I'm confused about zucchini. There were male flowers on the plant before the female flowers appeared, and male flowers are still there. I know that zucchini come from the female flower; I have one zucchini whose flower has fallen off, and another whose flower appears a bit withered. Does the zucchini appear BEFORE fertilization, then? If so, how do I know if the zucchini is fertilized and ready to pick?