Ben McCanna/Staff Photographer Something is always happening around Boothbay Harbor, what with a lively restaurant and bar scene, family attractions and scenic wonders. But this there’s even a bigger reason than usually to visit the area – giant in fact. An exhibit of giant wooden trolls built among the trees at Coastal Maine Botanical Gardens in Boothbay called “Guardians of the Seeds” will open to the public Saturday. It features five wooden trolls built by artist Thomas Dambo, from Denmark, and scattered around the gardens’ 323 acres. Some are in plain sight while others are deeper in the woods. They range from 15 to 30 feet high. Their mission is to protect the seeds of the forest and teach people about sustainability.