I am a University of Illinois Master Gardener in Clark County, Illinois.
A client asked why the grass she planted over the location of an evergreen that failed and she cut down could not grow over that spot in her lawn.
The tree was over 30 feet tall and was doing poorly when she bought the house in 2010. She is not sure what kind of evergreen it was. She had True Green spray for bugs the first year and it never really recovered. That is when she finally cut it down. She used stump rot and then eventually had someone with a machine grind the stump down.
She has planted grass seed in the winter, fall, and spring. She even added new soil and put straw on top of it. Grass came up one time, but it has since died in that area only. The most recent application was about 2 weeks ago. The impacted area is approx. 15 x 20 feet.