This post took longer than most to finish because I was determined to find out what these mystery plants were. I first found them two weeks ago, growing about 15 feet apart, with similar leaves. Only one had the beginnings of flower buds. A few days later I went back to see them and found that the taller one's buds were red! Wow. I had no idea what this could be. The smaller one had young (still green) buds, but I assumed they would be the same. Back again and the smaller one's flower was yellow. Yellow? Yes, definitely yellow. By this time I could tell that the flowers were compound umbles, which would make identification possible. After drawing the plants and the beautiful ground beetle that scurried past where I sat, I headed home to my field guides.
They weren't easy to find. After some false starts, and thinking for a while the yellow one was possibly a Golden Alexander, then a Heart-leaved Alexander (but what was the red one?). I ruled those out when I found an entry online showing a photo of Meadow Parsnip (Thaspium trifoliatum) in yellow and an inset photo of the alternate color, purple. Purple? But the photo showed the same reddish flower as my plant - not what I call purple! Very satisfying.