Underneath trees and in between homes has the worst grass growing effect. The reason behind this is shade. When you lay down seed, not only does it fill in bare spots, but it also thickens the grass. Fall is the best time to plant fescue seeds, because the young grass will suffer less heat and disease stress. Plant fescues when fall temperature reach about 75 F. The next best time to plant fescue seeds is when rising temperatures in spring reach 60 F. Summer isn't a good time to plant fescue lawns, because fescue grass tends to go dormant during periods of high temperature.