Here is a small article about Normandy hedgerows, including a typical cross-section;
http://www.lonesentry.com/normandy_lessons/index.html
Many hedgerows also had stone walls in the core instead of just earth. Farmers would remove rocks from their fields and stack them into walls at the edges of the fields. Over the centuries, these would end up covered in dirt with the hedges growing on top of them, or sometimes just bare stone walls to be used as fences.
Parsley, oregano, basil and other dried herbs work well for leaf litter. Birch tree catkins, shredded apart, also work well. Hairspray will work to hold it down, but I prefer to use diluted white glue in a spray bottle. The herbs tend to fade in color over time, so I tint the glue mix the appropriate shade to prevent the loss of color.