We have Nimblewill In Our Lawn - August 2022

I had a little lawn care breakthrough this past week.  Turns out....I don't have Poa in our lawn.  We have a bent grass called Nimblewill.  Since last Fall, I've talked about how I needed a plan to deal with what I thought was Poa Annua in our backyard.  I sketched out the notion of a full back renovation and even included the idea in my 2022 to-do list.  

But, as I was thinking about the timing of killing that (presumed Poa), I started to dig a little deeper on the Web.  I pulled a blade of my invasive grass and compared it to what I found on the Web.  It wasn't looking like Poa.  Then...I found this page from Purdue's Turf Science Department that talks about Nimblewill.  

Purdue describes Nimblewill thusly:

Nimblewill (Muhlenbergia schreberi) is a warm-season perennial grass found throughout the northeast, southeast, and Midwestern United States.  
...It grows well in moist, shady areas but it is also found in dry, sunny areas. Nimblewill spreads vegetatively through short, weak stolons and creates patches in lawns that start off small, but then grow into larger patches.

Here's the blade of grass that I pulled from our lawn below:

It sure looks just like what I'm seeing on the Purdue site.  Then...if you scroll down, you'll see photos that show dormant Nimble well.  Huzzah!  

Now that I know what it is, what do we do about it?  Turns out, there is the traditional cultural control approach:  have a healthy, full lawn that will crowd it out.

Unfortunately, I'm well past that.  This stuff is everywhere.  Here are a few photos below that show Nimblewill taking over our yard in spots:

Purdue's Turf Science program details that there are a couple of herbicide controls that would work - the first being Roundup.  Just kill everything.  Including the other grass.  The other is something called Tenacity.  

Mesotrione (Tenacity) can be used for selective control of nimblewill growing in a cool-season turf. To control nimblewill, start applying mesotrione in the spring (late-April) with a nonionic surfactant at 0.25% (v/v). You will need to make two or three applications. ...You can also apply mesotrione in late summer and fall, but you should initiate them by August for best results.
Emphasis, mine.

Iowa State Horticulture Extension says much the same:  A couple of applications of Tenacity will turn Nimblewill white, stop it from growing and eventually kill it.  

That means...I could begin to kill this stuff now - while it is growing.  Then...follow with a second killing to make sure I 'get it all'.  

One of the features of Tenacity (that I'm learning about) is that it can live with seeding at the same time.  Meaning...I can spray this Nimblewill now (August) and then throw down my seed (overseeding) a couple of weeks later.

Off I go to try to find Tenacity.  Which...it appears to require a surfactant when applying as a post-emergent.  And...then seed at least 60 days before our first frost.  Combo of Tall Fescue and Kentucky Blue Grass across the back?  

KBG doesn't do well in shade, so I'm planning on overseeding with Tall Fescue in the far back.  I have KBG up near the house, so I'll overseed (again) with Tall Fescue there, too.  In the middle part of the lawn, I have a thin, wispy perennial rye grass that flops over.  I'll lay down a combo of KBG and Tall Fescue there to try to diversify the turf in that section.

3 bags of Tall Fescue for entire lawn
2 bags of KBG for front and middle

Leaving us with a combo lawn of Tall Fescure, Kentucky Blue Grass and some (likely) fine fescue or Perennial Rye Grass.

What about adding a compost layer to the very dry part of our swale that always goes dormant?  Or some lawn soil in parts.  Seems like a no-brainer.  I'll do a post on the timing of this process in the coming days.


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