concrete patio) the sunlight in the summer can be pretty intense and the heat buildup in that growing room can be surprisingly rapid.

I'm wondering about the effects of sunlight entering the sides of the tranlucent semi-hydro pots and, like the sunlight entering my grow-room, causing a rapid and intense buildup of heat just inside the container where a lot of roots may be exposed to that light and heat. I'm thinking that the PrimeAgra (or any leca with its highly insulating properties) might make the problem more acute.

For my sun-loving carnivorous plants, I have converted to the use of the new urethane foam planters to prevent the planting medium from overheating. It works well. The planters are opaque (and I usually choose light colors) and they provide a highly insulating layer, like a styrofoam beverage cup does for hot coffee.


In fact, I just punch a hole in the bottom of cheap white styrofoam 16-ounce beverage cups and use them for a lot of my carnivorous plant seedlings. I could use these styrofoam cups, and the larger urethane foam planters, for semi-hydro planting as well, but would then not be able to observe the water level inside the built in reservoir. However, I suppose I could just drill a hole in the bottom of such containers and set them in an external reservoir and observe the liquid level that way.

Any comments or additional thoughts and ideas about this subject, anyone?

[xscd]

Despite my apprehensions about heat-buildup just inside the walls of translucent planting containers, yesterday I planted several orchids into translucent semi-hydro pots and will see how things go.


I'm not too worried about the paphiopedilums because they will be relatively shaded. The phalaenopsis will be exposed to more light, but I'll just wait and observe whether heat-buildup becomes a potential problem or not. My few cattleya-alliance orchids are typically exposed to the most light of my orchids, but I haven't potted any of them into semi-hydro yet. I may try one or two in translucent plastic semi-hydro containers, and I may repot others into opaque plastic or urethane foam or clay pots, using PrimeAgra leca and an external reservoir, to see if there is any difference during this next year, 2007.

Best wishes all--

Steve / xscd

[Ray]

Steve,

For one, the solar heat gain will be substantially offset by the cooling provided by evaporation of the water. I have grown plants in full sun in clear pots with no issues.

Secondly, unless you're diligent about periodic treatment with Physan or a bleach solution, your pots will become a haven for algae on the walls, and the penetration by the sun's rays will be significantly diminished.

[IdahoOrchid]

I also believe that darker containers will absorb more heat than a lighter one would, even if it is clear.

A neat experiment would be to place a thermometer in a pot with each type to see which conducts more heat to the inside of the pot. I will not be able to do that until I get some s/h materials.