VIVOSUN 2 Pack Durable Waterproof Seedling Heat Mat 10" x 20.75" UL & MET-Certified Warm Hydroponic Heating Pad for Germination, Indoor Gardening, Greenhouse

At first I thought this wasn't even working because it didn't feel noticeably warm. But then after leaving it on overnight under a filled seed tray, I could easily feel the warmth. It's such gentle heat that it just takes a while to get the soil up to temperature, but once it does, it creates a good 15 degrees F or more difference between the soil temperature and the surrounding air temperature. Last year many of my seeds failed to germinate and I suspected that they rotted in the cold damp soil. My house just isn't warm enough in late winter/early spring to get seedlings going. But this product kept the soil pleasantly warm to the touch, and I had seeds sprouting in just two days! Then the seedlings grew like gangbusters in the warm soil--in fact, they grew so fast I had to take the heat away so they wouldn't get too big before it was safe to transplant them to my garden!One tip I learned: the heat is of course going to be highest in the middle of the seed tray, and the cups along the sides that are more exposed to open air will be coolest. So it's a good strategy to plant heat-loving seeds (tomato, pepper, eggplant) in the middle and cool-tolerant seeds (spinach, broccoli, lettuces, radishes) along the sides. Also, since this speeds up germination and growth so much, you might want to plant a little later than you usually would! Otherwise, like me, you might get plants actually starting to blossom in your window in mid-April!

Very happy with these heat mats. I broke the first one (my tray was leaky and I did not know it. It was soaked and stopped working). It initially did work well. I was far more careful with the second mat and it has made starting celery and pepper seeds so far a dream!

These heat mats are the best there is. I have bought more than two dozens in the past few years. They are still functioning as if new.

I count on these for two things. Typically, I use these mats to help me speed up my garden seed germination (and they work like a dream). But I've also found myself using these beneath potted plants outdoors in freezing weather. You can cover trees/plants all you want, but if the roots freeze, you end up with something for next summer's compost pile. Bottom line: great product.

Heating from teh bottom is important when starting seeds or cloning cuttings (heath and heather). For seeds, its perfect. For cuttings, wish it was about 2 inches taller, but it did work out well. The heating pad keeps the correct temperature - just warm and not hot.

Good product. It helps seedling germinate quickly.

I've tried germinating dwarf tamarillo seeds more times than I can remember without a heating pad and within a month of planting them again and using these pads I finally see a seedling.There's no temperature control, it just slightly radiates heat. It's not hot to the touch and while I don't think it's particularly dangerous I don't leave them running when I'm not around either. Like any heating element, I'd make sure it's powered off when not present. But it does the job as basic as it is, and for that it earned the positive review.

This is the second time I have purchased heat mats for my seeds in the greenhouse. Both of them have worked well and performed as advertised. They are durable and just the right size to fit on the shelves of my mini greenhouse and the one I built. The thermostat does very well and kept my seeds from being killed by the recent cold and frost. I recommend that anyone who wants to protect their plants, purchase these warming mats. But make sure that you get a thermostat regulator to maintain the proper heat on the plants.