Clearfield Sunflowers give growers an in-season weed control option. CLEARFIELD SUNFLOWERS ARE NOT GLYPHOSATE TOLERANT! Instead, they are able to be sprayed with Beyond® Herbicide, which is available online or at many ag retailers. 
What do they do: Beyond® offers the option of controlling broadleaf weeds even once the sunflowers have emerged. This helps to allow the ground to stay free of weeds, giving gamebirds the best access possible to seeds.
Site Prep & Planting: Sunflowers do best when they are planted 1" - 1.5" deep in 20" or 30" rows. Do not plant until soil temperatures have reached a daily minimum of 50° F. ALWAYS READ & FOLLOW HERBICIDE LABEL INSTRUCTIONS!
Maintenance: Will winter kill. Typically need a fertilizer offering nitrogen and potassium.