I have a 12,000 sq. ft. bermuda lawn that has gotten very sparse and consequently is becoming overrun with clover(yellow flowers) and dandelions. I want to reseed in May, and my question is must i kill all the existing weeds before doing so? And with what? Or will the new bermuda crowd them out?I plan to seed the grass,fertilize w/ 9-2-2 poultry,and add a thin layer of BTN. Any advice would be very welcome.