What is a hot bed? I don't heat anything, just put the containers out and let nature take its course. You really don't want to get sprouts before they can survive naturally in your area. If I want something early I sow it inside. For most everything, however, I put the seeds in the jug, put them out in the cold and that's that.

I'd take the tops off during the day if it's routinely getting into the high 60s or 70s. What are the night temps? If they're also well above freezing then you probably don't need the tops at all. Also, what are you growing that it's five inches high in less than a week?

I think you might have better luck asking this question in the greenhouse forum.

This forum is for winter sowing - we plant our seeds in the middle of winter and let them sit out in the cold and snow until they naturally sprout. We don't use greenhouses or hothouses or cold frames. Just mother nature and a milk jug.

Here is a link that might be useful: greenhouse forum

Thanks for the info. The plant that has gotten so big so fast is a Brazilian Morning Glory.