My friend has crocus in her beds and lawn that bloom twice annually, both in the early spring and in the fall. They are a small, pale purple variety. They spread like crazy, having moved out into the whole flowerbed, across wide swaths of lawn, and are even traveling along cracks in the sidewalk. It's a dramatic sight when they bloom. She doesn't know what variety they are and she herself is surprised at their twice-blooming and spreading qualities. Do you know what variety they are?
Perhaps they are Crocus tommasiniansus, a species crocus sometimes simply called tommies, or Crocus speciosus. They multiply rapidly which is both good and bad in my opinion. I don't know for sure but I wonder if some of the fall bloom is from bulblets that reached flowering size that summer.