Bill Fisher, Director of the Crawford County Park District, sent along a photo that really grabbed my eye. It is a snow white Cardinal-flower, Lobelia cardinalis, and as can be seen by its normally colored cohorts, this is atypical. Bill made the photo a day or two ago at their Lowe-Volk Park, where it is growing in the "pollination station".
If you're in the area, stop in and see it. Might be a while before you see another. I can't tell you how many hundreds or thousands of these plants that I've seen over the years, but never a white one that I can recall. Such a form is rare, but occurs with enough regularity to have an official designation: Lobelia cardinalis forma alba. It'll be interesting to see if white ones pop up in this patch in future years.