When I stopped at Amnicola Marsh a few days ago to check on the status of the American Lotus (they were blooming), I noticed a bright yellow blossom on a prostrate red stem in the cracked mud bottom (we are in a drought, and the water level is very low at the Marsh.) Cindy asked what it was, and I told her I thought it was a primrose-willow (Ludwigia species.)
I chose to use the Creeping Water Primrose common name for Ludwigia peploides rather than another one commonly used – Floating Primrose Willow – because the drought we’re in had this plant many yards away from being floating.
I took a couple of quick photos, thinking it was the Ludwigia that I had photographed within feet of this spot a few years earlier. But when I got home and looked at the photo I had taken and those of the other two Ludwigia that I had identified in previous years, I noticed that the flower in my new photo had 5 petals while the other two Ludwigia had 4 petals. I had other things to do, so it was several days before I was able to return to this mystery. Some research was in order, so I hit Google with a search for “ludwigia 5 petals” (my copy of Wildflowers of Tennessee, the Ohio Valley and the Southern Appalachians: 2nd Edition