The problem is that the fruit are not getting pollinated. This job is normally done by bees, but for some reason this year they’re not doing it. I don’t know why – we still see plenty around the garden. Strange.
So, I’m reduced to doing the job of the bees by hand-pollinating zucchini flowers.
The basic idea of hand pollination is to transfer pollen from a male flower onto the female flower. This causes the seeds in the immature fruit to become fertile, and so it grows to maturity in order to perpetuate the species. If the seeds aren’t pollinated, the plant isn’t going to waste energy growing a non-viable fruit. It just withers and drops off, and the plant tries again with a fresh flower.
The best time for pollinating zucchini flowers is in the morning, when they’re fresh and just-opened. Later in the day the heat starts to wilt the flowers and dry them out.
So how do you know which flower is male and which is female?
The male zucchini flower has a thin stem, and a single pointy bit inside it (the stamen) covered in dust-like pollen.
The female zucchini flower has a small fruit (ovary) behind it instead of a stem, and a more complex internal structure (the stigma).
Some people use cotton swabs or artist’s paintbrushes for pollinating zucchini flowers, but I’ve found the simplest way is to simply pick the male flower (don’t pick the female flowers!), peel off the petals, and use it like a paintbrush to dab pollen onto the stigma of a female flower. Quick and easy.
**Update:** I’ve posted photos of hand pollinating pumpkin and squash flowers, which is a very similar process.