“Clumps of tall grass in my lawn”

Over the past couple of weeks I’ve had a few calls and emails generally about clumps of fast growing grass in lawns. Generally, I see this mystery weed as 1 of following weeds.

  1. Tall Fescue (K31 in a tall fescue yard, or tall fescue in a bluegrass, buffalograss, or Bermudagrass lawn)
  2. Orchardgrass in any lawn, but very common in K31 lawns.
  3. Bromegrass in any lawn, but typically in areas that are near farm land, pasture land, or vacant lots.
  4. Yellow Nutsedge in any lawn, but not during this time of year…typically I’ll get calls about this in June, July, and Aug.

1. Tall fescue.  I was going to show you these pictures and let you guess what they are but here goes.  The first one is clumps of tall fescue in a tall fescue yard that has been ‘fertilized’ by the dog.  It just goes to show you, how underfertilized this lawn is.

The next two pictures below are of K31 in a tall fescue/bluegrass lawn.  The first one was overseeded with K31 at some point in it’s history…the K31 is the light green colored grass.  It has just been mowed, but if I were to come back in a week, the K31 would be much taller than the darker colored turf-type tall fescue.  So K31 has a double negative when it comes to well-maintained fescue lawns, it grows rapidly and needs to be mowed more often, and it is a light green, so most people will fertilize it more frequently to maintain a darker color, which causes it to grow even more rapidly, with even more mowing.

The second picture is a clump of K31 growing in a yard next to the one above.  It had not been mowed yet, so you can more easily see how much taller it is.  You can also see how much wider and thicker the leaves of K31 are compared to turf-type tall fescues.

2. Orchard grass is a cool season perennial like tall fescue.  And it is a bunch-type/clump-forming grass like tall fescue.  It generally has wide blades and a dark color.  The main differences between tall fescue and orchardgrass is that orchardgrass has a very flattened stem with folded vernation whereas tall fescue has rolled vernation.  Moreover, tall fescue has a pointed leaf tip whereas orchard grass has more of a rounded, boat-shaped leaf tip.  And finally, orchardgrass has a very large, membranous, white ligule.  (that means it has a white piece of skin like material where the leaf blade joins the leaf sheath.) It is usually so large and so easy to see, I often use orchard grass ligules when I’m teaching grass ID to people.  Below are 3 pictures of orchardgrass close up.  (sorry if they are a little out of focus….darn camera kept focusing on the ground)

Flattened Folded Stem of Orchard grass. You can even see the white ligule.

Flattened folded stem and leaf. White membranous ligule

White membranous, skin-like ligule sticking out of where the leaf meets the sheath.

Ward Upham recently releases a news article through KSRE about orchard grass.

3. Bromegrass.  Typically, bromegrass spreads by rhizomes, so it may not be a distinct clump, but it is definitely fast growing.   I wasn’t able to find any bromegrass to take a picture of, but the University of Missouri has a good page on bromegrass.  The key charachteristics of bromegrass can be summed up by this photo by Stephen K. Barnhart, Iowa State Press (1997).  The sheath closes back in on itself and forms a v-neck appearance.  And the leaf blades often have a “M-shaped” (or “W” depending on how you are holding the leaf) water mark or branding on them, as seen below.

Smooth bromegrass 'v-neck' sheath and M-shaped watermark on leaf blade. Photo by Stephen K. Barnhart, Iowa State Press (1997).

The downside is there is no real selective control to remove any of these 3 weeds from cool season lawns.  There are products that can remove them from warm season lawns.  But for control in cool season lawns, you can simply dig up the clumps or spot spray the clumps with a non-selective herbicide, like Round-Up.  If the weeds are widespread across the lawn, then the only option is to kill the whole yard and start over.  Kill it and reseed or sod it in September.

4. Yellow Nutsedge.  We will talk more about it later this year, but it is a warm season perennial and it can be selectively controlled in any type of turfgrass with Sedgehammer.

Anybody else seeing these 3 weeds?  Are they giving you headaches?

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  • http://www.ksuturf.com Rodney

    Ahhh, I forgot about Annual Ryegrass. Annual Rye has a lighter green color and grows rapidly. It has a rolled vernation (the new leaves in the stem are rolled) (like tall fescue). It usually has long clasping auricles (those are like fingers that extend the edges of the leaf around the stem). Frequently, it is also purplish near the base. It is an annual so it will die eventually, but it is unsightly until then.
    It used to be common to recommend Annual rye as a ‘nurse’ grass because it will germinate in 3 days to help get the lawn quickly going while the other seeds germinate more slowly. This could be helpful in erosion prone areas. Unfortunately, the annual rye out-competes and out-crowds the desired turf and you end up with a weak thin stand of grass. If erosion or moisture is a concern with seeding, seed blankets, mats, or seed mulch would be much better than straw or annual rye.

    Speaking of straw, I also see wheat as a problem in turf areas that had straw applied to help retain moisture for seed germination. Just like with erosion, if the turf area cannot be irrigated frequently enough to promote good germination, use commercial seed blankets/mats or paper mulch products over straw. The straw usually has too much weed seeds in it. And it either gets applied too heavily which may help hold moisture, but blocks seed germination, or it is applied too light then it doesn’t aid in retaining moisture.

  • http://www.ksuturf.com Rodney

    FYI….Here’s a post from April 2010 on Orchardgrass….http://www.ksuturf.org/blog/2010/04/orchardgrass-tall-and-green/

    (Kinda cool to see similar posts 2 years in a row during April/May….there must be something with spring and Orchardgrass)

  • http://www.sergioslandscaping.net/ lawn maintenance Phoenix

    This is a good source of information about different types grass that are actually weeds on the lawn. The details you have provided can surely help home owners in identifying and finding a solution to get rid of these weeds. Thanks for sharing!

  • Rcohalla

    I  now have a good growth of k31 growing. I have been to not mow it, and then told to keep it mowed. It is dry dry here in Mo. so do not know what to do. Please advise me