Warm-growing orchids, such as Vandas, Cattleyas, most Dendrobiums, and summer-blooming Phal, require constant growth during the year. To promote this growth, it is essential to place objects above the mat and on the mat, including pots and media. A heat mat or “hot bath” (aquarium heated water bath) can be used under all seedlings, especially deflasks and compots, in a hydroponic tent.
In general, temperatures between 50° and 80° F (10° to 27°) are ideal for orchids, but occasional brief periods of temperatures above 100 F (38 C) or drops into the 30s (0 C) will not harm most orchids as long as no additional warmth is provided. Place your plant near a heated vent, fireplace, radiator, or other heat sources, or consider placing a small space heater next to it for additional warmth.
Heat the root zone directly by placing an inexpensive, horticultural heat mat under the pots, keeping the pot, reservoir, and medium warmer than the surrounding environment. Leave the overhanging sides long and place the heat mat on top of a slab of polystyrene foam building insulation. Heat mats accelerate evaporation from the medium, so increase the watering frequency to prevent drying. Clay pots will get warm if placed on the mat, but it takes longer.
A timer plug connected to an app on your phone can be set to turn on and off at sunrise and sunset to simulate day. A small heating pad under a humidity tray might work for plants that require extra moisture, but it would have to be adjusted accordingly.
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Hi Amanda, I’ve just found your website and am going to work my way through your articles as I enjoyed the first one 😊. I have about 150 orchids which includes 25 Cattleyas and the same number of Den Phals, so am wondering what you would suggest to keep this number warm at night in winter. The central heating goes off when we are asleep so the only thing I can think of is an electric radiator which works out quite expensive.
I’m not sure what country you are in but most plant folks don’t call it a heating pad and you don’t want to use a human heating pad. You could do serious harm to your orchid roots not to mention drying them out even more than your dry winter house heat does. There is also a fire hazard to run them constantly and they aren’t meant to be used around water or high humidity. Whatever you use — make sure the surface it sits on is waterproof and heatproof. If you need to use something to boost heat levels – what you want is a propagating mat that is used under seedling trays. Any greenhouse supply house can supply one. Do an internet search on “commercial propagating mats” and you will find a number of companies. They come in various sizes and options. Read carefully, go to the manufacturers website for the one you are interested in (not just the seller) and also do some reading on the proper use of them for your purpose. You want one with a controller and sensor that goes in a separate pot of potting media or one of the plant or in the tray of soil when doing seeds. It won’t read if dry. These you can set at the temperature you want. Be forewarned, unless you are paying top dollar, these can be very inaccurate. I have tested a few and 15-20 degrees up or down or not working at all isn’t uncommon. They are best used with potting soil — they have a hard time with orchid bark, lava rock, etc. I haven’t tried with sphagnum moss but whatever you put the sensor in, it should match your orchid’s.
We keep it pretty cool in the house, 62-75 degrees F depending on the season but the countertops where I keep most of my plants are usually pretty cold. I got a heat mat for some seed starting and I just put my pothos on it because it was in the same spot anyway and they exploded with new growth! I mean I got new leaves from the center and a whole new vine on each! The heating mat actually isn’t hot to the touch but when I pick the plants up and feel the plastic container it just feels warm. I do have to water a bit more but that actually suites me well because I tend to over water lol. I also put my propagations in water in a glass and on the heating mat and it does wonders!
Absolute silliness. If you put a heat mat under a plant you will cook your plant. (Many people have also cooked their reptiles) You must always use a thermostat, that controls the temperature of the heat-mat. These mats will get up to 50C, if not regulated by a thermostat. This is obviously too hot for plant roots. If you want your tropical plants (or any plant for that matter) to grow through cool weather you must supplement warmth and light. Adding heat under the plant will not cause root rot, it will do the opposite. Added heat and light will allow the plant to grow, so the plant is able to up-take water and use the extra light for photosynthesis. Supplemental heating will cause your potting media to stay healthy, allowing biological activities, nutrient cycling and increase media biodiversity. Long ‘leggy’ plant growth is caused by insufficient lighting. The plant can offen turn pale and not develop properly as it races to get to a light source it can detect. So if you’re giving you plants extra lighting, (usually LED) make sure it is at the correct distance and the plant will grow normally. So, please ignore all the information in this article. If you want spectacular growth of a tropical plant indoors over winter (without having a heated conservatory) you’ll need a heat mat and thermostat and LED light. Set the thermostat to 24C, when the heat mat gets to 25C, the thermostat cuts power to the mat and stops it cooking roots and killing the plant. As the mat cools the thermostat allows the mat to heat again.
I’m using a heat mat under one of my propagation boxes which is dedicated to propagation and seedlings and the results have been great so far. Bear in mind that I do use a thermostat set to 20°C, so it’ll usually only turn on at night because the lights generate enough heat to keep it at 22-23°C during the day. Once my cuttings have pretty well established root systems, I will either move them to another prop box with half the light level to encourage more leaves growing or I’ll acclimate them to the room’s humidity level (~50%) if they already have three leaves or more.
Hi Memo Thank you for sharing your experience with heat mats. As usual it’s the best advice I found I grow mostly orchids in a sunroom that often gets a bit below 19 degrees C in the winter and decided to get a heat mat for my new transplants and was shocked to find how hot the pots got and decided to stop using it until I learned more. I was also asked by my daughter to create a jungle in her New York apartment. Your articles have been really instructional in helping me chose plants I knew very little about Thank you!
I am a first time propagator and looking for solid tips as the internet is not quite clear on the conditions and tools needed to propagate my snake plant cuttings. Currently I have them on a heating pad with the humidity domes and grow lamp. It’s only been 2 days and after perusal your article (great great info btw 😊). I think I should take the humidity domes off. I also added a wire rack between the heating pad and pots. I watered them today as it seemed really dry. Any tips would be greatly appreciated!!
Very helpful, thanks Memo! It’s coming into autumn here (Australia) and my mind had turned to heat mats so this is some useful feedback 🙂 I have actually been using chick heat plates which I already had from incubating poultry! It works pretty well just to keep the temps above something that would slow the plants right down.
I use a heat mat only during winter here in Sydney and only for my alocasia collection and new plants that I’ve purchased during winter. As we slowly move into the colder season however, I am on a self imposed plant ban since my collection is big enough and have decided to propagate to gift to family and friends. So my heat mat will come in handy for the propagations hehe
great article! your comment about established plants on heat mats was really helpful. i put two plantlets that are in soil on a heat mat hoping that it would help speed up the growth, but they have really been languishing precisely because it was difficult to keep track of moisture levels. going to move them off and see if they fare better, thanks!
Hi, I’ve just found your website. I noticed you have some mesh shelves in the background. I use my heat mat on one of my mesh shelves as it then spreads the heat to that shelf and below. I leave it on a timer 12 hours on. It’s great for propagation of Alocasia bulbs in plastic covered cups. I’ve also germinated Hoya seeds on it, I’ve left them until their first try leaves before moving off. And to root propagations in moss, but a deepish box for that. You can buy a thermostat as an additional item for these seed mats but I haven’t needed to. I’m in the UK and Amazon do them. You have new subscriber too. 🙂
I have only used heat mats to start garden seeds. I couldn’t tell a difference in the rate of germination. They never looked good in the beginning because of the heat either. So I stopped using a heat mat. I also only started them inside my house. I would say if you start them somewhere less controlled then there may be a use for the heat mat.
Hi Memo, I’ve just recently discovered your website and I’m binge perusal the articles 🙂 🙂 I have a question/idea for a next one: over winter the leaves on my philodendron Florida grew much smaller (not so much sun light). Do you think it would be better to chop it (hoping that with more light the new leaves on a mother plant will grow bigger)? I’m also considering giving it a plank to grow onto (rather than a pole). Or would the new leaves come out smaller? Just wonder what is your experience. Warmest greetings from Poland! Kasia