I get the impression you live in a country setting.* How about some type of native groundcover for that hillside?* Got any pics of the hill?* What type of sun conditions?* Would a mix of shrubs and groundcover work or would that be too much for the space?* The benefit of adding shrubs to a steep hill is the different heights of the plants and the different size of the leaves slows down the impact of the rain drops, hence less erosion.
Newt
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.