We expect frost until the last third of May and direct frost always kills new growth that slows down the growth process as Pino just mentioned. However placing some fabric (cotton) sheet on top of the plant overnight and removing it in the morning can save the new growth. The direct frost on leaves is the killer. Placing plastic sheet directly on the plant and not removing in time before the sun heat can also burn the new leaves. To cover many plants, when frost is expected, I use a tarp that is kept high not touching the plants