Plastic is made from non renewable resources and is probably not something to use in the garden. Clear plastic will get "weeds" to germinate but whether those "weeds" would then freeze depends on your weather and the "weeds". Many are frost hardy and are not killed by frosts and some are cold wehater plants that germinate in the winter and die off during the summer.
A far better method of "weed" control is to deprive them of access to sunlight so they cannot grow by covering them with newspaper or cardboard and another mulch material, to hold the paper in place.

Using plastic will cut the weeding time to just about nothing. Plastic sheeting also cuts down on water loss. Having a barrier against evaporation moisture is crucial to an efficient watering system.

Plastic spread over soil limits the ability of that soil to breath so often the soils become anaerobic. Plastic can cause moisture in the soil to not evaporate which can also contribute to that anaerobic condition.
There is no real benefit to using this material made from non renewable resources.

Plastic will come back to bite you. It works great short term. Then it begins to deteriorate and the weeds grow through and under it. It is a nightmare to try to remove it. Cardboard is great. It stops the weeds and eventually will be part of your soil. Remove the tape though.

kay

I dont' think the OP is talking about using the plastic long term, but more as a little greenhouse. or a little cloach.
I think it will help you sprout more of your weeds at once, whether you get a hard enough freeze to kill them though, I wouldn't bet.
is this a vege garden that you are trying to clean up the soil before you sow? I think it might be worthwhile to try and get the weed seeds germinated and tilled out ahead of sewing.
If it's just an ornamental bed, I think I would lay on a thick layer of uncomposted bark- which will nitrogen starve your seedlings as well as smother them.

This post was edited by lola-lemon on Tue, Apr 2, 13 at 22:58