Depends. Do you want to completely cover, and cook the plants underneath? HD has 6mil poly to do that. If you want to raise the temp a bit but not too much, Territorial has a nice one.

Dan

Thanks. I had never heard of Territorial until now and I believe they have what I'm after.

Ron

Get some of their lightest weight row cover too while you're there, to ward off the critters - ~90% light transmission; I have row cover over my eggplant in anticipation of flea beetles and some on one side of hoops for wind protection.

You can also combine a remay/lightweight-type row cover with the plastic to give you a couple of extra degrees in the fall or spring to extend the season. I use plastic with a heavyweight row cover to get me to about 26ºF.

Dan

Have you tried the stuff with the holes punched in it? I like the idea to keep the heat down but wonder if it allows too much cool air inside.

Ron

I have some, from Territorial. It will raise your temps several degrees, but I found here on the Front Range that the wind is too strong for that product alone unless I partner it with row cover on the sides of my hoops. If your soil is warm you shouldn't have to worry about too cool under there. I forget who - maybe Burpee - has a plastic with slits in it that allows a tad less heat to escape at night but even a 6mil poly won't capture that much heat (~R.6 - 1) but at least it keeps the frost off. If you're concerned about it, you can take clearish 1 gal milk jugs, fill with dark-colored water, and put them under the hoops for more heat.

You'll also want to watch the center height of your hoops with 6' widths, as you may not have enough left to anchor the bottoms (e.g. 2' high).

Dan