Preen Garden Weed Preventer Plus Plant Food works all season long. 1 application prevents weeds up to 3 months and feeds your plants for beautiful color, foliage, and strong roots to help avoid insects and disease. This product can be used anytime during the spring, summer, or fall in flower and ornamental garden beds, around ground covers, trees, and shrubs. Although this product will not kill existing weeds, it will prevent new weeds from sprouting, eliminating the need for difficult and time-consuming hand weeding. There is no chance of overfeeding or burning your plants when used as directed.