I have a shady slope on one side of my house about 45 feet long and 8 feet deep. It is a side that is fairly hidden and isn't seen much. I would like to put something fairly cheap on it that will control erosion and look pretty good.

I am thinking of using Liriope Spicata rather than Muscari because it would be more economical.

If I were to dig a trench and fill it with cement around the perimeter of the slope on three sides (the house is the fourth side) to prevent the underground tubes from spreading, how deep should the concrete be poured? Six inches, 12 inches??? I know there would be some root issues because I have a large tree.

Thanks