I live in a community whose ground is dominated by shale. Any digging requires pick-axes and heavy lifting over chunks of clay. Consequently the ground is hard as concrete and resists reseeding. I have spent the spring attempting to fill bare patches of my lawn: the blanks are both veritable holes surrounded by grass in some spots and simply bare spots in others. Some of the seeding has taken--but only after two applications of seeds or more with much digging and scratching of soil--and others (also with reapplication) places it has not. Much of the latter is in areas of full sun. Some of the problem is thatch-related, others not. The ground was recently aerated and I've been working on dethatching.

I'm close to my wit's end (admittedly a short trip, to be certain). And short of major surgery I can't think of next steps or causes.

Does anyone have a cure? Is it the seed (Rebel; if so, can someone recommend an alternative)? Is it the full sun? What am I doing that I should stop doing, what am I NOT doing that I should be doing?

Many thanks.