I know it is preferred to plant them in the fall, but I can't wait because I need them for erosion control on a hillside bordering some steps I just got poured. We will be filling it back in on the sides with some soil mix and I read lilies are really good for hills.

Also, I have some odds and ends I can plant mixed in with them, anything to get something going ASAP besides grass (don't want that) so the fill soil won't wash down to the sidewalk which it will if it rains, then I'll have to scrape and shovel it back up as best I can. We will tamp it down as best as possible and also would it be a good idea as a temporary measure to put some bricks and stones at intervals until some plants get establised?