AgEBB-MU CAFNR Extension

David Burton
Civic Communications Specialist
2400 S. Scenic Ave.
Springfield, MO 65807
417-881-8909
417-881-8058
burtond@missouri.edu

July 21, 2017


Johnsongrass in Lawn is
a Formidable Foe for Homeowners


SPRINGFIELD, Mo. - The bottom line is that eliminating Johnsongrass from a home lawn is not easy. But that hasn't stopped the phones from ringing at the Master Gardeners of Greene County hotline at the Greene County Extension in Springfield.

"The good news is that fall is a great time for applying glyphosate," said Patrick Byers, horticulture specialist with University of Missouri Extension.

MENACING WEED

Johnsongrass can produce seed and rhizomes and spread to uninfested areas which make it a menacing weed.

Rhizomes are extensive and are produced in the top 10 inches of soil but have been found at depths of five feet according to Tim Schnakenberg, agronomy specialist with University of Missouri Extension.

"Johnsongrass readily reproduces from rhizomes and seed. In fact, plants can initiate rhizomes as few as 19 days following emergence," said Schnakenberg.

A single plant may produce more than 80,000 seeds in a single growing season, and 275 feet of rhizomes. Seeds scatter easily and fall to the ground beneath plants that produce them.

Instead of germinating uniformly, seeds can remain dormant and produce plants over several years. Johnsongrass seed can remain viable in the soil for more than ten years.

RECOMMENDATION

For home lawns, the typical recommendation for responding to johnsongrass has three steps according to Byers.

First, general applications of glyphosate (found in Roundup and other projects) kills Johnsongrass and all other green vegetation over large areas.

Second, spot applications of glyphosate can be used to kill Johnsongrass in vegetable gardens, flower beds, ditch banks, and fence rows.

Third, reapply when johnsongrass greens up again and then repeat. By weakening the plant this time of year, you increase the odds of it dying out in cold winter weather.

Other herbicides can be used in pasture and crop situations. One of the new products for responding to johnsongrass in fields, Outrider, is not registered for lawns.

"Outrider's active ingredient is sulfosulfuron, and I have not found a turfgrass product with this chemical in it. There are some close cousins like Manage, Manor, and Corsair," said Schnakenberg.

MORE INFORMATION

The Missouri Department of Conservation has a good control guide for Johnsongrass at http://mdc.mo.gov/your-property/problem-plants-and-animals/invasive-plants/johnson-grass-control.

University of Missouri Extension also has a guide sheet, G4872 "Johnsongrass Control" that is available online at http://muextension.missouri.edu.

For more information, contact one of MU Extension's horticulture specialists or educators in southwest Missouri: Patrick Byers in Webster County at (417) 859-2044, Kelly McGowan in Greene County at (417) 881-8909 or Robert Balek in Jasper County at (417) 358-2158. Or, call the gardening hotline operated by the Master Gardeners of Greene County at 417-874-2963.


Source: Patrick Byers,(417) 859-2044

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