Mar 10, 2022
Protect strawberry flowers and fruit from frost injury

Recent frosts at the Cal Poly farm in San Luis Obispo, California, has brought frost injury in all its variety. According to the Compendium of Strawberry Diseases “frost injury is probably the most common non-pathogen related and non-insect-related disorder affecting strawberry flowers and fruit.”

Whenever temperatures dip to below freezing, expect to see a variety of deformed fruit and blackened flowers. The extent of the injury varies with the stage of flower development, temperature and duration. The entire flower may be lost or only a few pistils, in which case the result is malformed fruit. In later stages of fruit development, you may see a woody portion of the fruit where achenes are tightly spaced. In mature fruit the pith may be corky and slightly brownish.

Cultivars vary in their sensitivity to frost, but I’m unaware of any systemic rating of this injury in the published literature. Frost damage can be minimized by overhead irrigation during low temperatures or by growing beneath plastic tunnels. Wind machines have been used when thermal inversions keep higher temperature air trapped above ground-level air.

Below is a photo gallery of some of the injury I saw on 8 Mar 2022, about a week after we experienced a few nights in the low 30s. Note the fruit deformation, hardened/woody areas, uneven ripening and blackened flowers. Following frost, expect some rough fruit shapes to show up for the next few weeks. Fortunately, the plants will survive and produce more flowers, hopefully under better conditions for fruit development.