Are you sure what you have is crab grass? Crab grass is an annual that germinates and grows when the soil temperature is in the 60's or about 2 weeks after Forsythias bloom. While the roots of the crab grass I have pulled out are fairly extensive I'd not think them long running, that indicates to me possibly Quack Grass.

Perhaps this article from Michigan State may be of some help.

http://msue.anr.msu.edu/resources/crabgrass-control-in-home-lawns

"Long, running roots" doesn't sound like crab grass to me. Could you give us a picture of what you're fighting?

Ok, I did some research and I have Quack Grass in my garden beds. It has long white roots the run for long distances. I just don't know how to get rid of it. I pulled up some of my iris and cleaned them out but after I replanted them the grass grew back in again. It is taking over my gardens. I need to get a handle on it this year.