Why do some of my zucchini shrivel and turn yellow at the blossom end?

Question

Every year, I grow a zucchini plant, and every year a few of the zucchini stop growing once they reach a few inches in length, then turn yellow from the blossom end:

Left to themselves, they will start to turn soft and shrivel, again starting at the blossom end. I generally pick and dispose of them once I notice them.

Other than a few zucchini that don't develop properly, the plants themselves are generally healthy and usually have healthy ones forming at the same time.

What causes this, and what can I do to prevent it?

Answer 1

If the blossom end turns black, that's blossom end rot, due to irregular water supply disabling calcium uptake, but the other cause of this problem is the female flower, particularly when the weather is wet. The flower traps water and causes the end of the burgeoning zucchini to start rotting. It usually only affects some of the fruits, and a way round it is to carefully remove the flower once you can see the zucchini is starting to grow away nicely, but when it's still small.

Answer 2

If it happens when they are very small then it is just an abort. It happens to some varieties more than others. A little bit bigger (flower opened and closed), they could have pollination problems or a problem with inconsistent watering. I haven't noticed a problem with BER with zucchini.