On Saturday, July 8, from 10 a.m. to noon, the Friends of the Oxbow National Wildlife Refuge will host a morning of nature sketching. Participants will walk the trails and identify and sketch plants. The instructor, naturalist Ron Balco, has trained in the art of botanical illustration. Meet at the Bill Ashe Pavillion, 80 Hospital Road, Devens. For more information call 978-770-2259.