How Does Pre-emergent Crabgrass Control Work?

Category: Lawn Care

crabgrassCrabgrass is one of the most known weedy invaders in your lawn. Even if you can’t tell the difference between it or any other grass, you’ve probably heard of it. Crabgrass is an annual summer grassy weed that invades lawns, choking out the desired turf grass species. What makes matters worse is that when the first hard frost of fall arrives, this warm-season plant dies off, leaving a big, brown ugly mass of dead weedy growth containing no turfgrass left to fill in. Guess what will be there again next year? You got it, more crabgrass.

A single crabgrass plant can produce approximately 75,000 seeds in one growing season. These seeds, fall to the soil to continue the cycle in the following year, unless something is done to remedy the situation. Crabgrass pre-emergent (or preventer) herbicide is one of the first control materials applied to lawns in the spring. The concept behind a pre-emergent is that you control the weeds before they emerge. These herbicides come in a wide arrange of formulations and active ingredients. Each has its own benefits, and all are not created equal. Each material has different time frames it can be applied, so consult the instructions on the material’s label for best recommendations.

How granular crabgrass pre-emergent worksThe majority of crabgrass pre-emergent applications are applied in a granular form. This form is easiest to calibrate equipment to deliver the recommended dosage. Hand-spraying applications of this material in a liquid form can drastically fluctuate in delivering the proper amount to the lawn areas. As this material is applied, granules disperse in the lawn. As these granules come in contact with water from irrigation or precipitation, they dissolve and are evenly distributed into the top inch of topsoil below the grass plants.

lawn fertilizer spreaderAs soil temperatures warm consistently and moisture is present, the millions of crabgrass seeds in your soil have their opportunity to start growing. If nothing is impeding their development, you’ll soon have a big crop of crabgrass emerging. Pre-emergent crabgrass control creates a layer of this material waiting to stop this. As the germinating seed comes in contact with the material, it stops developing. This works in the majority of areas that have average to dense turfgrass.

If areas of lawn are very thin or bare, pre-emergent crabgrass control won’t be effective. Sun baking the soil, soil cracking in lack of moisture, and leaching in the soil will disrupt the layer of protection that was applied. Likewise, aggressive trimming of edges of lawns and mowing at heights below 3″ will leave areas where the material layer has been removed or disrupted. Maintaining a thick lawn is essential to reducing crabgrass germination.

Often, there are areas that will have break-through and crabgrass will emerge in early summer. This is why it is important to enlist a lawn care company that provides a lawn maintenance program with post-emergent crabgrass control to spot-spray these areas before they can get out of control.

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