Heat mat use and temp control, with S/H

[Dalton]

Hey all,

I've been reading through the S/H section again, getting some great advice. Something I plan to setup today is a heat mat. I have Sandlewood heatmat. I believe it's 10"x20" or something close to that. I have recently transferred (2) orchids to S/H as well as having a couple of new orchids that are still getting established and used to my growing environment.

To help them out, I want to use my heat mat, but I've never used it before. I do have a cheap seed starting tray and the heat mat is supposed to be 100% water proof. I'd bought a thermostat to control the temp on the heat mat. However, I don't quite know how I'd use it. With soil in the seed starting tray, you'd just stick the thermostat probe in the dirt and it would turn it on and off based on that temp reading.

How would you do that with S/H, or should you. If I can use the controller, do I just stick it in the top of the S/H pot or should I stick it in one of the drain holes, for a reading lower in the media. I also want to put a Podangis Dactyleras (probably butchered that name) on the heat mat as well. I plan to put a small container of water in amongst them as well. I figure it that at worst, it can't hurt anything and at best, the warm water will raise the humidity some in my room. I think ambient humidity away from the mass of plants is around 50% and it bounces up and down a little.

If I were to stick the probe in the top of the media, I worry that the small orchids in the tiny pots would over heat.

[Salixx]

I'm not sure if this helps at all, but I have a similar seed starter mats for my newly transplanted s/h orchids and my warm growers and my orchid seedlings.

This is what I have: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Mine is designed to simply be 10-15 warmer than ambient temperatures. I don't have any means of controlling it other than to unplug it. I, personally, just leave it plugged in except on the hottest of days (85+). Those nights, depending on the temp drop, I might plug it back in. At worst, the heat mat is warm to the touch - it's never hot.

As for the plants, when I water, I tip the pot a bit so that it drains slightly below the drain holes (keep in mind also, that water might expand and leak out as it warms). I place the pots directly on the heat mat and wipe up the occasional spill or leak.

As for your humidity idea, I think it's fine. You might even improve it a bit by adding some leca to the bottom and just putting enough water in to the top of the leca. The leca will increase surface area and thus in theory increase the evaporation rate. The water surface will also be closer to the heat mat, which will help evaporation. I am currently using this technique on two under the weather orchids. One, an oncidium seedling with no roots (been in a holding pattern for over a month) and a Schoenorchis fragrans. The only difference is that I put a top on the container to trap the humidity in and there is always a thick layer of condensation on the walls of the container (the plants are suspending, not in water)

[Ray]

The use of such small-wattage heat mats under S/H pots is somewhat "self-controlling", as evaporation from the pot will cool the medium.

[Dalton]

Salixx, I'm pretty much right there with you. My mat is almost identical, it's just anther brand. I wasn't sure how warm they actually got. I figured that if people were buy thermostats to control them for seedlings, then they might be getting to warm. If they self regulate to 10-15 degrees warmer than ambient, then that'll probably be fine. I can just leave it plugged in.

I don't have mine outside, they're in my bedroom, but that's funny when you talk about the hottest of days (85+). I'm in SC and It's consistently 96-100deg+ all summer, with a high RH most of the time. It was raining most of last week and stayed fairly overcast and I don't think it every got below 85Deg but a few times.

Ray, that's good news. I want to warm them like your site suggests, I just didn't want to cook them. What do you think about the plants in bark in 2" pots? Do you think they'd over heat just sitting directly on the mat with no temp control or should I add a wash cloth under them to make the heat a little more indirect?

Thanks for the help, guys.

[daddydoall]

I use base heat regularly with SH and non-SH in the winter. Some of my bench tops are concrete with embedded heating coils. I use a thermostat set at 55-60 F mounted a foot above the bench, but on cold nights the air temp will still be as low as 40 so the heat will stay on all night. The roots love the heat but evaporation from the media is much faster (naturally increasing local humidity to the leaves, but drying the roots if not careful) and thus you will need to water more often. I try to avoid wetting the foliage in the winter.

[Ray]

As was stated before, they will boost the root zone temp by 10°-15°F, so if you know the ambient temp, you should be able to decide for yourself.

From a practical perspective, the only "negative" I have ever seen from their use is the need to water more frequently.

[Terrariumsandtea]

I use a small potted house plant and stick the temp control gauge in that, above the mat, and then put all my orchids around it on the heatmat since some are in terrariums.