I'm completely confused so let's start with the basics.

Where do you live, specifically? You said N. California but I'm guessing northern Central California with the look of your lawn - Sacramento?

Do you know what kind of grass you have? I don't see anything that looks like crabgrass or the remains of crabgrass. Crabgrass is a summer annual plant that cannot survive temps in the low 30s. It is easy to get rid of but not if you're watering and mowing wrong. The picture looks like dormant bermuda grass, but if that really is dead crabgrass, then I do see your problem.

How are you watering? How often and for how long each time?

How high/low are you mowing? Really need to know what kind of grass you have for this answer.

What kind of sod did you use in the back yard?

How often do you fertilize and what do you use?

Do you use herbicide, insecticide, or fungicide?

@ dchall_san_antonio:

I live in San Jose, CA.

I believe its some type of fescue grass. I over seeded with dwarf fescue a few years back in the fall and the lawn was beautiful until summer came...then whatever is taking over, took over. The crabgrass (if indeed it is) took over and it's back to square one.

I currently water x 2 week for 15min ea session at 4am. I mow at a high setting and right now x 2/month.

I'm attaching a closer shot of the lawn to see if it makes this a bit more clearer.

I installed dwarf fescue in the rear yard and it's been really nice for 4+ yrs.

I fertilze per the schedule that I tend to see here in the forum. Twice in the fall and once or twice into the spring as well.

Don't use anything else (herbicide etc).

Thanks again.

I have this same geography issue with the residents of the Dallas-Fort Worth area. They refer to their region as North Texas. I used to live in the Texas Panhandle about 300 miles north of them in "North Texas," and I can tell you Texas goes much farther north than Dallas. San Jose is not N. Calif. San Jose is "Bay Area" Calif. N. Calif starts just south of Redding. I realize you hear Northern California on TV all the time, but someone needs to look at a map. Back when the speed limit was 55, it was a full day's drive from SF to Oregon. That should tell you you're not in the north. But anyway...Bay Area is much more helpful because your climate is different from either Sacramento or parts further north.

All the dormant stuff appears to be common bermuda. Some of the green stuff appears to be common bermuda, too.

Both your watering and mowing are at the wrong ends of their respective scales for the grass you have. I'm basing this on bermuda, because that is what you have the most of. This time of year no matter what grass you have, you should be watering once per month for longer than 15 minutes. Having said that, some sprinklers can put out enough water in 15 minutes to measure a full inch, but not all. Time how long it takes your sprinklers to fill several cat food or tuna cans placed around the yard. Every system is different, so this is something you have to do yourself.

Since bermuda is now your dominant grass, you should be mowing 2x per week at your mower's lowest setting. If you had fescue then you could mow at the highest setting, but fescue is too weak a turf to compete with bermuda.

If you want the bermuda to look its best (ahem), then fertilize with a high nitrogen fertilizer every month. There is a variety of bermuda which really does look great, but you don't have that one.

Now to get back to your original question, you can kill bermuda with RoundUp spray. If you want to put in a fescue or Kentucky bluegrass lawn, you should really wait until next fall. If you try to renovate in the spring, two things will happen: one is the crabgrass (real crabgrass) will be the first grass seed to sprout. Second is the new grass which does germinate will be too weak for the summer heat and will die out in July...leaving you with the original crabgrass. If you want to put down sod, you can do that in the spring with much better results.

I would recommend you take great care of the bermuda over the summer and start in August to do the renovation. Then the bermuda will be growing great and will die much better with a couple applications of RoundUp.

As far as watering the rest of the season, wait until the temps rise into the 70s before going to once every 3 weeks. When it gets into the 80s, go to once every 2 weeks. With temps in the 90s, then go to once per week. If you get a period of several days above 100, go to once every 5 days and get back to once every 7 as soon as you can. The problem with frequent watering is the weed seeds LOVE that schedule. But if you allow the surface of the soil to dry completely before watering again, then the weed seeds cannot get started.

And I should note that all your late winter and early spring weeds have already sprouted. They sprout in the late fall and lie dormant until the days start getting longer. Treat those with a spot spray of something like Weed-B-Gone for the broad leafed weeds. Killing grassy weeds in a grass lawn is harder, but with bermuda, you can take a tough love approach and the bermuda will be back in a few days.

I have this same lawn in my Sacramento backyard. It is kikuyugrass; brown each winter and then gang busters all summer. The kids love it because it so dense in the summer, like a thick carpet. I've been told the only remedy is to completely kill it - Round up - remove EVERYTHING - then replace with sod.

Here is a link that might be useful: Kikuyu info from UC ag extension office

There is an outside chance this is kikuyu, but we would have to have stolons pulled from bermuda and kikuyu to know. Kikuyu is a very rare grass to find in normal home lawn unless you live adjacent to a highway where they used it for erosion control. Now that I think about it, there is another outside chance it is zoysia. The only thing I'm fairly certain of is that it is not St Augustine. All of these grasses grow very dense in the summer and turn brown in the winter.

California has a drought, please , those of us who conserve water are not worried because we have brown lawns, please jlcjlr and jvmagic don't waste water on a lawn, reconsider replacing your lawn at this time of drought