We've had some rain here lately, and its the kind of rain that thoroughly soaks everything. Now, I've lived near poplars my entire life and I don't ever remember noticing this. Just look at those trunks! They are the brightest shade of green. As they dried, they turned back to their regular white. I pointed this out to my husband, and he had never noticed this either. Now every time it rains, I will be checking to see if the trunks are green.
I did nothing to these photos. They are just straight shots, no special filters or enhancements. Actually, I think the green was a little brighter than this when looking at it, but here you go.