Want to keep your summer basil all winter without it turning black? Here is my method. Pull all leaves off at end of summer and wash. Then dump in BOILING water for about 10 seconds. This kills the enzyme that oxidates basil and turns it black. Immediately put in iced water and drain. Then I just put it in a food processor with just olive oil and puree and place in ice cube trays or small containers to use all year as I want.