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.
Hi pointy1, I'm afraid there are no rules when it comes to cold frames and hoops - you go ahead and make a rule, and Mother Nature will come along and throw it all out the window. There are a few thoughts on plastic, and if it's actually the best covering, due to it's unfortunate habit of moisture condensing and then dripping onto plants. I think if you can vent the cold frame to avoid the condensation that's best. I've had some success with making a frame out of hay bales, filling it halfway with fresh horse manure then covering with glass - old windows in wooden or aluminum frames. You can plant into some soil on top of the horse manure, or plant into pots. There should be at least a couple of inches air space between the glass (or plastic, should you choose to use it) and the foliage of your plants, because they will rot/freeze if too close. There is little to no difference in light transmission. This is actually a hotbed, producing it's own heat via decomposition of the horse manure. As to the size of your tunnel/cold frame, in most cases if you're building it on an existing bed, the size of your bed will dictate the size of the tunnel. I pretty much go with a longer (up to 20') bed that's narrow enough to reach over (3-4' wide) and you'll find that most items you can easily find - ie: rebar covered with pvc pipe, plastic film, row covers made from spun bonded polyester etc, fit these dimensions. Height above the crop will depend on how big that crop gets. I usually allow about twice the height of the crop to decide on how tall the tunnel should be. Hope this helps, let us know how it goes.
Thanks for your reply. I'll guess I'll just try a couple of methods this year and see what works best. The hot bed sounds great but I haven't got enough room for that where I am, nor a ready supply of manure. I've since come across some interesting information in Eliott Colemans "Four-Season Harvest". Thanks again.
