Heating mats

[Piper23]

I set up 2 Vevor mats (pic included). I set the target for 80 degrees. Neither rises above 63 degrees (5 hours in). I have tried with and without a layer of bubble wrap beneath the mats (they seemed to be heating the metal cabinet they are sitting on without the bubble wrap present). The room temperature is 68 degrees.

Advice?

[sunfire]

I use a piece if styrofoam insulation board under mine.

[Dimples]

I use heavy duty cardboard under mine. It’s easy to come by for free and it’s a stable surface.

---------- Post added at 03:33 PM ---------- Previous post was at 03:28 PM ----------

Also, dry medium doesn’t hold or transfer heat well, and the chunkier the mix is, the less heat it will transfer.

Your phals look dehydrated. Are they recovering from root issues? Putting a clear storage bin over the top of the grouping will boost local humidity and help keep them warmer too.

[estación seca]

If you set a thermometer directly on the mat it might be 80 F. In an open room that cool the hot air rapidly rises off the mat and is replaced by cold air. Objects above the mat will be heated somewhat. Objects on the mat will be heated a little more, including pots and media.

I suggest putting down an excellent insulation layer, like styrofoam/polycarbonate foam. Then the mat. Then a metal tray even slightly larger than the mat, filled with dry sand. That will warm the pots more.

I have used the above method with a large heat mat, an oil drip pan filled with sand, and an enclosure around the setup made from foil-backed polycarbonate foam building insulation sheets.

[Piper23]

I struggle with determining when to water.

I get the sense from reading from this forum that air circulation is key which is why I chose the media used here. Would one of you suggest a better medium for better hydration?

[minicoerulea]

Though I defer to the much more experienced folks here, I think that a different medium would not help a person know when to water -- that knowledge comes from experience, and especially from experience with a certain medium.

Repotting again probably wouldn't be a good idea. I'd recommend picking a reasonable medium (like the one they're in now) and figuring out how to grow in it. That can take a lot of time (it does for me, anyway).

Another comment: if your room temp is 68, the mats can't be 63. There's some measurement error going on here.

[Ray]

The primary “trick” to growing orchids is finding a way to provide plenty of water and plenty of air at the same time.

With that coarse mix, you should try to keep it moist at all times, as the air part is apparently no issue. There is no need to let it dry out; that is only necessary when too dense of a potting medium is used, allowing it to become soppy and suffocating when it is watered.

Your problem now might be getting that stuff to hold water, but that can be easily overcome:

1) using tepid water, flood the living daylights out of the potting medium. If you’re doing that under the spigot, turn up the volume to medium volume and water everything until it’s wet and the water is flowing through.

2) wait 15-30 minutes and repeat.

After that, don’t let it dry completely before rewatering and it’ll hold more water with a single wetting.

[Dalachin]

Heat mats get warm to the touch but they don’t heat up the ambient air very much unless there is something to trap the heat. Mine are set at 77-78 but the ambient air varies from 65-75 in the winter, depending on other factors.

All my plants on mats either have outer liner pots or are in plastic bins, or both. Or they are semi-hydro, but that is another story. I use containers from the recycling as outer pots, some I cut down, others fit the top rim of the inner pot and there is air space underneath. I use these outer pots to help soak the bark when I water— I’ll fill the pot, let it sit a few min or as long as 20 min, then dump the excess water from the liner pot. When not watering, the liner pot helps keep the humidity near the roots. For the liners that fit perfectly at the rim with air space at the bottom, I often leave water in the liner pot. In the winter with the heat pads on, liner pots really seem to help keep even humidity in the pots.

[msrebekahjane]

Originally Posted by estación seca

I suggest putting down an excellent insulation layer, like styrofoam/polycarbonate foam. Then the mat. Then a metal tray even slightly larger than the mat, filled with dry sand. That will warm the pots more.

I like the idea of the filled tray. How about filling it with lava rock or Stalite and add water to the tray, and pots next. Should get good heat transfer as well as added humidity.

Thoughts

[Dimples]

The heat mats won’t have the power to raise the temperature of water enough. Sand doesn’t absorb heat at the atomic level to move from one phase to another, like water does, heat just passes through the sand particles as it rises and spreads out a little.