Mackinac Island's lilac bushes — planted by 19th-century settlers from seeds brought from France — now number in the hundreds and cover much of the island. Every June, when they bloom simultaneously, the scent carries all the way to the ferry dock. The ten-day Lilac Festival has been running since 1949 and includes a horse-drawn carriage parade down Main Street, a ten-kilometre road race, and various events centred on the blooming season.
The festival's dates vary by year depending on when the lilacs actually flower, which can shift with the weather. It typically falls in the second and third weeks of June. Even outside festival week, the blooming season (generally mid-May through mid-June) is one of the most pleasant times to visit the island — the tourist crowds haven't peaked yet, the weather is warming, and the entire island smells remarkable.