Zucchini Fruit Bulbous at One End: Partial Pollination and Misshapen Fruit
A zucchini fruit bulbous at one end and thin at the other often points to poor pollination. Extension guides tie the shape to how many seeds were set.
The short answer
Iowa State says misshapen squash often comes from poor pollination. The fruit swells only near fertilized seeds. Few bees or poor weather can cause it. UNH Extension suggests hand pollination early in the morning by moving pollen from a male flower to a female flower.
Why do zucchini grow bulbous ends?
Iowa State explains that the fruit wall grows more near fertilized seeds. When pollination is partial the fruit swells unevenly. Virus infected plants may also give small deformed fruit, it adds.
Few bees mean less pollen reaches the female flower.
How does pollination shape squash fruit?
UNH Extension says zucchini has separate male and female flowers on one plant. Female flowers have a small fruit at the base. Bees carry the pollen. Maryland Extension says male flowers open for 1 to 2 weeks before females appear. Minnesota Extension notes the same pattern in cucumbers.
| Option | What it does | Source |
|---|---|---|
| Male flower | Long thin stem | Zucchini Plants Flowering But Not Producing Fruit, UNH Extension |
| Female flower | Small fruit at the base | Zucchini Plants Flowering But Not Producing Fruit, UNH Extension |
| Early season | More male flowers | Growing Summer Squash (Zucchini) in a Home Garden, University of Maryland Extension |
How do you get straighter zucchini?
UNH Extension suggests a small paint brush to move pollen to the female flower. Rolling a male flower onto it works too. Go early, since squash flowers open in the morning and last one day. Maryland Extension suggests deep regular water once fruits form.
A soft brush moves the sticky pollen well.
Troubleshooting
Bulbous end with thin neck: partial pollination. Hand pollinate early in the day.
Flowers but no fruit: only males so far. Wait for females.
Small deformed fruit on a few plants: possible virus. Iowa State suggests removing those plants.
Kind Seed Co shares these plant notes for growers of all kinds. For more on plant stress see environmental stresses on weed plants and underwatering cannabis. Read what roles do bees play in outdoor cannabis for pollinators. See mulch for cannabis for bed care.
Sources
- Why are some of the fruit on my summer squash misshapen?, Iowa State University Extension and Outreach Yard and Garden
- Growing Summer Squash (Zucchini) in a Home Garden, University of Maryland Extension
- Zucchini Plants Flowering But Not Producing Fruit, UNH Extension
- Growing cucumbers in home gardens, UMN Extension
FAQ
Can you hand pollinate zucchini?
Yes. UNH Extension suggests a small paint brush or rolling a male flower onto the stigma of a female flower.
How do you tell male and female flowers apart?
UNH Extension says female flowers have a small fruit at the base. Male flowers sit on long thin stems.
Does weather affect pollination?
Iowa State says poor pollination may come from low pollinator numbers or unfavorable weather.
Can a virus cause misshapen squash?
Yes. Iowa State says virus infected plants may produce small deformed fruit. It suggests removing those plants.
How long do squash flowers last?
UNH Extension says squash flowers open early in the morning and last only one day.
