Will Bagging Clippings Get Rid of Johnsongrass?

Know Your Enemy

• Johnsongrass is an aggressive, sod-forming weed that tolerates infertile soil and harsh environmental conditions. Perhaps the most intimidating characteristic of johnsongrass is its ability to invade new areas and subsequently spread in dense patches that choke out desirable vegetation. Johnsongrass spreads by vigorous underground stems known as rhizomes, but it also establishes readily from seed, and one johnsongrass plant can produce thousands of seeds. Consequently, early mowing and removal of seed heads are essential aspects of johnsongrass control.

Do Not Sow the Seeds

• Any time you mow your lawn with johnsongrass seed heads present, you help the plant disperse its seeds. If your lawnmower is configured to mulch grass clippings, then it deposits the seeds onto the soil surface, where they will germinate and begin a new generation of pestiferous weeds. A side-discharge lawnmower is slightly better for johnsongrass control because it throws some of the seeds beyond the lawn's boundaries. The seeds, however, will threaten other areas of your home's landscape. By far the best option is to bag grass clippings so that you can distribute the collected seeds in a secure location.

Compost If You Dare

• The safest way to dispose of grass clippings containing johnsongrass seeds is to burn them or treat them like ordinary trash or green waste. Doing so, however, results in a serious loss of nutrients and organic matter that many homeowners, especially gardeners, prefer to avoid. An alternative is to compost the clippings, but carefully manage your compost pile to ensure weed seeds are destroyed. Three days of temperatures above 120 degrees Fahrenheit is sufficient to kill johnsongrass seeds, but the compost pile needs to be turned several times to ensure all of the compost materials are exposed to those temperatures.

Bolster the Good Grass

• A fundamental, yet often overlooked, approach to weed control is simply doing everything possible to encourage desirable grass species. That approach is particularly important when dealing with johnsongrass in a lawn because herbicides are impractical when trying to eliminate a perennial grass species that has infested a lawn full of other perennial grass species. Adopt the mowing, irrigating and fertilizing practices preferred by the desirable species in your lawn, especially practices -- such as frequent close mowing -- that are injurious to johnsongrass.