Why Doesn’t Weed and Feed Kill All of My Broadleaf Weeds?

“I put weed and feed (broadleaf weed killer) down, but the plantago weed is still there. Why?” Question from Sandra of Cottage Grove, Minnesota

Answer: There could be several possible reasons. Before covering them, let me give an overview of how most weed and feed lawn herbicides work. Broadleaf weed killers that also feed grasses only kill broadleaf weeds, like dandelions, plantago, and clover, not grasses. Non-organic weed and feed products typically contain the chemicals (2,4-D) and mecoprop-p, for weed control.  2,4-D and mecoprop-p are most active at killing weeds after they have sprouted (annual weeds are easier to destroy). Here are several reasons why your perennial plantago may still be surviving.

1. You did not apply at the right time. Broadleaf weed killers must be used when plants have sprouted and are actively growing. If applied too early in the spring, they are not as effective.

2. Weeds seeds are a problem. These chemicals are not as impactful on weed seeds, so it is important to apply them after weed seeds have sprouted. (Very early in the season, try using corn gluten, an all-natural pre-emergent that stops weed seeds from germinating.)

3. Encourage thick grass and thatch. Thick grass discourages weed seeds from sprouting. Mow grass higher to encourage a lush lawn, and don’t rake away the thick layer of thatch (the carpet of dead grass below the living grass) because this also keeps weed seeds at bay. There are always loads of seeds below the thatch just waiting to sprout.

4. Perennial weeds are tougher. Plantago is a perennial weed, and these are a lot tougher for herbicides to kill. Be sure to follow application guidelines and warnings for full effect. Most guidelines suggest the product be applied again in the fall.

Chemicals in traditional weed and feed products are pretty harsh. If you are interested in a comparable organic option, there are several all-natural broadleaf weedkillers on the market.

In the meantime, pulling up really large, annoying plantagos is an option. Getting the worst specimens out of the way will likely make you feel better until the next application.

I hope that this information helps!

Jessie Keith

Black Gold Horticulturist