Seed Heating Mats for Starting Seeds Indoors

I did a little experiment. I started my lettuce bowl, putting seeds on the ‘bowl’ and lightly covering with sand. I didn’t have enough room to put the whole bowl on my seed heating mat (I’ve ordered another one) so I put half ON my mat and half OFF the mat as in the picture. The heat comes from the bottom. The temperature of half ON the heat mat was 77°F and the half OFF the mat was much cooler at  70°F. The half on the mat germinated in 3 days while the half off the mat had only a few seeds germinate. Amazing how the temperature affects the germination rate. Lesson here? If you plan to start seeds indoors, get a seed heating mat. Next: Review of my Seed Starting Class last Saturday.

One comment on “Seed Heating Mats for Starting Seeds Indoors

  1. gene solyntjes says:


    Thanks for this information concerning your seedling heat mat experiment. When you complete your greenhouse you will discover your seeds will germinate outside at a ground temperature of 47 degrees here in the high desert in northern New Mexico. With a min/max thermometer you will find the temps will swing at this time of the year, with no external heat source, from 100 degrees ( air temp at the roof apex of the GH) to about 12-15 degrees at night. Ground temp will be about 47-50 degrees.

    The seed germination % is of course less than when being germinated inside in a heated environment, but the germinated seeds do not have to be transplanted. I am just learning all this after reading the Coleman “4 season” gardening book. I am happy its working for me.

    I congratulate you on your growing skills. Do keep us informed, you area wonderful source of gardening information.

    Gene S.


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