Cold frame over raised bed? Earlier harvest in TN?

[mari.beth]

I had a late start on my tomato plants this year because my hubby built two 4x8 raised beds for me which were not complete until mid-May. Therefore, I have a lot of green tomatoes and I am jealously looking at pictures of other people's harvests in other areas of the site. My husband said he thinks he can build cold frames using 80/20 metal and some type of plastic / glass that will fit over my raised beds that I could use next year to extend my growing season and (hopefully) yield ripe tomatoes earlier. I have been reading some on here and other sites about building and using cold frames, but have not seen any that fit over raised beds to be removed after danger of frost. (Maybe cold frame is not the right term for what I want to achieve.) I know that we would need to have some type of door / window on the sides for air flow / temperature regulation and a thermometer so we can assess the need to open / close / cover with a blanket, etc. Any suggestions (type of material, design, etc.) would be appreciated. I also would love any advice on how early I could put the plants in their permanent spots in the raised beds in zone 7a (Knoxville, TN) if I used cold frames.


(I am attaching a picture of the raised beds when I first put in the plants for size /shape reference.)

[rwsacto]

Hi,

Suggest you consider using walls of water (WOW)(Season Extenders) to start your plants a few weeks early next year. You will not need to fiddle with them daily like a cold frame.

I built coldframes to fit in my raised beds, but designed them mostly for late winter greens. They are wood framed foam board with double vinyl tops and automatic lid openers and solar powered ventilation. (kinda geeky). You put a blanket on top when it is too cold, a light bulb inside when it is really cold and a sunscreen on top when it is too hot and sunny. Too much work.

I did not use them at all this past year. Just took the plants directly from the 4 inch pots (after hardening) to the raised beds with WOWs. Ground temperature is as important as sunlight in the early season. WOW will warm the nearby soil without all the fuss and tending of a coldframe and my tomatoes outgrow them in 2-3 weeks. Some use a ring of full 2 liter bottles painted black but WOWs perform better for me.

For the raised bed in your picture, you could also try a small hoop house over the bed using PVC pipe or metal conduit for the frame and sheet plastic for the covering. It would need to be opened every morning and closed every evening, without fail, or you could lose everything.

Again, you are only talking about a few weeks in the spring when this will make a difference.

Hope this helps,
Rick

[mari.beth]

Hi Rick,

Thanks for the advice. I appreciate hearing about your experience with the cold frame over your raised bed.

I have seen the WOW before, but felt skeptical that they would work (there were some mixed reviews). I think I will try them next year. It would be great even if I could get a head start on several plants so I will have some ripe tomatoes while waiting for the rest of the plants to catch up!

THANKS!!!
Mari Beth