Question
I have a hillside that is quite steep.  It's about 70' long by 12' deep at the ends and
22' deep in the middle.  It slopes down in a CONVEX manner to a flat lawn.  I tore out some overgrown euonymus and had red clay brought in to reduce the very steep slope.  I
probably should have had more fill brought in but was trying to keep the cost as low as possible.  I have planted 30 small shrubs and 4 large flat rocks on the hillside and
bought 50 bales of pine needles to mulch the hillside.  We had moderately heavy rains last week and there was a fair amount of fine clay deposited at at the bottom of the hill.  Now I'm wondering if I need to put down a landscaping fabric to help stop clay erosion and
keep the pine needles from sliding down the slope (which I have not yet put down, by the way).  I've priced jute fabric and excelsior blanket (about the same) and wonder which would be best.  Also wondering if I chose the right mulch or would some other mulch be better on a steep slope and with red clay?  Have priced bagged mulch here, which would be easier getting up the slope to spread  and find cypress mulch to be the cheapest.  What do you think of it?  If cypress mulch stays in place better, how about putting down a thin layer of it and then putting down the pine needles, which I already have over the top of a thin layer of cypress mulch?  If it sounds like I've made a lot of decisions without doing my homework first, that's because I did.  Now I'm stuck with the red clay hillsie and need to do something to keep it in place.

Another question:  If I were to plant English ivy on the hill, my wife says this will choke out the shrubs I've planted.  Is this true?

"In researching erosion control on the net I've seen references to installing landscape fabric OVER the mulch.  What are the advantages and disadvantages of doing this?

I've mentioned jute and excelsior blankets as landscape fabrics.  Which do you think would be best on a red clay surface (I live in Hendersonville, NC) with pine straw mulch?  Would one or the other last longer, i.e. not degrade as quickly?"


Answer
Ok, lets address one by one:
1. Yes, landscape fabric will help in addition to mulch.
2. If your putting the fabric OVER the mulch then jute would be the only option. An Excelsior Blanket is really meant to replace mulch not cover it.
3. Pine straw is the best mulch for covering slopes in most cases as most people only put down a few inches and it will not float as easily as other mulches. If your slope is too steep no mulch will hold well in a strong rain unless there are other forces acting to hold it, like plants. The more mulch the better.
4. English ivy wont do well in full sun an dyes it will eventually become a maintenance problem as it tries to grow into your shrubs and trees. But this is true for any vine and English ivy is fairly slow compared to most others, pruning it several times a year is usually sufficient to keep it in check.
5. Installing jute over mulch helps it stay in place but is somewhat visible so it doesn't great. Typically only do this until your plants take hold and the jute deteriorates away to nothing.
6. Jute and excelsior blankets are not really the same although they are close. Excelsior is used as a barrier to cover seed or to restore banks without needing mulch, plants and seed are often planted by cutting through the mat or sprayed on the surface and then covered by the mat. The mat acts as a mulch and slows rain water and run off by its mass and thickness. Jute is typically just a grid of organic fabric that is used to hold mulch down most often and rarely used for much else. it is sometimes used as a weed barrier in fabrics with really tight weaves.
7. I do not know which would last longer. It would depend on many variables such as the location, weather, dampness, cuts made, installation, etc.

Best of Luck
Sean J Murphy, LA,ISA, LEED AP
Please check out my blogs and articles on landscape topics like this on my websites.
http://www.seanjmurphy.com
http://amenityarchitects.com