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Plant diseases
Poor fruit set
Also called poor pollination (widely).
Illustration
Baby zucchini and squash that shrivel and drop off, or rot, while still small, because their flower was never pollinated. Waiting out the first male flowers, protecting bees and hand-pollinating in the morning fix it.
How to spot it
- Tiny fruits behind the flowers that shrivel and drop off, or rot while still small.
- Fruit that swells at the stalk end but stays thin or misshapen at the flower end, which may shrivel and rot.
- Plenty of flowers but no fruit early in the season: plants open only male flowers for the first week or two.
- Female flowers have a tiny fruit behind the petals; male flowers sit on a long, thin stalk with none.
- Worst in cool, wet weather, in great heat, or where bees are scarce.
Easily confused with
Blossom end rot
A dark, sunken, dry patch at the flower end of fruit that has kept growing, rather than small fruit shrivelling whole.
Choanephora fruit rot (wet rot)
Fuzzy growth on old flowers that spreads into the fruit, which turns dark and mushy, in warm, wet weather.
Mosaic virus
Fruit with bumps, rings or blotchy colour, usually with mottled leaves.
Where it's a problem
- Worldwide: Common everywhere, especially early in the season and in cool, wet spells. Not regulated.
- Australia: In the hottest weather, plants often open many male flowers and very few female ones; plantings that flower in cooler weather can do better.
What to do
- Be patient early on: the first flowers are male, and no fruit forms until female flowers open.
- Take insect netting or covers off once plants flower, so bees can reach them.
- Keep the soil evenly moist while the fruit sets and swells.
- If few bees are about, hand-pollinate early in the morning, as each flower lasts only a day.
- To hand-pollinate, pick a male flower, strip off its petals and dab its pollen onto the centre (the stigma) of an open female flower, or move the pollen with a small soft brush.
- In a cool or rainy spell, wait: fruit set usually picks up once the weather improves.
- If it happens every year, choose kinds that set fruit without pollination (sold as parthenocarpic).
Spraying won't help fruit set. Official guides advise against spraying pesticides while plants are in flower, as it can poison the bees that pollinate them.
Vegetables it affects
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Sources
- University of Maryland Extension: Growing summer squash (zucchini) in a home garden
- University of Maryland Extension: Key to common problems of squash
- UNH Extension: Zucchini plants flowering but not producing fruit
- RHS: How to grow courgettes
- Gardening Australia: Cucurbits
- RHS: Courgette, marrow and squash problems
Facts checked Wednesday 21 October 2026. General guidance only: follow your local council, agency and product label.