Since I have a bad back, getting down to pick weeds in the garden beds is getting to be almost impossible. I started using Preen last year to see how effective it is, and although it has to be reapplied eventually, it seems to do the job very well. My question is, does anyone know exactly how this works? I know it prevents the seeds from germinating, but does it actually kill the seed forever or does the chemical wear off and then allows the seed to germinate eventually? I'm just wondering why it has to be re-applied in another 2 or 3 months. The downside of it is that I have always sown annual flower seeds in the beds but now I won't be able to do that. I'm going to try to start them in pots and plant them, I'm wondering if the Preen will keep them from thriving?