The Weed Science Society of America has designated perennial pepperweed as the official common name for Lepidium latifolium L. In the San Luis Valley of Colorado, nearly everyone refers to the plant as ironweed. Throughout much of the western United States the plant is known as tall whitetop. Unfortunately, another weed commonly called “whitetop” is widely distributed on rangelands. The scientific name of this whitetop is Cardaria draba [L.] Desv. and the accepted common name is hoary cress. This may seem confusing, but it results in a communication rather than an identification problem. If correspondence arrives reporting a “whitetop” problem at a field location, it is necessary to determine the exact species that is being referred to as the problem. In the field, it is generally easy to distinguish between Lepidium latifolium and Cardaria draba.