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capecodder 08-22-2012 09:20 AM

Crabgrass Overwhelming Lawn -Need Advice.
Hey folks,

Earlier in march I re-seeded a new lawn with new loam and seed. Now my lawn is overwhelmed by crabgrass. I really need some advice on what to do? Ive tried the ortho sprays that kill crabgrass but they dont really work. My lawn looked really nice until the crabgrass emerged. Can anyone give me some advice on where to go from here?

Thunder Chicken 08-22-2012 11:37 AM

Same problem here - the drought trashed a lot of lawns and the rains came just in time to water the crabgrass which didn't have any competition from the turf-grasses. This is the season for crabgrass too, it is hard to stay on top of it.

You can spot-treat the crabgrass (Roundup or handpull) until the weather cools off. This fall, de-thatch and overseed heavily with sun-tolerant grass seed, get it established before the frosts. You can apply pre-emergent (siduron/tupersan can be used while seeding grass) in the fall and next spring. If you can get the grass established the weeds won't be as much of a problem next year.

If we get a drought again, the only thing you can do is water-water-water - try to keep your turfgrass alive, green, and thick. Always mow as high as your mower can go, the grass will out-compete the weeds if it is thick enough.

user1007 08-22-2012 12:53 PM

Ditto what Thunder Chicken says but with a few things to point out.

Round-up, as purchased for home use, is a non-selective herbicide and will kill anything it gets sprayed on so be careful and apply when you have to wind drift. There are post-emergent herbicides specifically for crabgrass but I don't know how effective the ones consumers can buy are. You may need a permit or applicators license to get stronger herbicides.

Crabgrasses are annuals so will be done for the season as soon as the weather turns cool. Try to keep the plants from going to seed. This is hard because the advice to cut your turfgrasses at a tall setting is generally good. Cutting crabgrass tall can let it go to seed.

For most residential situations, pre-emergent herbicide treatment is still the best approach to controlling crabgrass and as mentioned you may need a couple of applications. They may effect germination of turfgrasses you want so definitely overseed in the Fall if you can. Just remember that while perennial ryes germinate 7-10 days bluegrasses and fescues can take 14-21 under ideal conditions. Wait until spring if that is going subject young grass plants to early hard frosts.

capecodder 08-22-2012 12:56 PM

I went out a week ago and bought a Fiskars weed puller from Lowes. I was thinking of pulling them by hand, repairing the scars with top soil and seeding heavily. Do you think this is a good idea? Or should I just wait for the crabgrass to die off and then do as you and reseed?

Thanks for the reply!

user1007 08-22-2012 01:16 PM

Getting the weed plants out of your way will certainly not hurt much if you have the time, energy and patience. Just remember that if they have gone to seed you will be knocking seed off just twisting them out of the ground.

Thunder Chicken 08-22-2012 03:30 PM

My lawn is mostly dead from the summer (not dormant, dead). So what sdester mentions about mowing is correct - if the only thing alive in your lawn now is crabgrass, mow LOW. Scalp it, keep that crabgrass from going to seed. You won't get all of it but it helps. If only parts of the lawn are thick with crabgrass, you can scalp only those areas.

When the weather cools and the crabgrass dies, dethatch like crazy. You will clear out a lot of dead weeds and the dead grass, and you will know what parts of the lawn need attention. Whatever cool season grass that is still alive will start to perk up, and you can topdress and overseed. Once this grass starts coming up, in the fall and spring, mow HIGH.

capecodder 08-22-2012 07:34 PM

Guys, thanks for the info.

I have been mowing the lawn on a low setting to keep the crabgrass from seeding. I too have some dead grass from the summer heat. I noticed your from Massachusetts as well Thunder. The last few weeks were a killer with heat and I have some areas that didnt make it.

What im a little confused about is that when the temperature cools, soil temperatures drop and the crabgrass dies off, but isnt this temperature generally too cool to allow new seed to germinate? I would like to rent a de-thatcher, seed, topdress the soil and get it to germinate before this area starts getting its first frost.

Thanks guys.

Thunder Chicken 08-22-2012 09:15 PM

The idea is that you will fill in all the open areas of the lawn with new grass established this fall. Crabgrass is an annual and will die off when the cold comes. Come next spring, the grass you planted this fall will have a head start and will get the upper hand and fill in the lawn before any crabgrass seed can germinate. If you apply a pre-emergent fertilizer in the spring, you are stacking the deck even further in favor of the grass. You may also want to do a follow-up overseeding in the spring to fill in any spots that didn't make it through the winter.

This is a website I like that has a good plan for general lawn care:

I use pre-emergents sparingly, only if the lawn is in really bad shape and I need to keep the weeds from getting the upper hand. If the lawn is healthy weeds won't be a problem.

SPS-1 08-22-2012 09:33 PM


Originally Posted by capecodder (Post 994038)
I went out a week ago and bought a Fiskars weed puller from Lowes. I was thinking of pulling them by hand,

I use needle nose pliers. Works great. You can push the tip into the dirt enough to get the roots, and you can select exactly the crab grass, and leave the bluegrass alone. It was intimidating at first --- you pull and pull and it seems like you are not making any headway. But it worked. I attacked it as soon as I started seeing it. The weather has been better recently, and the bluegrass is filling in. Sounds like you have a lot more than me though.

pwgsx 08-23-2012 09:06 AM

What kind of grass did you plant? MSMA is the only way to kill crabgrass, although it is not sold in stores anymore but you can find it online or if you know a farmer he can get it.

SingleGuy 08-23-2012 03:05 PM

I can't offer much more advice than already given but what I do on my lawn is to make sure my grass ( turf type fescue ) is cut between 3 -4 inches so it helps kill any weeds. I apply a pre-emergent twice a year ( I live in a transition zone ). and I apply a post-emergent. I overseed at least every 3-4 years to make sure my grass is thick and strong.

I make sure my soil ph is where it needs to be because most weeds love low ph and grasses suffer in low ph; It's a win-win.

I have been known to pull weeds but as others have stated, it's risky because you could end up knocking seeds onto the ground or into the air. I'm not usually concerned though since I use pre and post emergents.

Hope that helps.

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