On 7/4/10 2:00 PM, hr(bob) wrote:
I have the invasive grass/weed shown in the picture in many places in
my lawn. The spots of weeds pop up with no apparent source. They do
no respond to weed killer, and they crowd out regular lawn grass. I
am in the Chicago suburbs. Can anyone tell me what the grayish green
grass/weed is and how to get rid of it?

http://www.flickr.com/photos/bobhofmann/4761771580/

Thanks,

Bob Hofmann

Looks like crab grass. If it is, note the following --

Crab grass generally indicates a lawn that is getting too much water too
often. If the summer rains are not sufficient, irrigate deeply and
infrequently. Try irrigating only once in 3 or 4 days. When you do
irrigate, cut the time in half and then irrigate twice with an hour
between; more water will soak into the soil instead of running off.
Adjust the duration such that, on the day before you irrigate, the lawn
(other than the crab grass) is not wilting.

There are various brands of lawn food that contain a herbicide that is
specific to crab grass. The herbicide can be toxic to animals,
including humans, if too much is applied to your lawn. Thus, avoid
using too much at a time; and don't use it at all if the amount of crab
grass is minor.

--
David E. Ross
Climate: California Mediterranean
Sunset Zone: 21 -- interior Santa Monica Mountains with some ocean
influence (USDA 10a, very close to Sunset Zone 19)
Gardening diary at http://www.rossde.com/garden/diary