Today 
Poor early-summer weather, with a prolonged cold spell, and few insects results in poor pollination. This means courgettes fail to develop, and they quickly rot on the plant. However, this is only a temporary problem, and once the weather starts to improve, so then will the crop.
Solution
Organic
Pollinate the early batch of flowers by hand, rather than relying on insects. Pick an open male flower (which doesn't have a swelling at the base) and strip off the petals to expose the stamens and pollen. Then just rub them thoroughly against the stigma of a female flower (which has a swelling or an immature fruit at its base).
Watch Monty Don plant out courgette plants in our video from the Gardeners' World garden at Berryfields.
