Comedian Preacher Lawson will bring his hilarious act to the Open Air Theatre at Longwood Gardens on June 20, beginning at 7 p.m. in a performance presented in partnership with Voices Underground as part of their Chester County-wide commemoration of Juneteenth. Best known for his appearance on season 12 of “America’s Got Talent,” Lawson has also performed on “America’s Got Talent: The Champions” and “Britain’s Got Talent: The Champions.” For tickets, visit www.longwoodgardens.org/events-performances/events.