I've never done it before, but have read lots of information on doing just what you're talking about, to get an early start on the planting season.

It can also be done in the dead of summer, to sterilize the soil if there is some type of disease present.

EG

I'm planning on doing this also for the first time. I usually have to wait until after the rains and cold have gone, forcing me to plant later that what I would like. Since I will have raised beds next season, I plan to cover with plastic to warm up the soil and keep it dry. Right now, I have my beds covered in a thick layer of chopped up leaves. I'm going to leave it uncovered until about February. That way the snow and rains and squirrels can help stir up and start decomposing the leaves. I figure one month covered should give the beds enough time to dry out and warm up. Then I'll just scoop off any excess leaves and put them on the compost. I'm not sure about using the plastic after I plant seeds. If I do, maybe I'll only keep it on until I see seedlings, then convert to row cover. I'd be afraid the plastic would fry them. Has anyone already tried this method?

Haven't tried it either, but it is in my plan for spring. I'm going to use clear plastic over pvc hoops for my raised beds in the spring, both to pre-warm the soil and to act as a greenhouse when I put out the plants. I experimented with it this fall, and I think it will help me get a jump on the season. It will likely need to be vented or opened on warmer days though.

I didn't leave the plastic on the beds for the winter because I want to prolong the life of the plastic, and I think it's probably good if the soil freezes over the winter.

That's exactly what I'm thinking, greenbean. Hoop covers to keep the plastic far from the plants but providing protection from the last throes of harsh weather that seem to pop up in early spring from time to time.

peel,
When I used it this fall, it seemed to do a good job of making things toasty warm during the day (so there's a chance things would actually keep growing). I put a thermometer in there, and at night the temps weren't any higher than outdoors, but when I put a blanket under there, it stayed lots warmer. The plants survived until we had a 17 degree night after a pretty cold and cloudy day. This was my cukes, zucchini etc.

Do you mean you put a blanket on the hoop and then plastic over it?

Yes that's how I did it. It would probably work the other way too though I'd guess. It took a few blankets to cover the whole bed. I have one that's an old comforter, that held the heat the best I think.

While I haven't used plastic to warm the soil before planting, I use hoop covers after I plant in late winter/early spring to keep late frosts from killing my seedlings. The covers also help keep the soil drier as we have wet winters rather than frozen ones l CT.

It does help to mulch with black plastic to warm the soil for germination, but I normally transplant seedlings or sprouted seeds at least. Leaving it on all winter may not be the best. I'd research it more before I did it. Though to warm the soil in early spring it would be good for you.

What you're talking about is described nicely in Eliot Colmans Four Season Harvest. It will help you more because he is writing from Maine.

For your winter harvest, you will likely need the added protection of a cold frame. Whereas I can get by with hoop covers.

Hope that helps!

Here is a link that might be useful: Sinfonian's garden adventure

peel,
I just realized my situation may also be different from yours. Here, we have very sunny skies for much of the year -300 days of sunshine they say. I'm just going to guess that CT isn't so much sunnier than northern VT (where I'm from), which is a bit cloudy. Because we live at 7000 feet in elevation, we have very intense sunshine. I just say this because my very limited experience with covering may not be the same other places.

Just FWIW.
Amy

Our soil stays cool enough that having black plastic on it year round would probably be ok except for one week in August. I'm definitely going to try that this year.

I think what I'll do is set it up with plastic in early spring just to warm the soil and decide whether to keep it on once I get to planting time. I'll be able to tell what the weather trends will be by then. If late frosts are expected I'll keep it on to protect the plants.

Of course, I reserve the right to go in the complete opposite direction, too! :)