Question
Tom:
I am in zone 8 (piedmont of South Carolina) and have an area along the lip of a ditch fronting my home (about 200 feet)that nothing other than weeds and vines seem to like.
Recently I have decided to try planting Liriope along a recessed shelf about 6 inches below the ditch top as a erosion plant and to spruce things up. Here's the problem...the soil is as hard as a rock. I have loosened a strip of soil and dug planting holes some 5 inches deep and the same width, sprinkled a few time released fertilizer pellets in each and added potting soil,but sooner or later the roots are going to hit that hard dirt. Do you think the plant roots will penetrate and these plants will survive and what have I done incorrectly.  

Answer
Hey Ben,
Thanx for your question.  I think that Liriope is a good choice for what you're attempting to do.  I think you would be surprised to know many roots of even the most basic plants can penetrate the hardest objects.  Have you ever seen Stone Mountain Georgia and some of the stuff growing out of nothing but rock?  Same thing out in the desert Southwest.  Trees, plants, cacti, growing out of seams in the rocks.  It sounds to me like you prepared some soil and it will be up to the plant to make it and liriope is a tough customer.  Keep it watered and fertilized its first year and I think you'll be successful.  I hope this helps.
Tom