The Collaborative International Dictionary
Helenium autumnale
Sneezeweed \Sneeze"weed`\, n. (Bot.) A yellow-flowered composite plant ( Helenium autumnale) the odor of which is said to cause sneezing.
Wikipedia
Helenium autumnale
Helenium autumnale is a North American species of flowering plants in the sunflower family. Common names include common sneezeweed and large-flowered sneezeweed.