I don't know about this but a guy in the local nursery uses electric blankets you usually put in your bed. I didn't do that because it seems unsafe to me.

I would not advise overlapping heat mats, nor using electric blankets.

For years I used regular heating pads with no problem, and now my husband uses them to make warm beds for the cat outside in the cold. (I wouldn't advise that either!)

Every time I asked that question in a forum, I was asked if I was willing to take the chance of starting a fire with the heating pad, and I realized that I was wanting to take the chance of a fire stating. The same thing with overlapping heat mats...What were you thinking? They will get very hot, possibly melt the plastic, and who knows what else?

If it were me, I don't think the price of a proper heat mat, used properly would be as expensive as losing my home, or even having a portion of it burned.

I think I have found a solution. I have a few mesh plant trays. I will put them across the width on the part that has to be overlapped and a 2 x 4 0n the other end. I will attach a painted 1/4 inch masonite on top of the 2 x 4 and let it rest in the trays. This will raise one end up by a little less than 2 inches and the mesh trays should allow for the dispersion of excess heat. Since I have 2 light fixtures, side by side, with a 13 inch span between the fins of each fixture it should also provide enough light if 1 is a bit lower than the other. If it doesn't I can always cover the gap with mylar or tin foil.

outside the box ... you could have them on two different timers... and switch them off and on... opposite each other ...

ken

Have you considered adding little 2 or 3 inch pots of seeds on the excess mat area? They will grow toward the lights but you can turn them easily. I'm always looking for more starting space.

That is one item we don't need here in Miami. Our seed starting date is just before the summer heat breaks.

Doesn't anyone sow all of their seeds in germination flats? I sow hundreds of seeds in each flat, and only use three or four for all of my needs. Thus, I need very little real estate devoted to bottom heat.

Once everything has germinated, the heat is unplugged, and the transplanting into cell packs process begins. I only grow 8 or 9 hundred plants these days, all transplanted into less than twenty cell flats holding 36 or 48 plants.

Once transplanted into the cell packs, all I have to worry about is light!

I strongly urge everyone to use heating sources meant for this purpose and NEVER heating pads or electric blankets. You've got heat mats of varying sizes or heating cables (my choice) buried in the germination flat.

I've attached a little slide show that illustrates this option. I'm using it only for the pictures and have nothing to do with the company. I've never done business with them.

Here is a link that might be useful: this might be interesting

Thanks for the link Rhizo. That was a good tip about Chamomile tea to stop damping off!

I sow all my seeds in repurposed mushroom boxes. That way I can keep each variety and or color separate. 8 mushroom boxes fit perfectly in 1 tray but I usually have 3 trays full when I'm starting my seeds. I don't like to crowd the seedlings.

I do use Chamomile tea for damp off but I also use cinnamon which does the same thing.