Before I go on with my questions, I understand this may seem to some veterens like a very vague and broad question. Just for the record I used CGM on my best properties this year and it worked very well despite its high cost. From what I understand, cgm prevents new seedlings from forming a root. Is this how all pre emergents work? Is cgm even a pre emergent or should it be considered to be a root pruner? Which brings me to my next round of questions, what are the ingrediants in weed n feed that act as the pre emergent and how does it work? Are either of these products similiar to Preen's garden pre emergent from those little shaker containers in garden centers?