This refers to the leafy greens which are attached to raw beets when you buy them. Many people cut them off and throw them away but that's a bad choice, because it turns out the greens on top have more antioxidants than the actual beets do themselves!
ORAC Source
USDA Database for the Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods, Release 2 - Prepared by Nutrient Data Laboratory, Beltsville Human Nutrition Research Center (BHNRC), Agricultural Research Service (ARS), U.S. Department of Agriculture (USDA) - May 2010