Here is the photo:

Knowing something about sedges can help control them. Sedges evolved in wet lands and grow best in our lawns that are failry consistently wet, ie sprinkled every day. Sedges have evolved to grow in fairly dry soils, once established, but I see them growing mostly in lawns that have systems that water the lawn daily. Others report differently.
The sprays used to kill nutsedge (same as the crabgrass poisons) will also kill off the grass you want growing. The best means of control I have found is mechanical removal making sure you also get the root and the nut shaped underground portion that will regrow if not removed.

Here is a link that might be useful: About Nutsedge

Agree with kimmsr. If you allow the soil to dry out between waterings, you might be able to kill it off. We talk about a watering regimen that is deep and infrequent. Deep means 1 inch all at one time. Infrequent means monthly in the cool months transitioning to as much as once every 7 days in the hottest heat of summer. If you live in the low desert west of Banning you have a different situation.

Where are you in CA?

For reference, we're in Sacramento.

Since the sod is pretty new, I thought it's not a good idea to let it dry out completely yet. Don't I have to slowly teeter off? If so, will the nutsedge take over since it's given optimal conditions for a while? Will it kill off my new sod?

If this sedge is growing in your newly laid sod, and was not there before, I would go back to the sod supplier and have them fix this problem.

Yes you should taper off on watering until you are watering only once per week in the hottest heat.

What kind of grass did you buy?

Kimmsr has a point about your sod supplier.

This post was edited by dchall_san_antonio on Sat, Jun 15, 13 at 13:24

I have been battling nutsedge for about 10 years. I had fill brought in at my rear property boundary, and within 10 years it has spread to my St. Augustine front yard - 130 feet away - via side yard landscape beds. They do spread via rhizomes, sometimes very deep which is impossible to dig up without disturbing your sod. I only notice it when the grass gets long - I am ready to wave the white flag on this weed and just let it do its thing.

By the way, I don't have an irrigation system, so my grass is only watered during rain events and is very rarely saturated. The nutsedge has still been relentless in spreading.

I understand spraying with horticultural vinegar may help. As well as pulling the grass when it is small (the larger the leaves, the larger the "nuts" and therefore more food available for new rhizomes.

As they said, avoid overwatering. This is a good start. However, you must pluck often! Go out every few days and pull them up. Get your fingers as close to the ground as possible and tug. Hopefully you can get the nut that also grew and is the fuel for the next generation. It may seem futile after a bit, but each pulling gives them less energy to regrow as long as it can't get traction with new shoots in the sunlight. Eventually, after a few repeated pulls, they'll run out of energy then die. Next year, if the sedge is still active, and your sod has established its roots in the soil, then you can try a more aggressive treatment. The key is to follow up to get the tubers that will spring up afterwards. It's a war of attrition! Some have made claims about molasses, but it can't be replicated with any great sucess in a study.

And you can forgo the gym membership. Nutsedge pulling is your new workout! :p

Here is a link that might be useful: UofA Nutsedge Control in Turf

This post was edited by eline65 on Fri, Sep 6, 13 at 11:38

Sedges evolved growing in marshes, bogs, wetlands, but have adapted to growing in dryer areas although they do need a relatively moist soil to get started in. Sedges spread by seed as well as by rhizomes (once established from seed) and roots and most all lawns that are well tended will have enough soil moisture for them to get established and grow.
None of the sprays that will control sedges are acceptable to a true organic grower and vinegar will only kill off the top growth, although if that is done often enough the "nut" they get their name from will die also.
If molasses did kill the Nutsedges then it would kill every other plant it was sprayed on as well.