CO-Horts

CO-Horts

Tuesday, July 22, 2014

Weed of the Moment: Crabgrass and its look-alikes

By: Tony Koski, Turfgrass Specialist

Guess what? You might actually be seeing crabgrass in your lawn this time of year! It was late germinating this spring (we didn't see it in Fort Collins until late May), but now it's large and in charge. This is crabgrass in late May:
Young crabgrass
Now it looks like this (late July):
Small (smooth) crabgrass (Digitaria ischaemum)
Small (smooth) crabgrass--growing in concrete!
(That's a joke)
Small (smooth) crabgrass near sidewalk
Crabgrass seedhead
Many think they have crabgrass, but they don't. Here are some other crabgrass look-alikes that are often called crabgrass, but misidentified...

This is not crabgrass; this is bromegrass (wide, coarse blade; often a "W" watermark on upper tip of leaf):

Bromegrass in a bluegrass lawn
This is not crabgrass; this is annual bluegrass (characteristic apple green color; often with seedheads):
Annual bluegrass in a Kentucky bluegrass lawn
And this is not crabgrass; this is tall fescue (clumps of grass with rough edges on the leaf blade):
Tall fescue in a bluegrass lawn
 This isn't crabgrass either; this is orchardgrass (flat "stems" and tall white ligule):

The ligule is located like a collar on the inside of the leaf

Orchardgrass in the lawn
And no, this isn't crabgrass either; this is yellow foxtail (characteristic red base, yellow-y color):
Yellow foxtail, which can easily be confused with crabgrass.
The great news is that the same products that work on crabgrass
will work on foxtail.
Yellow foxtail--look at that distinctive red color!
Finally, this isn't crabgrass--this is bermudagrass (forms runners, invasive, pointy leaf tip):
Bermudagrass
Crabgrass is characterized by its prostrate growth habit, especially after mowing and a light, apple green leaf color. The seedheads are digitate (finger-like) and will begin forming in earnest in August. Crabgrass is a warm season grass (and a summer annual), so it will die with the first frost.

If you want to control it now, use any herbicide product containing quinclorac (such as Ortho Weed Be Gon Max Plus Crabgrass Control, Fertilome Weed Out Plus Q or Bayer All-in-One Lawn Weed and Crabgrass Killer). Be aware it may take more than one application to completely kill this persistent weed. It's much easier to control when it's a seedling or use preemergence products in early spring.

The big point to make, with the exception of foxtail and crabgrass, is that quinclorac will not work to selectively remove tall fescue, bermudagrass, bromegrass or annual blugrass from your lawn. So identification of grasses that LOOK like crabgrass is essential before you start spraying herbicides willy-nilly.

3 comments:

  1. So how does one control or kill: tall fescue, bermudagrass, bromegrass or annual blugrass from your lawn?

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  2. Good question. Tall fescue should be removed by hand (digging) if only a few clumps are present. There is no herbicide that can selectively remove the tall fescue without harming your bluegrass. A severe infestation of tall fescue will have to be tolerated - or the entire area killed with glyphosate (Roundup) and reseeded or resodded. The same is true for bromegrass. Bermudagrass can be selectively controlled in a bluegrass lawn using either Tenacity (mesotrione) or Pylex (topramezone); it's best to have a lawn care professional apply these materials. It will require a minimum of 3 sequential applications (7-10 days apart) to control bermuda - and it's likely to return the next year because you rarely get all of it. Tenacity costs about $60 for 8 ounces, while Pylex runs about $400 (yes, $400) for 8 ounces. Annual bluegrass is very difficult to remove selectively from any turf. Total renovation of a lawn heavily infested by annual bluegrass is often the best course of action.

    ReplyDelete
  3. Very good article.
    Looks like it is annual bluegrass invading a large spot in my tall fescue lawn.

    ReplyDelete