For Zone 5 we're pushing late, but fortunately most of MA will have a much longer fall than portions of Zone 5 I could name. :)

Crabgrass dies at frost, so it's actually not terribly troublesome--it's the fact that it's probably already dropped thousands of seeds that will cause the problem next year! Getting down a good pre-emergent when the forsythia blossom and keeping up the shield through August is critical.

You can either purchase a long-lasting pre-emergent like Barricade, or re-apply shorter lasting shields like Dimension to maintain the layer. Be careful and read the bag or bottle--Barricade is also available in shorter duration. I use generic prodiamine, mix it myself, and apply as a spray.

For right now, you can certainly kill off the crabgrass if you want. Any over the counter crabgrass post-emergent should work fine (I have a preference for Weed B Gone with Crabgrass Control, but it's really all the same thing).

If you wish to reseed, do so as soon as the crabgrass fades (this is pushing it, but you're really running out of late summer fast). Post seeding, use your irrigation system to damp the seed two to three times daily, morning and evening at minimum. A mid-afternoon cool off and dampening certainly helps a lot! Ten minutes per zone is usually good enough, but if your system is particularly high output you may not need that. If low output, you may need more.

Keep that up until everything sprouts (KBG takes a full month, fescue and rye only two weeks or so). Then slowly cut back, first once per day, then every other day, making the shift around weekly. Rainfall counts, so you can skip those waterings.

Next year, keep that shield up and feed the grass on schedule (May, September, October, and a winterizer if growth stops later than October 20th). Good thick grass won't allow crabgrass to grow.

Pro tip: Mow your grass long to discourage growth of all weeds, including crabgrass. I keep mine at 3" and have zero weeds.

What is dabra verna? Google doesn't seem to know.

What is your lawn grass? Is it fescue or Kentucky bluegrass, or a mix? What do you want it to be? Do you have much shade?

Getting the proper moisture on the grass blades when applying a granular herbicide is 95% of the problems with those products. You're much better off using a spray type herbicide. Then you can spot spray only the weeds and not condemn the entire yard to the herbicide. Your soil will thank you for not broadcasting herbicide everywhere.

Crabgrass dies by itself in the fall. When it dies, rake it out and seed immediately.

How do you water? How long and how often? And back that answer up to last spring. How were you watering then? Usually crabgrass only gets started in thin lawns which get watered too frequently. For Kentucky bluegrass lawns, they don't get thin like fescue does. Fescue should be reseeded or overseeded, every fall when it thins out. If you don't then it will be thin until some weed encroaches or until the following fall when you finally seed it. Don't wait until spring to seed fescue or KBG. That is a sure fire way to get crabgrass all summer.

Okay...Google suggested Draba verna. That seems to be a wildflower from the PNW. I would think Weed-B-Gone would take it out. Read the label. Weed b gone will not touch your grasses or the crabgrass. It only works on broadleaf weeds.

I see morph posted the same time I did. Just to clear up what we said, Weed b gone makes many products. Get the one with crabgrass killer and you should be able to kill both weeds at the same time. I don't get weeds like that, so I'm not up to speed on what's sold where.

thanks.

I think I have KBG and fescue mix.

I didnt water at all, other than with a hose before applying the fertilizer (and apperantly doing it wrong too)

I only installed the sprinkler system last week, so till then, the mercy of the gods.

Apparently the Gods gave you perfect conditions for crabgrass. The grass gods did that for a lot of people this year. It's getting late for me. Search this form for "deep and infrequent" to get the scoop on how to water a lawn.

What is