“Why aren’t my zucchinis producing zucchinis?”
“My zucchini plant flowers but it doesn’t give me zucchinis to eat”
“My pumpkin has heaps of flowers but no pumpkins”
“Why don’t my zucchinis get any bigger before they go yellow and drop off?”
It’s the same old story year after year, I hear it all the time from keen first-time vegetable gardeners. It’s very frustrating to see the hope of future produce, only to be greatly disappointed when your vegetables don’t grow to maturity.
It’s simply a matter of poor pollination.
Cucumber family plants (aka cucurbits) are renowned for this sort of thing but understanding the plant physiology can help avoid the problem.
Cucurbits include zucchini, courgette, summer and winter squash, pumpkin, melons, cantaloupe and of course cucumbers. These are vines that produce separate male and female flowers. Successful pollination of the male and female flower is imperative for the plant to produce fruit that will grow and mature for you to pick and eat.
Here’s a picture of a FEMALE flower. Notice it has a swollen “receptacle” below the flower that looks like a little zucchini. Inside the flower is the stigma, that receives the pollen from the male flower for successful fertilisation, usually passed on by a visiting bee or other insect.
Here is a MALE flower in comparison. Notice there is no little zucchini below the flower and it has a single straight stamen pointing out from the centre of the flower. The stamen contains all the pollen.
You can hand pollinate your male and female flowers by snapping off a male flower and peel back the petals to reveal the stamen. Then, carefully wipe the stamen on the female stigma to transfer the pollen. Use fresh flowers when they first open in the morning, then the male will have plenty of pollen and the female flower will be most receptive. This always works. The only reason that hand pollination doesn’t work is when the flowers are old: insufficient, or poor quality pollen in the male flower or non receptive female flowers due to age.
You can do the same with your melons, squash or pumpkins.
If your fruit turns yellow and drops off, this is due to ineffective fertilisation. Fertilisation takes place after pollination. It might look like the fruit has swollen and pollination may or may not have taken place. The pollen may have been too weak to properly fertilise the female flower. While it might look like you have some little fruit developing, it doesn’t continue to grow and will soon turn yellow and die.
To encourage natural pollination, you need to attract pollinators into the garden. Do this by planting lots of bee attracting flowers. Make sure you always have lots of flowers, with different shapes, different sizes and different colours all year round. Failing that, take matters into your own hands and manually pollinate for better results. And don’t forget to watch out for other problems you can have with leaf eating ladybirds on your cucurbits.