Germination: soil temp - 75 which is why a heat mat works best and air temp isn't relevant.

Growing on: air temp 60-65 and no soil heat.

Dave

You emailed me about heat mats. I linked lots of discussions about them for you below. Walmart sells them here. So does Lowes and Home Depot once they have their seed starting supplies out. Otherwise many models are available online in a wide range of prices. Most all the seed companies sell one as do any of the sites that sell seed starting supplies. But shop around because the prices vary widely.

Dave

Here is a link that might be useful: Propagation heat mat discussions

That sound ideal. I kinda doubt anyone around here does that. I guess I will have to try some inside the house and some in the GH and see what happens.

Thanks digdirt for that link which should answer any questions about heat mats. I did an experiment recently with my pots on a heat mat. With overnight air temperatures dropping into the mid 40 degree range, I took the soil temperature of four inch and one gallon pots to see the soil temperature with the heat mat at 70 degrees. In every test the soil temperature was within 2 or 3 degrees of 70 degrees. Al

Thanks Al. Yeah even in the GH we have to use heat mats for germination.

Dave