Unidentified yellow wildflower

I would like to identify this yellow wildflower, which is growing in several low-lying (and generally moist) spots on my property, mostly in substantial shade, even under black walnut trees. The flower and foliage photos were taken on 27 September, and the seeds were collected in October. The plants are as tall as perhaps 4 ft. The largest leaves are maybe 7 in. across on a plant that size, but many are smaller. The stems have a hexagonal cross section and have a narrow hole running down the length. The crushed leaves have no particular odor. I believe the plant must be a perennial, as there are very small and very large plants in the same area. Any help you can provide would be much appreciated.