The USDA may not have been the first to decide this is a weed. 4000 years ago, native Americans grew this, and ate the nutritious seeds. But by the time of the European invasion, it was no longer grown, replaced by corn, sunflowers and pumpkins. Marsh elder has also been called sumpweed, probably because of its um, er, . . . aroma. On top of that, it likely makes you sneeze. Altogether, it's no one's favorite plant.