Mike, this is a project which requires a bit of logistical planning as you intend to hybridize which means the need for easy, close up access to your plants as you perform minute, hands on work. The simple answer to your question is...yes, any disturbed slope, no matter how slight, will erode. And, yes it is necessary to create barriers and layers edging the outside of each bed dug into a hill with rocks, lengths of board found on construction sites, brick...whatever material is available. In a situation such as yours I would include several sections of concrete blocks as edging set with the holes topside, holes filled with soil and planted with smaller growing herbs/flowers that attract beneficial insects which will help to control insect problems. All sorts of information can be found on the web re this subject. As I visualize your project and planting list the logistical part of your endeavor is what to plant where? Some need upright support, others sprawl. If the slope is large enough you might want to consider staggering the beds on the hill rather than one row after another marching up the hill. This would give room for access, growth and make necessary annual plant rotation easier.

If you have the time to look at my pics, please let me know if you think my theory as to source is correct. I know other side of roof arch is a problem as previous owners had put in huge landscaping rocks to prevent further erosion on that side of the yard (and it appears to be working). If you can think of anything specific please let me know. What I don't understand is why I went 3 years without any problems and then suddenly this started last fall. Just finished school and have big tuition payments so have to do any fixes myself. ..Thanks, Fletch Link 1 shows canal along my steps and at top of steps to the left you can see my hollow sidewalk someone had added on. http://n4szo.servebbs.net/myhouse/CIMG1674.JPG Link 2 Shows erosion along the steps. It actually looked much worse but I have been filling in with rocks and recovering some of the top soil from the lower sidewalk. http://n4szo.servebbs.net/myhouse/CIMG1676.JPG Link 3 shows top of stairs where hollow sidewalk connects. First signs started on left side where you can see my repair. Repaired worked for the most part but then water then redirected to the right where you can see my temp repair. Once I discovered sidewalk was hollow, I started filling in with rocks...probably 1 full bag (lowes) is now inside sidewalk. Only problem is until source is cut off, flow will continue to move to the left and whole thing starts over again. http://n4szo.servebbs.net/myhouse/CIMG1677.JPG Link 4 shows one source of the problem and where I originally thought was the sole source. Back in early fall, I noticed this small bare spot had a tiny hole pointing towards sidewalk. At first I thought it was caused by a mole or something. I have stuck plenty of rocks inside to attempt to plug it up. After awhile, I noticed a hole appearing behind it towards the shrubs and staircase (rear part of pic). That is when I realized this area was probably not the source of the problem (but certainly part of it). http://n4szo.servebbs.net/myhouse/CIMG1678.JPG Link 5 shows a wider view- I recently found signs of erosion to right of sign along the stair case. I also found previous attempts to address (some rocks) but I don't think they went far enough. Run off from roof lands in these shrubs and I think it has been digging holes and just generally running under this staircase and coming out on other side where you see my rocks. Thursday, I put out more rocks along with spare landscaping bricks to block off area around staircase. Water can still get under there, but it's flow rate should be much less now. Still may put in a bag of marble rocks just for extra protection. http://n4szo.servebbs.net/myhouse/CIMG1684.JPG Link 6 shows source of run off (wish I had a shot showing how steep roof is but you get the idea). Water lands in area between front porch and staircase. http://n4szo.servebbs.net/myhouse/CIMG1686.JPG Hopefully this gives you an idea of what I am seeing. Now off to Lowes to buy some top soil.

You have not said how steep your hill is. You can have very steep hills that do not erode without adding man made structures. The key is to keep every inch of the ground well covered with plants. Usually you will only see bare erosion spots if water is rushing down a specific point. You mentioned the down spouts, but it is not likely that they would cause the whole hill to erode. You might think about grading the flat back yard a bit so that all the water flows down to one point. Then at this one point, create a rock slide using larger rocks so that the water does not move the rocks. In effect you create a water fall but add enough large rocks so that it prevents erosion. the rocks don't have to be too big, just big enough and irregular enough so that they are stable. I have a slope on my property that is very steep - probably drops 10 ft for every 5 ft. It is made up of rock and soil covered with grass/weeds/golden rod. No errosion at all.

My vegies are on a 45degree slope. When my house was put in the leach field was put in about 8 to 10 feet below and the fill was just as it was dozed and fell to the lower level. Last year I decided I wanted a few Toms and Peppers 18 each LOL but nowheres to put them where they would get much sun except the hillside. My answer lottsa stones from an old wall. Carry up the hill and terrace then fill in it gave me 2 to 4 feet by 60. This year its harder the carry is getting longer on my 2nd tier. Now I have to wheel the fill down the hill to the leach field shovel into 5 gallon buckets climb up on the 1st tier dump ugh. I have room for 4 or 5 tiers but at least by next year I should be able to put a temp ramp from the side hill and eliminate the shovel bucket routine. You got good answers from the others for the easiest fixes but this post is just to show no slope is to steep. Regards Scott