I am surprised--crabgrass around here is looking very brown. Not dead but looking very much on its last legs. Lowest temperature has been 41 degrees. http://www.enviroweather.msu.edu/run.php?stn=hvl&mod=w_sum I suspect that after a temp of 45 degrees, crabgrass is injured so that almost zero new growth is possible. What does your crabgrass look like? Got pictures? Does this mean you could have sown grass on top of crabgrass two weeks ago? And your new grass would come up through the dying crabgrass? Does this mean you could fertilize about now without stimulating any growth from crabgrass?