I know preemergent will keep a seed from germinating... but will it actually kill the seed? i.e. put down pre-emergent, keeps seeds in soil from germinating... pre-emergent wears out... is the seed still able to germinate in the proper conditions or has the seed expired? Thanks... Specifically, I'm thinking about Poa Annua. I have a few larger patches that I need to eradicate in 2010, and am trying to think of my 2010 plan. I'm planning on just using ROUND UP on the spots in early Spring before seed head formation... reseed these spots with a 50/50 Rye/KBG blend... hit the lawn with a late summer pre-emergent application through fall 2010 with the hopes that I don't get the patchy light green/darkgreen, look I get in the fall that I have now in these areas.