Frost-bitten rhubarb poses an increased risk of unintentional poisoning if eaten in sufficient quantity. The leaves of the plant contain the toxic oxalate compounds (oxalic acid), a component of kidney stones and calcium imbalance.
Symptoms of oxalate poisoning mimic heavymetal poisoning, such as mouth and stomach irritation, generalized weakness, nausea, and vomiting. In severe cases, cardiovascular collapse follows kidney problems, convulsions and coma. Death is rare.
Discard any stalks that have been nipped by frost or frozen since emerging this spring. Soft stalks indicate that the toxic compounds in the leaves have leached back into the edible stalk. Cooking or baking does not make the stalks safe for consumption.
Jo Bjerke is a master gardener. She lives in Virginia, MN.