Yellow Squash Won't Grow to Maturity

by Emily Weller
Yellow squash develops when conditions are right.

Yellow squash develops when conditions are right.

Summer squash (Cucurbita pepo) plants, such as yellow crookneck squash, yellow straight neck and zucchini, typically produce ample amounts of fruit over the course of the season. While squash is known to be prolific, a number of factors can prevent a plant from producing fruit or can damage the fruit before it is ready to pick.

Poor Pollination

Yellow squash plants produce both male and female flowers, but the flowers need some help when it comes to pollination. Usually bees carry the pollen from the male flowers to the female flowers, fertilizing the flower so that the fruit can develop. However, if bees are not common in your garden, the female flowers are likely to fall off the plant before they are pollinated. If you have not seen any bees or other pollinating insects and the flowers are falling off of the plant, you can pollinate them yourself. Dab a small paintbrush into a freshly opened male flower, then dip the paintbrush into a recently opened female flower to transfer the pollen. The male flowers on a squash plant are smaller while the female flowers have a tiny squash fruit at their bases.

Fertilizing Issues

Excess nitrogen in the soil will lead to a lot of leaves and vines on the squash plant, but few fruits. Before you plant the squash in your garden, test the soil. Knowing the soil quality allows you to add the proper amounts of specific nutrients or adjust the pH of the soil as needed. Yellow squash plants prefer soil that has a pH between 6.0 and 6.5. When the plant starts to form vines, it is usually okay to add nitrogen-heavy fertilizer, such as 1 cup of 27-3-3 for every 25 feet of row or 1 pound of 33-0-0 for every 100 feet. But don't add nitrogen-heavy fertilizer once the flowers start to form.

Fruit Rot

Fungal infections can also keep yellow squash from fully developing. Choanephora rot, also called wet rot or blossom-end rot, develops on yellow squash when the weather is very warm and wet. The fungus enters the squash on the blossom end. Within a short amount of time, the fruit is covered in a black and white fuzz. Infected squash fruits should be picked and destroyed. You can protect the squash from the fungus by keeping the fruits off of the soil and by not wetting the leaves or fruits when watering.

Too Many Fruits

The sooner you pick yellow squash from the vine, the better in terms of taste, quality and future fruit production. If you leave squash on the vine to grow too large and over-mature, the plant will have a lower yield as it will stop producing fruits. Yellow squash is ready to harvest when it has a shiny skin and when it is about 1 inch to 1 1/2 inches across. The skin of the fruit should still be soft and a light yellow color.

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