There is every chance that a box of seed is full of weeds. It even says so on the side of the box. There is a percentage of Weed Seed and a percentage of Other Crop. For boxes you buy at the local store, those numbers are small, but often significant, because some weed seeds are the size of dust. If you buy online you can find seed where the Weed Seed and Other Crop total 0.00% of the contents. Seed is one place where you get what you pay for.

Which grass do you want to have, bermuda or St Augustine? It is much easier to go with St Augustine. That's what I'm doing with my lawn, but this is your lawn. Your preference will affect the choice of herbicide and approach to this question.

Also, where do you live?

DCHALL,

Thank you for your reply. Grass is mostly bermuda and that's my preference. However, i'd be curious to hear what your recommendation would be for each?

Thanks again.

If you want to keep the bermuda, you will have to kill the St Augustine. You can do that by mowing low, 3x per week, and spray with almost any herbicide except those with atrazine.

If you want to keep the St Augustine, simply mow at the mower's highest setting, water only the St Augustine and runners, and fertilize only the St Aug and runners. Spray around the runners with an atrazine herbicide 2x per year. Fertilize with only the St Aug with organics once every 6 weeks during the growing season. The St Aug should become more dense than anything else, thus choking out other weeds.