I have had regular outdoor gardens for years, my zucchini would have been producing for a month already/ This year I am doing a tunnel garden, the plastic cover is ultraviolet resist for it lasts longer, the typical semi translucent poly. My zucchini and yellow squash for past month will only put out male flowers not female. I know they start out with male but this is excessive. I planned to hand pollinate but have no fruiting female flowers only male flowers. Would this be related to the light being filtered? Has anyone else had this problem?? Cucumbers do fine. I pulled up the darn zucchini and am planting green beans which also do fine. but I am puzzled. I had read a book by the pioneer of lighting, Dr Ott years ago and he mentioned specific plants that would not either mature a fruit, or bear under greenhouse glass. Help!!