Fond memories of a Lady Banks the grandparents had meticulously trained over their lattice arbor in Oak Cliff inspired us to try it in a couple places when we moved to Dallas. First one I toasted trying to espalier it in a dry bed on a shadeless south facing brick wall... proving they can be easily killed given a brown enough thumb. Second one thrived with 6+ hours of summer sun on the north side of a wood fence for 9 or 10 years. We took it out when we converted the pool beds to deciduous/less dense plants to deal with drought and duck problems, though probably would have gone anyway due the growing effort needed to keep contained and looking good in the space we had for it. Would use it again in a minute in the right location.

If you live in New York as suggested in your name, you might want to search on cliffandjoann. They built a stunningly beautiful pond and have explained the details. They say that some of their plants are in pots. I use impatiens and am under the impression that they will grow without much actual soil. It is certainly true for water cress (from the grocery store) anchored directly in flowing water. For something larger, sweet flag will certainly work. You can also use vines or other plants growing beside or near the area. You can also add logs or other natural materials for interest and coverage.

Toolbelt- I love the RBU theory !! I'm stealing it! This is our second year together and first garden together. He asked if I needed those square linking tomatoe cages @ $10 ea. Now that they're up and have plants inside he said they're neat and sturdy. Hahaha! I am lucky that he rarely questions my purchases and I don't question his. BUT if he ever says anything again, I now have Toolbelt to thank for the RBU ! Oh, you want a new motherboard? Well that's 15 RBU's. LOL Alameda- if your SO doesn't already have those square tomato cages, it would be a great gift for a veggie gardener :D

For perennials I would recommend you fork the slope and then "mulch" with mushroom manure. For annuals I suggest you spread a couple inches of mushroom manure or manure and then till with a spade. At the bottom of the slope leave a furrow to collect any soil that will seep down the slope. Mulch as soon as you plant using bark or wood chips. If in your area you need to use lime, you'll probably need a little extra for bark and wood chips. Don't run equipment on slopes steeper than recommended for that equipment. I believe it's 15% for riding mowers. From my experience mulch will hold on a steep slope. It's only stone that will tend to move.