Hannibal has earned the Tree City USA for 25 years and Hannibal Parks & Recreation is celebrating with a “Searching for Mother Trees” nature program at Riverview Park. The program is free and open to the public, it begins at the shelter by the playground at 1 p.m. Sept. 15 and will be led by nature educator Gale Rublee. Reservations for nature programs may be made on www.hannibalparks.org