We call it Lammas or Lunasa, and think of it as marking the commencement of the grain harvest.
And so indeed it does. In Western Minnesota, they're beginning the cutting of the “small grains” even as you read this.
But here in the New World, this was a festival long before the ships from Europe arrived with their sacks of seed wheat and barley.
“Green Corn,” they called it, and among many peoples, it was the greatest feasting of the year.
Maize cultivation came into Northern America from Mexico about 2000 years ago, and spread up along the river valleys. In the Upper Mississippi Valley, where I live, they've kept Green Corn for almost 1000 years now.