I admit I'm no lawn care expert so please correct me if I'm going wrong here. I'm trying to strengthen up the roots of my grass since it has been neglected. Did a little research that said to put down a high nitrogen slow release fertilizer after the temp is consistently below 50F after top growth stops but before the ground freezes. I just cut my grass last week for the last time. Guy at the store said I'm way too late though and I'm only going to encourage top growth. What's the right thing to do here?