I am a homeowner and ripped out my old yard (weeds) and regraded with top soil from a local supplier and seeded Pennington Sahara Bermuda. The Bermuda is starting to fill in, but the top soil was contaminated with Nutsedge and this weed, which I haven't identified. It grows with a THICK root and spreads fast. I have mowed the grass 3x times now. When would it be appropriate to put some Sedgehammer down and some herbicide for this unknown weed? Thanks.