Zucchini Fruit Rot

Even a healthy young zucchini fruit can start rotting at the stem end. Conway Lum tells us why.

Credit: iStock / GomezDavid

Your healthy zucchini plant produces lots of flowers, but you may notice that its young fruit is starting to rot at the stem end. This fruit will feel soft and may appear water-soaked.

The problem springs from inadequate pollination. When a fruit is not pollinated completely it will begin to rot because the flower is no longer needed for its central purpose of bearing fruit. Flowers on zucchini plants are either male or female. The fruit is produced only on female flowers, which can be identified by the small, swollen fruit just behind the flower. The first few flowers tend to be only male. Flowers are only viable for a few days. To enhance pollination, avoid excessive use of insecticide. Hand-pollinate early in the morning, using a soft brush to transfer pollen from the male to the female flower.

To give your zucchini added help, mulch to ensure even soil moisture when the plants are bearing. You may also need to check the soil’s calcium levels periodically. (If your pH levels are okay, then the calcium is also fine.)

Conway Lum is a horticulturist at Mandeville Garden Centre in Burnaby. Questions can be emailed to him at clumATcanadawideDOTcom.