My back yard has an approx. 4ft retaining wall as there is a tall hill behind our house.The soil is very hard clay that is hard to keep moist. I would like to plant something on the hill for esthetic reasons as well as to make the hill more stable(gets washed away each spring from melting snow). I had planted wild flowers last year which are doing okay but is there something better? Ornamental grass perhaps. I don't want to look at the dirt anymore!!!

Very few plants can grow in very hard clay, especially where the water just runs off & cannot retain moisture. Therefore, you simply have to amend theb soil before planting anything, so as water & air is present in the soil. A suggestion is to amend the soil to a depth of at least 6 inches, (approx) 2/3 soil that is there & /1/3 mixture of peat moss composted manure & coarse sand (one part each) & mix it all together. Then in Sept, (earlier the better), seed a mixture of 1/2 Fall Rye, & 1/2 Crown Vetch & water in with fine spray. The Fall Rye will dig its roots deeply into the soil. The Crown Vetch will eventually take over. It has pretty pink white flowers & spreads quickly.