Why Are My Baby Watermelons Shrivelling and Falling Off?

The female flower opens, a tiny round fruitlet the size of a marble forms behind it, and then — within a few days — the fruitlet turns yellow, shrivels and falls off, taking your hopes for the season with it. This is one of the most common and discouraging problems in watermelon growing, and it happens because the fruitlet was not successfully pollinated. Without fertilisation, the plant has no reason to invest energy in developing the fruit and it is abscised naturally.

Distinguishing pollinated from unpollinated fruitlets

A successfully pollinated fruitlet begins to grow steadily within three to five days of the flower opening — it firms up, becomes rounder and larger each day, and the flower petals drop cleanly. An unpollinated fruitlet stays small, begins to yellow at the tip and softens within four to seven days before dropping. If fruitlets are consistently yellowing within a few days, pollination is not occurring.

Causes of poor pollination

Watermelon relies on bees to transfer pollen from male to female flowers. In gardens with few pollinators, during rainy periods when bees are not flying, in early morning when bees are not yet active, or when plants are covered with row cover that excludes insects, insufficient pollination occurs. Also: male and female flowers must be open at the same time — if only male flowers are present during a bee visit, no pollination happens that visit.

Hand-pollinate to guarantee fruit set

Find a fully open male flower in the morning when pollen is being shed — male flowers have a straight stem with no swelling at the base, and the central stamen is covered in yellow pollen. Peel back the petals to expose the stamen fully. Find a female flower (with the small round swelling at the base) that is also fully open. Gently rub the pollen-covered stamen against the sticky stigma at the centre of the female flower. One male flower provides enough pollen for three to four female flowers. Repeat on consecutive mornings while both types of flowers are open.

Temperature extremes during pollination

Pollen viability drops in very high temperatures (above 35°C) and very low temperatures (below 15°C). In cool early mornings or heat waves, even if bees are active and both flower types are open, pollen may not be viable. Hand-pollinate during the warmest part of the morning, before noon, when temperatures are in the comfortable 20–30°C range.