Hi, Can anyone help me with this question? I want to prolong my growing season with row covers (plastic over hoops) and/or cold frames and I'm wondering if the the size of the covering makes a big difference. On the one hand it seems that a larger interior space could heat up on a bright day and maintain a warmer temperature longer but on cooler days ground warmth might be better contained by a low cover. Anyone know if there are any rules about this? I'm hoping to grow some light-frost tolerant crops on into a Toronto December but there are usually a couple of cold snaps (below -5 C) in November that I have to get past. Also, does the plant's distance from the plastic/glass matter in terms of light intensity - say, between 4 inches or 24 inches? Thanks for any information you can give me.