placing plants on a heat mat

[neophyte]

I recently got a heat mat and was wondering how to place plants on it. Can I place pots directly on the mat, or does there need to be some sort of separation (especially for plastic pots)? Also, for clay pots, since clay isn't a great conductor (and often there's a clay tray to collect water underneath the pot), how useful is the heat mat, anyway?

[3rdMaestro]

I'm assuming you are referring to a heat mat like would be used to germinate seeds. I've used them for general gardening, like starting pepper and tomato seeds. I can tell you that they don't get hot enough to damage plastic pots. Clay pots will get warm if you place them on the mat, it just takes longer, and if they are wet, it will warm the water and evaporate it a tad faster too. But it should warm the clay still. As to the effects on orchids specifically, I feel like I've heard of people using them to accommodate warm and hot growing orchids indoors but I've never personally done it. Hopefully someone else will be along to comment on that momentarily....

[Orchidtinkerer]

How useful they are really depends. Ideally you want to use them as little as possible as they can dry an orchid out in no time so need more watering. I try to avoid placing pots directly on the heat mats. I have a bit of unique pot design that has a 10cm base/gap between the bottom and the substrate. Otherwise I use polystyrene insulation under regular pots but I wouldn't advise placing it under every pot as that will just block all the heat going up. A plant stand or tray would be best which is what I have in places to create a second level. A humidity tray can be a good idea to raise the orchids a bit and add lost humidity.
I had two orchids that suffered from cold this year. So my choice was to turn up the central heating or use a heat mat. The leaves were going yellow in places from the cold and since using a heat mat (during the day only) that has stopped. My house is very badly insulated and I could turn up the central heating but I would rather use heat mats.

So it depends on your preferences and situation. I have display cabinet for my main orchids which uses 90watts to heat to 24 degrees.

In comparrison I build an insulated box above my reptile enclosure that houses my hot growing orchids (29 C) and that only requires 1 watt of heating. It gets most its heat from the reptile enclosure and led lamp which is great, I have 5cm insulation boards that keeps the heat in.

So try to minimise heat loss, use heat mats to create a temperature difference between night and day which will benefit all orchids and make them stronger even if they still have to endure the same harsh cold nights they will be able to do so better.

Most houses do not replicate this day to night temperature difference which is one of the biggest advantages of a greenhouse, most houses are fairly steady in temps so the main benefit to using heat mats imo is to be able to create that temperature difference.

Some orchids don't need too big of a difference, others benefit more , most of that information can be found online if you research it.

edit: what 3rdmaestr says is very true btw, I am referring to reptile heat mats, to me the plant heat mats are only good for seedling trays, ie anything under 5cm tall.

one more thing I should mention is that it should ideally be an adjustable heat mat or you should have a thermostat controller to control it and always check how hot it gets around the orchids. Don't just plug it in and leave it, heat mats can be a fire risk if not used correctly.

[Ray]

As has be mentioned, there are heating mats and there are heating mats.

If yours is a "windowsill" mat (3"x20", 7W) or nursery tray size (10"x20", 13 W), there is no need for a thermostat. Others may need them.

[realoldbeachbum]

Originally Posted by neophyte

I recently got a heat mat and was wondering how to place plants on it. Can I place pots directly on the mat, or does there need to be some sort of separation (especially for plastic pots)? Also, for clay pots, since clay isn't a great conductor (and often there's a clay tray to collect water underneath the pot), how useful is the heat mat, anyway?

I found this inexpensive heat mat on Amazon that works great for seedlings or repots with no roots. It also works great for placing under plants near windows on cold nights. (I actually have placed it standing on edge between cold window and plant.)

Plastic is OK on it because it doesn't get hot -- just slightly warm. There is no way to regulate the heat, however.

I have found them so useful that I now have 4!