Many vegetables require both a male and a female flower to be present for fertilization. Zucchini are no different. The good news about Zucchini is the male and female flowers are very easy to differentiate.
Male flowers, that tend to be much more common in a new zucchini plant, have a fairly thin stem while the female flower will have a small Zucchini beneath it.
Male Flower
Female Flower
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