It’s a common problem: squash plants look healthy enough, and have been flowering, but just won’t produce any fruits! We’re going to get to the bottom of why this happens, and show you what to do about it.
Male and Female Squash Flowers
The first thing to point out is that squashes (and all types of cucurbits, whether they be melons, cucumbers, pumpkins or zucchini) produce both male and female flowers. So while both sexes are found on the same plant, because the flowers are physically separate they can’t self-pollinate and absolutely must have the assistance of pollinating insects in order to transfer the pollen from the male flowers to the female flowers.
You can tell the flowers apart by looking immediately behind them. Male flowers are attached to the plant by a simple straight stalk, while female flowers have a distinct bulge behind them – this is the ovary that must be fertilized if it’s going to mature into a fruit.
Now what tends to happen when flowering gets underway early on in the summer is that plants put out lots of male flowers but very few, if any, female. This may happen for a few weeks and anywhere up to a month. But don’t worry, it’s completely normal! There’s nothing you can do about it other than wait, and eventually they will begin producing female flowers too.
Encourage More Squash Flowers
If after a month or so plants are still producing only male flowers or very few flowers generally, despite plants looking healthy, then the culprit is likely an imbalance in nutrients. Excess nitrogen will encourage lots of leafy growth at the expense of flowers. Either reduce the amount of nitrogen you are applying in your feed, or switch to a feed with a higher concentration of potassium, which should encourage more flowers and, hence, fruits. An organic liquid tomato feed is perfect and could be just the boost your plants need to get them flowering.
Another reason for sporadic or poor flower production is hot or dry weather, which can stress these typically thirsty plants. They’ll be more interested in conserving their resources in order to survive than pumping out flowers and swelling water-intensive fruits. The solution, of course, is to keep plants well-watered when it’s hot and dry, so they aren’t left wanting.
It's important to water deeply to make sure moisture reaches right down to the roots. If you find that the water runs off the surface of the soil you can mould soil into a levee right around the plant to trap the water and give it time to sink into the soil where it’s needed. If you have the space, let trailing or vining varieties of squash sprawl along the ground so they have the opportunity to sprout more roots along their length. They will do this whenever a node – from where the leaves emerge – touches the soil. More roots mean the plants can suck up more moisture and more nutrients, making them more resilient in the face of both challenging weather and pest attacks.
Pests That Love Squash Flowers
It’s worth checking the vegetable garden daily if possible to see how everything’s doing. This also allows you to inspect plants for pests. Squash leaves are usually thick and robust, and they rarely suffer damage from pests like slugs and snails. The flowers, on the other hand, are soft and basically irresistibly delicious, which makes them an easy target for these pests, as well as other nibblers like deer and rodents like rabbits. Do what you can to evade these pests, particularly the slugs – and especially in wet weather!
Squash plants produce both male and female flowers, so in theory one plant is enough to ensure pollination. But from experience I can tell you that pollination and fruit set is so much better if you have more than one squash plant growing in the same area. Two is great – three, four or five is even better! This way you’ll have plants at perhaps different stages of growth and in different patches of soil, which should encourage a range of flowers at different stages – so hopefully there will always be enough male and female flowers in bloom at the same time.
In some cases you might have plenty of female flowers but then the developing fruit never really gets underway and instead just starts to rot at one end before simply dropping off. This is usually because the female flower just wasn’t pollinated or wasn’t pollinated enough. Perhaps there aren’t many male flowers about to ensure a good supply of pollen, or maybe there aren’t enough pollinating insects around to do the job?
Including more flowers in and around the productive plot will help with improving rates of pollination throughout the garden, because it will draw in more insects. But sometimes you need to take matters into your own hands – literally! Look for a mature male flower that’s just opened or is on the very cusp of opening. Detach it, peel back the petals to expose the pollen-carrying stamen, then gently rub it back and forth onto the stigma at the center of the female flower. Do this earlier in the morning, if possible, when the flowers are at their most receptive. And that’s it!
You can also hand pollinate using a fine artist’s brush to transfer pollen from male to female flowers. Using a brush works best on smaller flowers like those of cucumbers.