One example is the Preen Weed Preventer Plus Plant Food ... While Preen is a well-respected brand and has one of the best crabgrass killer products on the market, in any situation where you ...

One reviewer noted that Preen isn't a crabgrass killer but a preventer. The implication is that this product, even as a sometimes post-emergent treatment, isn't meant to deal with a lawn full of ...