Classic Lawns

Cary’s Corner – Johnsongrass

Cary’s Corner – Johnsongrass

At Classic Lawns we have a motto of Growing Grass and Smoking Weeds!  While this motto is a fun, tongue in cheek slogan for what we do, there are some weeds that we have trouble “smoking.” While the list of weeds that Classic Lawns cannot control (without harming your good grass) is relatively small, there are some weeds that frustrate even us.  One of these weeds that seem to be very prominent this year (partly due to an extremely mild Winter) is Johnsongrass.

Johnsongrass
Johnsongrass next to a quarter!

What is Johnsongrass?

Here are some facts about Johnsongrass:

  • Johnsongrass is a perennial grass which means it can live from year to year.
  • It is a very wide bladed grass that grows quickly. If left unmowed it can grow up to 8 feet tall.
  • Johnson grass spreads by seed and rhizomes. Rhizomes are horizontal underground plant stems capable of producing the shoot and root systems of a new plant.
  • Johnsongrass rhizomes are extensive and produced in top 10” of lawn but have been found at depths of 5 feet!
  • Johnsongrass readily reproduces from rhizomes and seed; seedling plants can initiate rhizomes as few as 19 days following emergence.
  • A single plant may produce more than 80,000 seeds in a single growing season, and 275 feet of rhizomes.
  • Seeds shatter 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 10 years.

Why is Johnsongrass so hard to control?

We share all this info with you to help explain why it is so hard to prevent, control and kill Johnsongrass.  Here are some of the reasons controlling Johnsongrass is extremely difficult.

  • As part of our lawn program Classic Lawns applies pre-emergents to help prevent grassy weeds from even germinating. While these pre-emergents do a good job of helping to prevent crabgrass and foxtail, they rarely prevent Johnsongrass because Johnsongrass seeds are so large compared to crabgrass and foxtail seeds.  Plus, the fact that Johnsongrass can reproduce from Rhizomes in the soil from year to year makes pre-emergents non effective on them.
  • Once Johnsongrass is up, it is VERY difficult to kill. Well, we can kill it with RoundUp, but that would also kill your good grass!  The problem with killing Johnson grass is equivalent to trying to invent a poison that you and your cousin could both take, but the poison would only kill your cousin.  Johnsongrass is just too closely related to fescue and bluegrass.
  • We have heard so many customers say, “We have never had this much Johnsongrass before. Why do we have it so bad now?”  One reason is the mild winter we had in 2015-16.  We didn’t have enough cold weather over the last several years to knock out the plants seeds and rhizome system.  Another reason is all the rain and wet weather the last few years have made it so dormant seeds can easily now germinate.
  • Probably the biggest reason for more Johnsongrass is that up until 2009 the lawn care industry had a product that we could use called MSMA that did a decent job of knocking out Johnsongrass without harming your good grass. Even though MSMA is no more harmful to people than many products we still use today, the EPA changed regulations for testing products in the early 2000’s which made it too expensive for companies to produce MSMA.  As a result, the company that made MSMA just quit making it instead of going through the expensive of passing the EPA tests.   So, the best weapon we had no longer is available.

So what do we do to get rid of Johnsongrass?

Johnsongrass in a lawn.
Johnsongrass in a lawn.

The lawn care industry does have some newer products that are showing some promise in controlling Johnsongrass.  So far, nothing works as well as MSMA did.  As an industry, we are going through a trial and error period of finding out what products work, when to apply them, what to mix them with and what will not hurt our good grasses.  Catching Johnsongrass early before it spreads and hitting it with a product we have available works ok.  The results are hit and miss.  There are some products that work better in the fall that we can apply in late September or October.  Still they are not perfect.  We can do a pretty good job of killing it out with RoundUp, but you then have to seed where we have killed off your good grass too Even farmers are having a tough time with Johnsongrass.  Learn more here: http://extension.missouri.edu/p/g4872

If you do not have a lot of Johnsongrass, we highly recommend spending a little bit of time pulling it out by hand.  We understand that this is not the answer you want to hear when you hire a lawn care company like Classic Lawns, but unfortunately it is the best way to get rid of it.  Try to pull it when the ground is wet and soft so you can get as much of the roots and rhizomes as possible.   Keep an eye out for any new sprouts and pull them before they spread or go to seed.  We try to help you out with this chore when we are on your lawn applying one of our applications.  If there is not too much, we pull it while we are there.  If you have a lot of Johnsongrass, we may also try to control it with one of our newer products that we are testing.

At Classic Lawns we are doing what we can to knock out Johnsongrass for our customers, unfortunately so far, we just do not have a great solution for the problem.  We will keep doing our best!

 

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