Welcome to New England! The Maine gardening forum is often kind of slow, so if you don't get answers you are looking for you might try the New England forum which is fairly active. How large an area is this and how steep is the hill? Do you know the zone? Maine covers a lot of zones; you can use the map linked below to find your zone if you don't know. What is the pattern traffic like? Do you walk anywhere across a broad slope, or are you more likely to walk in a narrower band? How much sun is part shady? Is there enough sun to grow grass? Would you consider adding some shrubs to focus where folks walk and then adding some rustic steps or water bars to help divert the water? Is it possible to divert some of the water before it gets to the slope with a swale to reduce the flow down the slope? Here's a website from the Maine DEP that has a bunch of different suggestions for erosion control and plants for use with lakefront properties such as infiltration steps and water bars. http://www.maine.gov/dep/land/watershed/materials.html A photo or two that includes the area in question as well as what is above and on either side of the slope may help answer some of my questions. IME there aren't many ground covers that will take heavy foot traffic that will also tolerate part shade and high water flow, and if you walk here regularly, it may be difficult to get something established. There are shade grasses that might work, especially if you could keep folks from walking on one part of the area you are working to establish for a full growing season, so that one year you do one part, and the next year you do another part. We have a sedge that grows wild in areas of mostly shade to mostly sun, Carex pensylvanica. It will take occasional foot traffic when established, but not heavy foot traffic, so you would also need stepping stones. You would want to get flats of plants if you decide to go this route. I don't know if the place below sells to the public if buying in quantity, but I imagine that there are native plant nurseries that sell in quantity. http://www.northcreeknurseries.com/plantName/Carex-pensylvanica- Partridge berry AKA Mitchella repens is another native groundcover, but like the sedge wouldn't want regular traffic and would need stepping stones. Here is a link that might be useful: Maine plant hardiness map

One of your first goals will be to slow the water sheeting down the surface, both to reduce erosion and to increase the amount of moisture that soaks in. If you can afford someone to put in a few boulders that you can plant between, that might help. Even chunks of cordwood slightly set into the soil will help and can be left to rot or get covered by the mulch and plants. Use this sort of a shape if possible \__/ (sort of a sideways C with the opening facing into the hill and dug into the slope. You'll want to put down really fibrous bark mulch to help hold soil and reduce runoff while things take root. Another option DH used to hold a very steep slope was getting long wooden stakes (grade stakes) and pounding them into the slope perpendicularly to the slope to brace boards that help hold the mulch and soil while the plants established. Grade stakes are pretty inexpensive and he used slabs (cutoffs from the outside of a tree) from a small-scale sawmill. This wouldn't work with rocky soil, but we have no rocks, so if that's your situation it might help and is inexpensive. I think T2D's slope is a bit steeper in person than it looks in some of the photos, particularly on the far side of the steps. I agree that those beds are stunning! I have a quite steep bank behind my house (SW facing) and at the time I planted it had little time or money to deal with it. I did have a bunch of old orange daylilies crowded into a bed where I wanted to use the space for something else, so I transplanted those about every foot or so and they hold the soil well and have spread. (You may be able to get a bunch of these by offering to dig them on Craigslist or by just looking to see if someone posts that they are available.) I also got another medium height plant that spreads from another gardener (no idea what it is - screaming magenta daisy-like flowers and large coarsely toothed leaves) and the two weave around each other. I put a Korean spice viburnum (V. carlesii) a few feet up from the bottom of the slope and it has done well. A Kousa dogwood is at the bottom of the slope. I mulched it well and renew the mulch every 4 years or so. I'm only now starting to consider what else I might want to plant here, so I'll enjoy seeing what others suggest. When I plant on a slope, I take the extra soil from the hole and use it to make a wall below the plant and create a pocket to help hold water. As far as other specific ideas you mentioned above, you might want to reconsider the wildflower seeds as they tend to need a lot of weeding to get established, need sunlight to sprout (so no mulch) and may well wash to the bottom of that steep a slope. I'd put the Siberian iris near the bottom of the slope as they like it a bit less dry and may need dividing in a few years to bloom well. Bearded iris will tolerate dry soil, but won't help much with erosion as their roots aren't very deep or prolific. Sweet fern will do well anywhere on that slope as it will grow in any poor site IME, but it will sucker and spread, not remain just where you put it. It hasn't been difficult to pull out when I've needed to. I have a white-flowered 'Jet Trail' quince that suckers and is in a relatively dry situation (at least it never gets supplemental water and the soil is sandy.) It seems to top out in height at about 4 feet, but I have to periodically whack it back to reduce the girth as it gets more than 6 feet wide. Some other ideas that occur to me for your situation: Think about sumac - either one of the fancy kinds like fern-leafed or lowgrow or even plain old staghorn. It will sucker also, but is pretty unfussy and likes full sun. Birds like the fruits and the fall color is stunning. Junipers - come in different textures and colors The shrubby Caryopteris have lovely late summer purple-blue flowers. They are low growing and some have variegated or golden foliage, though the original types have bluish foliage. Many bulbs like to be drier in the summer, so they will help add interest in the spring and the roots will help stabilize soil. (daffodils and tulips would be a good start.) Nepeta and Russian sage come to mind as plants that will be OK. Ice plant will work if it's a kind that's hardy enough for you. The western Penstemons or Agastaches like it dry. I planted Agastache rupestris on a steep slope as well as Penstemon pinifolius (pineleaf beardtongue) along with some hybrid forms of both kinds and they have survived most years though they are borderline hardy here. Achillea and lambs ears are happy where it's dry. Look at High Country Gardens website for ideas of plants that like dry and sunny. I have found that many of the plants they sell (like the Penstemons and Agastaches) will grow for me on steep slopes. They tell you what is the precipitation range for each of the plants, but in steep areas I find I can plant things that like it a bit drier than my area is. Regardless of what you plant you will probably need to water some the first year if there isn't regular rain so things have a chance to get established and grow sufficient roots. Soaker hose below the mulch will help with this without increasing erosion potential. Here is a link that might be useful: High Country Gardens

At first look, I would say no, it is not possible to stop this rather severe erosion by vegetation alone. Some sort of engineered solution will be needed. Is this a part of a stream system? Is there any chance of state grant money to assist in a project to repair this site? You might be surprised at what is available, depending on where you live, of course. More likely than not, the only realistic way to mitigate this problem would be to regrade the slope-get it to a 2 to 1 or lesser slope. Then, vegetation will be needed to finalize the stabilization. This can and should consist of a combination of seeded, plant plugs, and maybe even live stakes, all to help hold things together. I've been involved in several large-scale restorations of severely eroded ravines. I'm guessing that urbanization upstream from where this picture was taken is causing that waterway to become "flashier" than it originally was. IOWs, when a heavy rain event takes place, or even a moderate one, increased presence of roads, parking lots, rooftops, etc. on the upstream side is causing too much water to be immediately drained off into this channel. Such erosion is impossible to stop without taking serious measures. If I'm wrong about the genesis of this problem, perhaps you will point out the discrepancies. But it sure does look like a small part of some large issues I've dealt with. +oM

A photo would be helpful. If you have an effective groundcover, and around here there are a bunch of ferns that work well as groundcover, adding some new perennials, shrubs or small trees inset into the ferns to add interest might work better than changing out something that is working to control erosion along the water. Getting new plantings established on a slope can be difficult when one considers weed control and erosion during the time something is getting established, and many plants aren’t happy on a slope or won’t provide effective control for erosion and slippage. There are also rules that effect what you can do along public waterways because your erosion issues can effect water quality for everyone along the same waterway. So be sure to research how those laws effect what you can do since fines can be steep and you might be required to return everything to its prior condition. Or hire a designer who is well versed in the legal aspects of design along shorelines.