Why Are My Squash Fruits Rotting?
A young squash fruit that turns yellow or brown and rots at the tip is often poorly pollinated, particularly in damp weather. Fruit can also decay when it stays wet or lacks airflow. Check the flower end and growing conditions, then improve pollination and keep developing fruits drier.
First, identify whether the rot begins at the flower end of a very young fruit. A squash may start swelling after its female flower opens, then turn yellow, soft and brown within days if too little pollen reached it. This is especially common during cool, wet weather when pollinating insects are less active. Remove the rotting fruit promptly with clean secateurs or by cutting the stalk carefully, so it does not harbour mould or attract slugs. Do not assume the whole plant is diseased because one or two fruits fail. Watch the next female flowers, which have a small swelling behind the bloom, and compare their progress over the following week.
Improve natural pollination by making flowers easy for insects to reach. Grow squash in an open, sunny position, avoid enclosing flowers beneath dense covers during the day and keep nearby flowering plants available for pollinators where space permits. Remove weeds that crowd the base but retain enough surrounding planting to make the area inviting. Avoid spraying flowers with anything that could deter visiting insects. In a greenhouse or polytunnel, open doors and vents on suitable days. Male flowers appear on plain stems; female flowers have a small immature fruit behind them. Both need to be open at the same time, usually in the morning, for successful pollination to occur.
Hand-pollinate when weather is poor or fruit repeatedly aborts. In the morning, pick a freshly open male flower, peel back its petals and gently touch the pollen-bearing centre to the centre of an open female flower. Alternatively, use a small soft brush to transfer pollen between flowers. Work gently and label plants if you are saving seed, as squash varieties can cross-pollinate. Hand-pollination is most useful when flowers are dry and newly open. Do not try to pollinate closed or fading blooms. Repeat on several mornings if necessary, then leave the fruit undisturbed and look for steady enlargement rather than rapid yellowing at the tip.
Keep developing fruits off constantly wet soil. Slide a clean, dry tile, wooden board or a thick pad of straw beneath each fruit once it is established, taking care not to twist the stem. This improves air circulation and reduces the chance of damp patches causing decay. Check supports after rain and replace any material that has become soggy or slimy. Space plants according to the variety so leaves can dry and air can circulate. Water soil at the base in the morning rather than soaking foliage late in the day. A layer of garden compost around, but not against, stems helps retain moisture without leaving fruit directly on bare mud.
Avoid overwatering and cramped container growing. Squash are thirsty when large, but roots sitting permanently in wet compost can become stressed and fruits may fail. Use a large container with clear drainage holes, fresh peat-free multipurpose compost and one plant where space is limited. Check moisture below the surface, then water deeply when needed rather than following a rigid daily schedule. In beds, enrich soil beforehand with well-rotted manure or garden compost and keep a mulch around the root area. Do not pile mulch against stems. Train or gently reposition sprawling stems only while they are young, as older stems can crack and interrupt water flow to fruits.
Distinguish pollination failure from wider disease or pest damage. If fruits are rotting at several stages, stems are soft, leaves are badly mottled or mould is spreading across the plant, remove affected material and improve airflow immediately. Check for slug damage around fruits and use physical barriers where practical. Avoid composting clearly diseased, slimy material if you are unsure it will break down safely; use your local green-waste arrangement instead. The RHS or a local garden centre can help identify persistent symptoms. For next season, give plants more space, start them after the likely last spring frost and choose the warmest sheltered position available.
Frequently asked questions
Why does the end of my squash go brown?
Brown rot at the flower end of a tiny fruit is commonly caused by incomplete pollination. The fruit begins growing, then cannot continue. Remove it, encourage insect access and hand-pollinate newly open flowers on dry mornings if damp or cool weather is preventing regular pollination.
Should I put straw under every squash?
Place a dry support under fruits once they are established and likely to rest on damp soil. Straw, a tile or a small board can work, provided it stays clean and allows air around the fruit. Check it after rain and replace soggy material promptly to avoid trapping moisture.
Can I grow squash in a container?
Yes, if you choose a suitably compact variety and use a large, well-drained container with fresh peat-free compost. Give one plant adequate room, regular water and feeding once fruit develops. Hand-pollination can be particularly helpful on balconies, in greenhouses or where few pollinating insects visit.
General guidance for UK home gardens and allotments. Conditions vary by region, soil and season; the RHS or a local garden centre can give site-specific advice. Page updated 19 Sep 2026.