My husband has a couple of self-watering seed-starting flats that have a built-in container of water beneath them. He tried using an aquarium heater in one of them, with good results. However, in the long run such a setup will cost about as much as grow mats if you don't already have aquarium equipment on hand.

Seeds don't need bottom heat and most cuttings will grow roots without it, just not as fast or with as high a percentage of success. Tent your cuttings and keep in a place with about 70 degree temperature. Remove the tent at least every other day and dry the condensation or reverse the tent to prevent the growth of fungus. Al

Is it the black plastic kind of bottom? Isn't that dangerous and can't the heater melt the plastic?

Al, thanks but I already do that.

I'll share with you what I did when I was looking for a less expensive way to heat the soil. Since this was an experiment and I was concerned about safety all of this was done outside in a safe area with bright indirect light. I used a large but shallow plastic translucent storage box and spread a 100 light set of the small outdoor Christmas lights in the bottom. Then I planted my seeds in a separate container and placed them on top of the lights. It provided just enough heat to warm the soil and germination was fast. I put clear lids on the planting containers and it created a little greenhouse. I removed the seeds to water them so I wouldn't get water on the lights even though these lights were approved for outdoors. The whole set up was about
$5.00 and I started lots of seeds this way.

So you just put the lights right in the storage box on top of nothing and then the plants right on top of those? I've heard of doing this before but with the lights in a layer of sand.

It sounds like a really cool idea. Maybe I can find some on Freecycle.

There was a time when thrift shops had a lot of blankets and heating mats for beds and stiff backs and the like and they were quite cheap. I have heard that thrift shops a quite the fad now and they are not so inexpensive. Perhaps someone with recent experience could comment on thrift shops.

I just discovered another thread on cheap alternative to buying a heat pad.

I think I'll go with the heating pads I got then. The kind you use for aches and pains.

I am a newbie trying to grow plants from seed and did try high and low to find info about a cheap AND safe way for seed heat mats. I don't remember in which forum I read it but someone raised the question about how much electricity the "human" heat pads are burning versus the seed heat pad. The initial investment might be lower but who knows how much you will be paying for electricity in the long run. So, I am going for the seed heat mat. I know, it will make a deep dent in the seed budget. Besides, I am also considering the Murphy Law. Call me Chicken!

Because I start a lot of cuttings and do not heat my greenhouse I needed a large heat mat. I ordered a heating cable used to keep rain gutters from freezing. Forty eight feet long using 300 watts of electricity. I epoxied it to a 3 by 6 feet foam pad one half inch thick. From a salvage yard I bought a 3 by 6 foot ten gauge aluminum sheet which I set on the heat cable and foam. I connected a variable thermostat to regulate the temperature. My containers set right on the aluminum. I have been using it for several years. Al

When we garage sale or thrift shop, we keep a eye out for heating pads for water beds. Works great, and the oldest one we have is almost 12 years old. So they do last and they can take getting wet.

Great idea!
I like that they have thermostats.

ms_minnamouse: I use rope lights and christmas lights.

You may have seen it.

rope light bottom heat

I use two containers nestled inside the other. The lights go in the bottom container. The tray goes in the top one. I can get one tray in a sweater box. They come from Wal-Mart and cost about $5 each.

Thanks, I really like that idea too. I'm sure people will be offering them on Freecycle after the holidays. I'm also setting up a growing shelf in a chilly basement. I think stringing some of those lights in it might help keep the temp up since the lights are cool running.

Thanks, I really like that idea too. I'm sure people will be offering them on Freecycle after the holidays. I'm also setting up a growing shelf in a chilly basement. I think stringing some of those lights in it might help keep the temp up since the lights are cool running.

That's mine. It's easy. Tomorrow, I plan to move most of those plants out into the cold frame. I finally got it covered this week and the soil in the raised bed is nice and toasty.

I used it this summer to do cuttings. I tried outdoors, but I wasn't getting much success. With this method, I have about 60% success rate. I think my problem has more to do with sterilization than anything else. I'm also using it to start some biennials. Once they're up, they'll go into the cold frame too. I did find that I needed more heat than when propagating, so I just put a strand of Christmas lights in each box. 50 lights per box gives me about 75-78 degree temps in a 50-60 degree basement.

The rope lights are a little over 60 watts of power.

what do you think about using a heat lamp underneath the pots? aim it up toward bottom of pot. if it gets too hot use a timer so two hours on one hour off?