Foliar Feeding of Calcium Chloride and Watermelon

Watermelons (Citrullus lanatus) take so long to develop that losing any of the fruit to blossom-end rot is a big disappointment. Blossom-end rot is a dark, sunken, squishy spot on the end of the melon opposite the stem, and is caused by a calcium deficiency or disruption. Nothing can restore the fruit once blossom-end rot sets in, but foliar calcium chloride treatments are one method of preventing the disease.

Calcium Chloride

A recommended preventive measure is a solution of 2 tablespoons of calcium chloride in 1 gallon of water sprayed on the foliage and fruit of watermelons at least twice during the growing season at one-week intervals beginning when the flowers start blooming. Premixed solutions are also sold. Calcium chloride is a source of calcium as well as salt.


Calcium chloride is not universally recommended as a treatment for blossom-end rot. Because it is also a salt, it can burn foliage when over applied. Foliar application is also considered less effective than if the solution is used as a soil drench because calcium does not move well from leaves to fruit and is taken up better by the roots. Keeping moisture in the garden consistent, planting only in areas with good drainage and avoiding damaging roots with too-deep cultivation allows for the best uptake of available soil calcium.