I have battled mowing a hill for years, I finally decided to plant flowers and do landscaping where it was hard to stand up. Putting in railroad ties for steps on a hill is great. Now I can actually walk up and down the hill without rolling down. You can also see in the pictures that I put flowerbeds on either side of the steps. An arbor, simply made out of pressure-treated posts, with long bolts holding them together and then set in concrete, gives the wisteria plenty of support. When planting on a steep hill, you have to make sure everything gets watered well until established as rain runs off a hill so fast it doesn't give the plants the water it needs. I also have juniper shrubs on another hillside that help with erosion and that's another area I don't have to worry about mowing. I actually have raised beds on some of my slopes.