Rosin Weed is a tall, upright prairie plant that produces branching clusters of large yellow, sunflower-like flowers at the tip of a central stalk. Blooming occurs late summer to early fall and lasts 1 to 2 months. Although it can reach heights of nearly 6 ... feet, it usually stays around 3 to 4 feet tall. Rosin Weed is shorter than the other native Silphium species. Its flowers attract a range of pollinators, and its seeds are a food source for the occasional Goldfinch.