Early June is the best time to see them flowered. We were there on June 7 and some had already gone by
I did not see any this July.
I was just walking through the area and saw several clumps of them on the Maine woods trails. They were just starting to grow the bud of the flower. I heard from others that day that a few were in bloom but I never saw any personally. I'd say May 28th-31st would be safe dates to see them starting to be in bloom.
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