Preen Garden Weed Preventer stops weeds from germinating in flower and vegetable gardens, in ground covers, and around trees and shrubs. Preen will not kill existing weeds. It will prevent new weeds from sprouting — eliminating the need for difficult and time‑consuming hand‑weeding. Without weeds, your valuable plants can grow larger and stronger. With Preen Garden Weed Preventer, you can stop weeds from growing in your landscape for up to 3 months. 16 lbs. covers 2,560 sq. ft.