Are sunflowers weeds?
Not in Kansas. They grow millions of $ worth a year. A "weed" is "a plant out of place". Those Kansas sunflowers growing in Iowa corn rows are considered a weed.
Broadleaf is the type of weed which Pendimethalin controls. Specifically, the herbicide intends to control annual grasses and broadleaf weeds which compete with field corn, cotton, peanuts, potatoes, rice, soybeans, sunflowers, and tobacco. It particularly is effective in controlling broadleaf plantain, Canada thistle, horseweed, lambsquarters, and velvetleaf. It will not be at all effective if the above-mentioned weeds are long-established in their location.