Answer: To some extent this depends on how steep the slope is. However, you might be able to smother the grass in place and plant through it. This way you preserve your top soil and the grass helps provide organic matter to the soil. To do that, layer dampened newspaper four to ten sheets thick over the area, being sure to overlap the edges so no light penetrates. Top that with a generous, thick layer of organic mulch. The mulch hides the paper and holds it in place. After a few weeks the grass should be dead enough that you can plant. Pull aside the mulch and dig your planting hole through the paper to plant. The mulch and paper should prevent weeds from coming up in between your new plants, but do weed as necessary and keep the mulch topped up to a layer of about three inches thick. You may want to stagger the project, beginning at the top of the hill and working sideways in strips. As the new planting fills in, begin another row. Or, you may want to terrace the area with boards to help hold the mulch in place and slow runoff while waiting for the new plants to fill in. I hope this gives you some ideas.
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