Available for pickup only, Walmart offers the Preen Garden Weed Preventer Plus Plant Food 5.6-lb. Jug for $11.91. (Target and Amazon offer it for the same price.) That's the lowest price we could find by $7. It feeds plants and prevents weeds for up to three months.

Note: Target offers the Preen Garden Weed Preventer 5.6-lb. Jug for $10.87. (Amazon offers it for the same price.) Opt for in-store pickup to avoid the $4 shipping charge. That's the lowest price we could find by about a buck.