Volunteers are needed to help find and pull water chestnuts, an invasive exotic weed, from local stretches of the Nashua River from 9 a.m. to noon on June 29. Gathering baskets and maps will be provided. Nashoba Paddler in West Groton will provide a limited number of canoes, and volunteers can also bring their own boats. For more information, contact Martha at email@example.com or 978-448-0299. To reserve a canoe, contact Nashoba Paddler at 978-448-8699.