Question
This spring my son thought he'd help out by fertilizing the lawn while I was away (it was a nice thought which I did appreciate!) but unfortunatly, set the spreader so the fertilizer came out and covered the lawn like snow. The grass turned brown and was almost completely dead. I threw out some grass seed on it and it took, but now most of the lawn is INFESTED with either crab or quack grass (I can't tell which). Did the ph level change cause this? And how on earth do I get rid of it?! Please help! Our lawn was beautiful and now looks just awful.


Answer
Based on timing, I expect that the weed is crabgrass. Grabgrass germinate from seeds which drift in or are left from last year. The seeds germinate in late spring but are often crowded out in an actively growing lawn. On a dead  lawn the crabgrass has free room to spread. The plants become visible in early summer and will grow large throughout summer and then set seed and die with first frost. You can wait until early spring and then apply a PRE-EMERGENT HERBICIDE such a Scott's Turfbuilder w/Halts (crabgrass prevent). Apply in early spring just as the forsythia bushes flower. Do not postpone too late.

The existing crabgrass plants will die with first frost but the pre-emergent herbicide will take care of their seeds. If you apply this, you can not sow grass seeds next spring (wait to fall).

It is impractical to fight crabgrass now; short of handpulling.

pH does not affect weeds.