Last summer I had my yard dug up to replace the house sewer line. The ground has settled, I'm almost finished leveling it. Whew - it's all clay! Once level, I'll have topsoil trucked in and spread on the clay. What grass seed should I use? It's under a big elm and half the lawn was in heavy shade, some in partday sun. The old lawn grew beautifully before it was dug up. I wish I knew what was growing in my backyard, I'd like the same thing. Unfortunately, I'm not good at identifying lawn species. Also, when should I seed the backyard? I'd like to do this right and do it once!