Heat Mat / Seedling Mat Questions
 

So, I'm shamelessly searching for mentor advice on this one - I have reached the point in my collection where I have a fair number of intermediate/warmish orchids and they grow in the same space and in the same temperatures as the rest of my orchids. I am concerned that I am stunting the growth of the warmer growing orchids because of my nighttime lows here in the frozen northeast.

In the winter, that means 70f days and 58f nights (give or take a few degrees in either direction). It hasn't been an issue in prior winters, but now the collection is larger and more diverse and I'm wondering whether a heat mat (seedling mat) might help keep the nighttime lows from getting too low.

I have read general notes here and there that people use heat mats for their warm growing phals in the winter with great success. But what does this entail exactly? Do you simply plug the mat in, place the phal pot on the mat and walk away? Is the mat on a timer and it kicks on at night? Is the mat on a thermostat and kicks on when temps drop? A setup like this could only affect the root temps of a potted orchid, what do you do for the foliage?

Aside from the set-up questions noted above, my real concerns are fungal / bacterial. If you're artificially raising the temp of the pot, roots, potting material, etc., and you're watering with the same frequency (or perhaps greater frequency due to the temp increase), aren't you creating the perfect warm, dark, moist environment for a fungal / bacterial explosion? Do all heat mat users prophylactically treat with Physan or its equivalent?

Here's what I was thinking:

Amazon.com: Hydrofarm MTPRTC Digital Thermostat For Heat Mats: Patio, Lawn & Garden

Together with:

Amazon.com: Hydrofarm MT10006 9-by-19-1/2-Inch Seedling Heat Mat: Patio, Lawn & Garden

If anyone has experience with this type of set-up, I would really appreciate your thoughts. Thanks, in advance.

- J

Heat mats are really great. Yes, basically you plug in place orchids on top and walk away. I think it's better to place the mat under the tray to avoid damaging it in the long run.

Bottom heat is actually ideal for growing plants. In fact, that's what many professional growers do (all plants, not just orchids), via a network of hot water circulating in tubes either under the ground tarp, or under the tables.
Why?
1) Plants do much better with warm roots, it stimulates their growth.
2) It reduces the costs of heating the air in the greenhouses. If the roots are warm, the foliage will easily tolerate lower a temperature.

As to your concerns over disease, just like with 'normal' growing, good air circulation is the key!

I don't have mats, though I want some, so I can't tell you more about actually using them.

Just about a month ago, I set up a new shelf in my greenhouse to make a slightly warmer environment for some of my cattleya seedlings and a few warmer growing plants. The greenhouse in winter is heated to 65F in the day and 55F at night. I have found young plants suffer a bit (for me) in past years. So I put seedling mats on two shelves. I run them full time and they don't get excessively hot or anything. I then put my plants on them. And then I used a silver survival blanket to put on the top and around 3 sides of the shelf to keep in extra warmth. They are just cheap Coghlan brand thin blankets that cost a couple bucks at a sporting place. I have a T5 light for each shelf. This arrangement has raised the day and night temps by about 6 degrees and the seedlings seem to love it. The roots are really growing. I need to water more often as the warmth does dry them out quicker. You can just see new roots starting everywhere. Most of those are potted in fine bark and there is no fungus issue of any sort. I am so happy I moved them to this little warm chamber and think they will be ready to bloom sooner because of the growth they will have this winter. I do have a small fan running as well and the open front is open to other fan breezes from the rest of the greenhouse. I set several dishes of water on the shelves too for humidity.

I have used my heat mats a lot, both for day and night temps. I even have them under my converted fish tanks and never had a problem with fungal or bacterial disease. When they are on, I make sure to increase the ventilation. They are ideal to manipulate a temp. drop at night time. I've started doing this when we moved from a cool NW facing location to a warm, west facing apartment. I have a thin layer of styrofoam under the mat, and make sure not to squish the cord. I don't particularly like 25-28C in the house, and this allows me to be comfortable and the plants to grow. When it gets really cold, I put the bigger plants on a spare one in front of the window.

A typical seedling heat mat boosts the root zone temperature by 10 to 15°F, so you will still have day and night temperature differences. I wouldn't worry about that so much.

I recently had an experience with one of the relatively inexpensive Hydrofarm 17 W seedling mats (that fits inside of a typical nursery tray), finding that it had been submerged in water for over a year. When I let it dry out and then plugged it in, it worked perfectly, so I wouldn't say that's too much of a concern either and you get more direct heating that way.

I put my plants directly on the mat since it is vinyl or something similar and just wipes off. I really see root growth with them. Hopefully the leaves and PB's will respond also since there are so many roots to support them. When I say my temps increase by 6 degrees, that is the ambient air in the shelving unit with the front completely open to a cooler greenhouse. So the roots are likely a lot warmer than that being on the mat itself.

Just to clarify a bit: I put the styrofoam on the bottom to protect furniture, and the fish tank or plants directly on top of the mat. Sorry for the ambiguity.

This is all very helpful. See, all you have to do is ask and the mentors come out in force! I love the OB. Looks like there may be a heat mat under the tree this Xmas.

Thank you all so much.

-J

Confirmed. Early reports have spotted Santa with a heat mat. :)

- J

This has been a really helpful discussion! I am currently looking at utilizing the heat mat for some of my orchids as well and have found a lot of useful information here!
I still have one question though (probably a silly one :D), hope someone can help me.
So, the question: is there a good way to combine the heat mat with the humidity tray? Will it work if I put the mat under the tray, will the plants get any heat then at all?? Or if I put it above the tray I believe the tray will not give anough humidity to the plants anymore... :scratchhead:
Does anyone have any ideas?