Dear Gardener (mlefebvre46),

Thank you for reaching out to the UVM Extension Master Gardener Program with your question.

The lack of fruit development in your squash and cucumbers is likely secondary to one of 2 things:

1. Blossom end rot – which is caused by a calcium deficiency. There is usually plenty of calcium in the soil but a variety of factors can effect a plant’s ability to utilize the calcium in the soil: low soil pH, or plant stress (from high nitrogen fertilization, unusually cool or hot temperatures, drought or wet soil). If the calcium deficiency is secondary to low soil pH it will persist throughout the entire growing season. If our unusually warm temperatures and large amount of rain this growing season are resulting in plant stress and calcium deficiency then the condition should improve if our temperatures and rainfall return to normal levels. Blossom end rot can affect other vegetables such as tomatoes, eggplants and peppers. If you are not seeing similar issues on those crops in your garden then perhaps Blossom end rot is not the issue.
2. Poor pollination – both squash and cucumbers have male and female blossoms and require pollination of the female blossoms for fruit production. Bees and other pollinators are less active in rainy weather. Our unusually wet growing season this year may have contributed to decreased pollination of these plants resulting in poor fruit production. You can hand pollinate these plants to improve production.

Selected Resources

Reasons for Poor Fruiting of Vine Crops | Horticulture and Home Pest News (iastate.edu)

Blossom End Rot of Vegetables | Nebraska Extension (unl.edu)

Key to Common Problems of Cucumbers | University of Maryland Extension (umd.edu)

Key to Common Problems of Squash | University of Maryland Extension (umd.edu)

HS1149/HS398: Home Vegetable Garden Techniques: Hand Pollination of Squash and Corn in Small Gardens (ufl.edu)