We studied only perennials, but annuals and biennials, whichhave a relatively short life-span, may be more vulnerable to herbi-cides and, thus, effects might be visible faster. Annuals and biennialsneed to produce viable seeds in their life cycle. In contrast, peren-nial herbs can persist for many growing seasons because generallyonly the above ground parts of the plants die back each winter andregrow the following spring. However, even perennial species needto reproduce by seeds on occasion to avoid their decline in the plantcommunity. Therefore, it is also important to detect effects of her-bicide applications on reproductive capacity in addition to effectson the plant frequency.