Guys, I do have a question. I put down Halts in mid-April this year. Worked amazingly for crabgrass, but I still got tons of poa annua by mid-May.

Did this seed germinate in the spring, or were these plants the ones that germinated last fall?

This post was edited by GrowSomeGrass on Mon, Jul 14, 14 at 13:21

I can't answer when they germinated. You do want to put down a pre-emergent in the fall and spring. I'm not sure of the temperature. I would Google to see at what temp it germinates or someone else will answer. The one thing I am sure of is dimension works. I had a huge poa problem the last few years to the point I was thinking about using a lawn company and I have ALWAYS been a dyi person. I used dimension from Lesco and I had no poa at all this year. You can get it from a John Deere store or home depot carries pre-m which is supposed to stop poa. Good luck and hang in there. I know it is extremely frustrating.

P. annua can germinate in spring...or fall. I make sure to have a pre-emergent shield down during both periods. I use Prodiamine (Barricade), so it's not difficult to get 9 months of control with one application.

That helps a lot.

Tenacity can be used for control, but several applications are required and control isn't perfect. Still, it's reduced my P. annua problem from epidemic to six small spots this year, dead by early May.

Morph is right, it germinates in fall and spring, but mostly germinates in fall, it seeds heavily in the spring and those seeds then mostly germinate in the fall. Pre-m this spring does nothing against all the poa a that sprouted in the fall and over wintered and then produced those ugly seed heads. You want to worry about soil temps, not air temps. In Mass I would make sure your pre-m is down before Labor Day. Year around pre-m will help reduce your poa a. Tenacity can be used for post emergent controll like morph said too

Thanks everyone for their help. Yeah, in the spring, I let my lawn grow long for 2 weeks. And you should have seen it. There were millions of POA seeds. Millions. Thats when I realized I have a massive problem.

The POA however was originally a much lighter green than the rest of the lawn, but has now blended in quite nicely. The lawn to me looks uniform. But I can slowly see some patches starting to take stress from the heat. I will post a pic.

So I will definitely put down Halts in early - mid August. If all those seeds germinate, my lawn will be wrecked next year. Thanks guys.