CHARLESTON, W.Va. -- Folk singer Peter Yarrow has canceled his May 11 performance for the Woody Hawley Series. According to the Clay Center, Yarrow has a scheduling conflict.The 74-year-old singer-songwriter and political activist is best known as one of the members of Peter, Paul and Mary, a successful folk trio in the 1960s that charted numerous hits. Several broke into the top 10 on the pop charts, including "If I Had a Hammer," "Blowin' in the Wind" and "Leaving on a Jet Plane." Yarrow also co-wrote Peter, Paul and Mary's iconic hit "Puff, the Magic Dragon."Yarrow's cancellation may bring the Woody Hawley Series to an early close this season. Kelli Markovits, marketing coordinator for the Clay Center, said, "We are not rescheduling another act at this time."Ticket holders for the event are being notified by the Clay Center, with instructions on how to obtain a refund. For information, call 304-561-3570 or visit www.theclaycenter.org.