I am wondering if those seed starting electric mats that warm to ten degrees above the room temperature use a lot of electricity? Do you consider them safe to use?

We use one and we love it. It's entirely waterproof and perfectly safe to use.

You can't place it right on a countertop since the counter will suck away all the heat. What we do is put a terrycloth towel down first, then the mat on the towel, then the seed trays on top of the mat. Works great!

I put mine on top of salvaged styrofoam sheets in my GH. I love them! Much less expensive to heat the seed flats than try to heat the entire room! The small ones only use 17W, less than using a lightbulb.

Thank you both, I ordered two of them from a garden catalog now I will feel confidant using them. The tips will be helpful when using them. My DH built a light table for me which he covered with formica to make it easy to keep clean and waterproof so I should be ready to put it to use.

I found some 2' x 2' squares of drywall / plasterboard at Home Depot for $4-5 each. I think that's an even better insulator than wood. Putting the heating mat on top of that directs all the heat upwards.

(I covered my heating mat with plastic film even though it is waterproof - "just in case".)

What's harder is to keep the heat from escaping upwards in a draft and by evaporating water from the seedling tray. A humidity dome helps, but if you have excessive water, it will evaporate, condense, drip down, re-evaporate and so on, carrying heat away with every cycle.

But you don't need to trap ALL the heat - and if you did, you might make the soil too warm for seeds like lettuce that need it cool.

Ok Rick, I will keep everything in mind that you posted. I have seed starting kits from both Park and Burpee they all have covers that I can use or not will see how it goes. I have used the Burpee kits before for starting annual flower seeds they worked pretty good. The Park ones are new they use the sponges the seeds germinate in so that will be new to me. I will be starting flower seeds no vegetables, the few veggies I plant are purchased plants from a local nursery. Guess I will have a learning experience with the new products I purchased for seed starting. These are the ones I have. http://www.burpee.com/seed-sta...

http://parkseed.com/parks-orig...

Dave and Woofie said the most important things. A towel or some plywood are probably 90% as good as drywall.

One thing: as soon as any seedlings emerge, you really DO wnat to remove the humidity dome. Those domes assure 100% humidity and still air, which is almost a guarantee of damping off.

Sometimes, if half the tray has emerged but the other half hasn't, I'll remove the humidity dome but drape some Saran Wrap over the half of the tray that has not emerged, to keep those seeds moist. I use 2-3" lengths of mini-blind slats cut thinly into halves or thirds lengthwise to support the film up off the soil-less mix (just in case touching the soil is a Bad Thing).

Usually when I start seeds in plug trays, I cut those trays into 4-5 "slices" and plant all one seed type in each slice. That way, I can re-arrange the slow germinators to be together under a dome or plastic film.

Good tips that will be useful.

Heh, I don't go to the extremes that Rick does. I just take the domes off during the day, and put them back at night. But, then, my flats are in a greenhouse, so that's more about keeping them from getting too hot during the day, or too cold at night.

I use them in my makeshift shelving unit greenhouse in the basement and spill water on them all the time--no problems at all. If you set them up in the basement, too, just don't have your basement flood during a storm and run down to unplug the submerged surge protector while standing in five inches of water.

I also learned the hard way that I didn't need heat on every shelf and not to keep the bun rack cover zipped up at all times. No, I didn't take a hint from the condensation covering the inside. Nor did I realize the thermometer I stuck in there reading over 80 degrees was trying to tell me something whenever I unzipped the unit to check on seedlings that were turning yellow--also trying to tell me something--even though their trays were dry (all the water was evaporating and condensing on the inside of the plastic cover!).

So now I turn one large mat on under the lowest shelf of seedlings that needs heat (pansies for example don't) and zip it up. The zipper on the plastic cover came loose from the plastic on one side, so there's a natural air hole that prevents vapor and too much heat "naturally" now. Heat rises, so it's always warm enough top to bottom, but still warmest at the top. I put the warmth-loving plants closer to the top and everything else in the middle and bottom shelves.

lovesblooms said:...
I also learned the hard way that I didn't need heat on every shelf and not to keep the bun rack cover zipped up at all times.
...
So now I turn one large mat on under the lowest shelf of seedlings that needs heat (pansies for example don't) and zip it up.
... Heat rises, so it's always warm enough top to bottom, but still warmest at the top. I put the warmth-loving plants closer to the top and everything else in the middle and bottom shelves.

Genius! And simple.

Everything should be made as simple as possible, but not simpler.
- - Albert Einstein

OK folks, I'd like to revive this thread with the question that's been stopping me from trying to start seeds:

I have room in the basement ONLY.
The temperature fluctuates wildly down there.
Descriptions like "10% above room temperature" are not really helpful when the seeds I'm trying to start want to be a certain specific temperature/range.

Is there NO system available where you can dial in what you want the temperature to BE, steadily?

I've been browsing around for years and have never seen one.

Best thing I can think of is an aquarium heater, rigged up in a big tub of water into which I can partially submerge another container with my seed trays in it.

Thoughts?

Well, there is a thermostat you can plug those Hydrofarm mats into (and I have one), but my experience is that even though the instructions say you can plug in multiple mats, it does NOT work well for more than one. Even when the mats are the same size. It did work fine for just one large mat, tho. I used it with one of my 4-flat mats and it did pretty well, although the edges do stay a bit cooler than the middle.

I had no idea - let me look that up!
I really thought I'd be out of luck - thanks!

Oh, hey, they have a digital one now. Mine is just an old one with a dial. Looks like the digital one is less expensive now, too. I may have to try one myself!
https://www.amazon.com/dp/B000NZZG3S/

Is this what you mean by "large" mat?
https://www.hydrofarm.com/p/MT...
I have an old dresser down there to use as a table - the top is pretty much that size.

We cross posted.

Well that was so quick and easy I'm embarrassed I hadn't found it myself while poking around!

Thanks for pointing me there!

Yes, that's the one I have, just couldn't remember the dimensions. It will just fit 4 standard 1020 nursery trays. I have two of those and several of the smaller, single tray mats. What's odd is that 4 single mats use less power than one large mat. (The single ones use 17W each and the one big one uses 107. Weird.) I put a layer of styrofoam underneath the mats to help conserve heat.

cool.
Thanks!