DIY heat mat for seed starting

Noticing that I would have to drop a lot of dough for heat mats, I decided to go with this plan instead: http://www.vegetablegardener.com/item/11658/diy-heat-mat-speeds-seed-starting

Of particular interest is the temperature comparisons of the store bought heat mats and the DIY plan:

Commercial heat mat
Surface temperature
(thermometer placed on top of soil): 73-75 degrees F
Soil temperature: 80-82
Bottom temperature (gap between heat mat and seed trays): 100-102

DIY light heat mat
Surface temperature: 72-74
Soil temperature: 78-80
Bottom temperature: 105-110

Thanks for posting this.
Ingeniously simple, and cost effective.

I once bought a crock pot at a yard sale for a buck or two.
Filled with potting soil, set on "Stay Warm", & used that to jump start tomatoes & peppers.

Thanks for sharing Dennis. I'd better buy up some incandescent rope before congress bans its manufacture

John, that is a great idea. I know where to find a crockpot for about a buck. Thanks!

I have also used a crock pot to keep my starts warm a few times.. tho I used it full of water.One year in a small tabletop greenhouse, inside my other big unheated greenhouse. I found the steam also watered my plants, sometimes too well so I generally opened up one side and turned crock off during the day when it was warm out ..because the larger greenhouse the table was in, was warm enough during the day. I also used it in a cold frame one year for an experiment to start cucumbers in early February right in the ground. For that one I buried it half way into the soil, inside an jumbo oven cooking bag to protect components from rusting etc. We had cucumbers months ahead of the norm.

After only two seasons 2 of my $25.00 Hydro-Farm seedling heat mat stopped working. I'm now using LCD rope light system for the first time this year. It works great. Unlike the Hydro seed mat, it's easy to control the temperature and the heat can be evenly distributed. I bought mine on Ebay, new, Hampton Bay (safe, quality rope lignt) 24ft kit for $19.99 shipped.

Anyone using a thermostat controlled water bed pad heater for seed germination? They're a little more expensive than a LCD rope light, but I think it would work well.

I don't know how common in the US (or what the price is relative to commerical heat lamps), but here I can buy an electric floor heater cable on a mat designed to be buried into tiles for heating a bathroom floor. The one I got last year was 2m x 0.5m (7' x 20") and cost about 35€ ($45). I doubled it over on itself (usable area about 4'x20"), covered it with tiles to distribute the heat, and used a $15 digital thermostat I got on sale to regulate it. The thermostat has a waterproof probe in copper which I stuck into the soil to regulate the heat. I think if I make an actual table with insulation on the bottom so heat doesn't leak out there and embed it in mortar and tiles it would work without folding.

I wanted to follow up that my seed mat is working really well. I average 85 F (which is a little too hot actually...) soil temp with my set up.

Anyone leave the mat on 24 hours a day, or do you turn off your mat when you turn off the overhead light?

I would like to have a solution which works safely outside without mains power. I am trying the muck bed method but it is apparently not overly reliable.

Angelika Maier wrote:I would like to have a solution which works safely outside without mains power. I am trying the muck bed method but it is apparently not overly reliable.

We had great results from our hot bed.

Use fresh horse muck, turn the pile until the heat gets going, I only had about 30 cms depth (which is under what's recommended) I put 6" topsoil on that. Raised seedlings in pots inside a plastic coldframe sat on top of the bed, and then when big enough, planted straight into the bed.  Held 20 C from mid February into May - our last frost is 15th may. I was amazed how the heat just kept going. Biggest fastest Tomatoes/peppers/aubergines I've ever raised. The hardest part was collecting up the muck from the field in cold weather!

Search online for "Victorian Hot bed" lots of resources out there. My understanding is that your muck has to be fresh, and horse is better, though you can use cow muck if its mixed with carbon (leaves/straw)

I use reptile mat and bought water used bed heater mats (2 for $10) . It works great

Dennis Lanigan wrote:I wanted to follow up that my seed mat is working really well. I average 85 F (which is a little too hot actually...) soil temp with my set up.

There is a very detailed how to for the ropelight mat at

https://www.sundaygardener.net/homemade-heating-system-for-seedlings/