Can plants grow well under 4 millimeter plastic sheeting.?
Ventilation will be important. It can get hot under there. Don't know if you are talking a greenhouse, grow tunnel or what.
Yes but what ever you do make sure the sheeting does not touch the plant. In winter it can cause frost damage and in summer can burn the plants.
Yes but if you haven't bought it yet make sure you get something that is resistant to UV rays, it will last longer.
