The present invention is directed to a composition, method, and apparatus for protecting plants from injury caused by frost or freezing temperatures by applying an insulating foam to the surface of plants. Plants are sprayed with a foam formed from a pre-emulsion concentrate comprising a vegetable oil, an emulsifier, and a forming agent. The pre-emulsion concentrate is mixed with water and aerated to form a foam. The foam is then directed onto the surfaces of the plant to be covered.