I could never figure out how my brother and sister-in-law grew such a hugh amout of tomatoes, and they are still growing. Well I finally asked them, here what they said. They bury gutter heat tape under the soil and leave it on. They get an early start, and a late finsh. I live in Palmer, Alaska and it's now Sept 24th and they are still growing tomatoes. you need to buy gutter heat tape only, you can get it at lowe's or home depot and it comes in different lengths. so I'm going to do it. You can bury it below the dirt. They didn't just bury it in one length. they kind of made a s shape out of it under the dirt. they have raised boxes in their greenhouse. and they didn't do that with the other box they have in their greenhouse, for growing cucumbers. It sits on the floor and they had a bad year for their cucumbers. So next year they will also raise the box and put in gutter heat tape.