Interesting comment in Gardening Which (July/Aug) issue – if you find that you are getting too many boys and not enough girls it’s all down to watering. Courgettes, squashes, etc are thirsty plants and to perform well they need a lot of watering (and feeding too). If the conditions are dry the plant conserves energy and produces more male flowers. Too overcome the problem – mulch and increase the amount of watering during the growing season.