If the stem is triangular when you roll it in your fingers it is probably nutsedge. I'm in NJ also and have had it. It is usually a lighter green and grows much faster than the grass so it is easy to spot. Do you have any photos of it growing in the lawn? Nutsedge cannot be eliminated by hand pulling and weed killers like Ortho for general weeds don't work very well. They leave roots or nuts in the ground that regrow. I bought a nutsedge spray at Home Depot and it worked very well. I don't recall the exact name but anything with the word "sedge" in it will work. The areas that had it every year were rid of it right away. I now only have a few of them around but not enough to respray again. I think a small spray bottle was about $8 so if you have a large area to spray you'll need several bottles.

Thanks. I had been wondering about nut sedge, bu the stem is more oval than triangular.

Here are a few more photos.

From the distance shot, it looks like one of the crabgrass variants (smooth crabgrass). Weed B Gone Chickweed, Clover, and Oxalis should take that one right out with a quick spot spray.

Funny. The follow up photos look like crabgrass while the first photo looks more like nutsedge! Crabgrass dies in the cold weather but you might want to eradicate it before it goes to seed. Use a preemergent next spring to keep it at bay. If you mow high and use a premerg every spring and even fall you'll get the upper hand pretty quickly.

Crabgrass.

Thanks everyone. That's what I was leaning toward myself. I've been trying to do this lawn natural/organic, so looks like I have a lot of pulling ahead of me.

I think at this point I'd forego the manual pulling and hit it with Weed B Gone as morpheuspa suggested to ensure you got it all and minimize seed spread. The WBG contains triclopyr (amine salt) as the active ingredient and is effective on broadleaf weeds. You can also use any product that contains quinclorac, which will also kill the crabgrass.

You may have to overseed/seed after treatment as it will most likely produce thin/bare spots.

Early next spring hit lawn with a pre-emergent (Prodiamine) when soil temps at 50 degrees.

Sulfentrazone and Halosulfuron can be used if you have a sedge problem.

Will

Thanks Will. We're still trying to do this lawn without chemicals, though after my experience the last few days trying to pull as much as that crabgrass as possible, the Weed B Gone became more tempting.

I have two more weed IDs I could use help with. The first three shots are the same weed. The fourth is something different (in case it isn't obvious from the pics).

You might try comparing it to this: https://www.google.com/search?q=japanese+stiltgrass

@daniel:

A nice idea....but he's going to give up within 15 minutes.....what a beast of a job.....not to mention spreading crabgrass seeds everywhere!

Good point danielj_2009. I do plan to pull it all out, but I like to know my enemy!

Like Joe said... it's a losing battle. You might get by if you use a preemergent in the early spring and then again in late August. If you mow your grass high and take care of it that will reduce weeds. I think chemicals in general have gotten a bad rap if you use them with proper ppe and use common sense -- maybe an unpopular viewpoint nowadays but then again hysteria seems to be the new normal. All IMO of course.