I'm wondering what the rule of thumb (or rather, rule of "green thumb") is for Spring planting under row covers. I'm going to be using row covers with 75% light transmittence, which are supposed to raise the minimum temperature 5 degrees. How early may I begin my planting? If it is okay to plant cabbage say, four weeks before the frost-free date, then how do I figure out how much earlier I can plant under row covers? Furthermore, when I am starting seeds indoors, should I start them even eariler if I plan on setting them out earlier under the row covers?
Thanks for any help!

Actually, Allison, I hope you don't mind me adding to this question as I'm considering doing the same. (My seedlings are about to burst out of the pots!) I'm in Zone 9 so that may make a difference. Anyway, I was thinking about using halved 2 liter soda bottles over my transplanted seedlings in about a week or so; to create a sort of "greenhouse effect". If someone could help both of us it would be appreciated. Thanks!!!

You can plant under row covers anytime the soil is workable as long as you plant the correct plants.

Brassicas-Broccoli, cabbage, mustard etc are all cold weather plants and could be planted by mid March in my neck of the woods (SW Ohio-zone 5/6) under row covers such as agripro 19, a light weight type. With 75% light transmission you must be using a 30 or 50 weight

Things that could be planted now under covers are lettuces, arugula, radicchio, peas, cilantro and chard.

Warm weather crops like tomatoes can be started 3 to 4 weeks early under row covers but they usually need the help of wall-o-waters to be successful. I would not try peppers early as they require 750 to 800 soils and will not grow with colder temps.

Scott,

In zone 9 row covers are pretty superfilous for keeping heat in but lightweight ones would work well for pest exclusion on brassicas and eggplant. I suppose you guys do get the occassional frost but crops such as brassicas, cilantro and lettuces like cold weather and a little frost will not hurt anything.

Can you use plastic milk cartons with the bottom cut off in place of row covers?

I haven't tried it, but my neighbor (zone 5) uses them for very early cool crops (tops left off the bottle), and always has salads and early-start warm veggies of a good size.

I've used them in the past, leave the cap off and make sure that you stake them.

I have had my cold weather plants out for some time with lite covers. I have just started picking lettuce and spinach.. I am in zone 6... besides using the lite weight covers I also use frost blankets these are a heavier weight and don't let as much light thru so you have to remove them during the day . We always seem to get those late April early May frost... I just throw a frost blanket over the beds on the nights we get freeze warnings... it saves my strawberry's too..

I have tried something new this year ... it is a flim that has little holes all over it as vents... I set up 4 small hoops 12" high on a 4 x 8 bed and just planted my tomato's on Saturday... the film is to help maintain a 10 degree higher temp...I also used a plastic red mulch to help heat up the soil... at night I cover the film with a frost blanket to help hold the heat in...I had been using the walls of water but I hate filling all those little sections, so I am trying this and hope I don't loose all my tomato plants... my pepper plants are still in the mini green house waiting for warmer soil...