Hail may completely destroy young cabbage that has yet to form a head by shredding the leaves. The leaves gather and store food for the developing core of the plant, and without them, development is arrested. When this happens, the cabbage plant is unable to recover and dies. Older cabbage may be salvaged after a hailstorm by harvesting it and tearing away the damaged leaves. The unharmed core may then be used or sold. If the cabbage is only lightly damaged and the majority of leaves remain in tact, the cabbage plant has a good chance of survival and normal harvest, though the outside of the head may be scarred.
Not much can be done to save large cabbage crops in the event of sudden hail storms. If growing a few heads in your backyard garden, you may be able to protect them from forecast hail by temporarily providing them with cover. Upside down bowls or buckets may serve, or stakes driven along a row and draped with a tarp. Be sure to weight or tie down any coverings as hail is usually accompanied by winds.
Cabbage heads consist of many layers of leaves folded over one another. When hail damage occurs, it is often possible to pull off the affected leaves, revealing an untouched core. Cabbage may also be consumed at any stage of its growth, and damaged heads may be harvested and eaten right away before bruising and rot sets in. While cabbage attacked by hail is not very nice to look at, the taste is unaffected if used immediately.
In the event of a severely damaged crop, harvest all the heads by cutting through the stem with a sharp knife immediately below the head, leaving the stem and roots in tact. The stem will produce off-shoots, or sprouts of small cabbages that can be grown, harvested and used similar to Brussels sprouts.