The Tewksbury Historical Society is inviting residents to join its members Sunday for its third annual hike to search for a plant, Scots heather, which played a role in town history. The hike begins at 10:30 a.m. from the Community Gardens on Livingston Street. Steve Ivas, a wetlands biologist, will lead the walk through the Tewksbury Hospital agricultural fields. During the walk, society president David Marcus will give a talk on an episode in the 1860s involving a visitor to Tewksbury who discovered a heath plant growing in the town and submitted it to the Massachusetts Horticultural Society. The society awarded the man a prize for finding a new, native plant, but a debate ensued. Some society members questioned if the plant, which is primarily found in Scotland. was actually native to the Tewksbury area. Many contended it had been planted by a local Scotsman. A national magazine later poked fun at the society over the debate, earning the town and the organization national attention. Today’s talk is free and open to the public.