Hoop House Gardening

Ok. So, Spring is really just around the corner (thank God). And, is there anyone out there that would like to share anything regarding starting seeds in an unheated hoop house greenhouse. I'm thinking about starting veggie plants and some annuals to sell at the end of my driveway for a few bucks. This past Fall, we built two raised beds and grew spinach, loose leaf lettuce and brocolli, cauliflower, brussels. But, we were infested with some kind of fly that laid eggs and also green caterpillars that just ate and ate til there was nothing left. I'd like to stay organic if possible. Any suggestions from anyone?