I have a large area in my lawn what is about half centipede grass and half crabgrass all mixed together. I am trying to find something that will kill the crabgrass without killing the centipede grass. I have read that a product called Sedgehammer (formerly Manage) works good on nutgrass. Will it also work on crabgrass without killing he centipede. I know Roundup is good for killing crabgrass, but it also kills the centipede so that is out. Any other products out there that will work without also killing centipede? Any advice will be greatly appreciated.

If the temperature does get cold enough where you live in winter, allow the crabgrass to die from the chill. I understand you have centipede grass so I assume you live in the southern portion of the US. But since crabgrass is an annual weed it will only last for one growing season as it sets seed for future crabgrass, to your chagrin. Once it dies thoroughly rake it from the lawn after mowing your grass (when you do your last mowing of the season) to its lowest ideal height, one inch, in late fall to late winter, before soil temperature reaches 55 degrees (if it ever drops below that). When the soil reaches about fifty-five degrees apply the pre-emergent herbicide corn gluten to the entire lawn. This will kill any lurking seeds in the soil that will soon germinate. After about four weeks or more you are ready to reseed. Carefully read the label of the corn gluten to know when it will be safe to spread your grass seed.

Once the soil is clear spread about one half inch even and loose layer of compost over the entire lawn (not just the bare spots, for compost will fertilize all the lawn). Apply a starter fertilizer lightly to the bare spots only and then spread the seed. If you want a thicker overall lawn apply the starter fertilizer and seed over the entire lawn, Just remember to apply the seed more heavily in the bare spots. After seeding gently rake it in about an eighth of an inch to where about fifty percent of the seed is exposed. Immediately water your lawn and keep it evenly moist until most of the seed germinates, about twenty days or more.

If you mow, water and fertilize your lawn regularly you can keep crabgrass from resprouting. Also, allow the grass clippings to fall on the lawn as fertilizer. You may not need to buy fertilizer all year, for centipede grass needs little compared to other turfgrasses. I try to first take the most environmently friendly approach before any alternative solution. :D