In Cornwall, a “hedge” is a stone-faced earth bank, with or without vegetation. It is the bank itself that is referred to as the hedge rather than the plants, although many do have a low, dense row of shrubs, which may or may not be laid.
The base of the banks was sometimes formed from debris excavated from local tin mines. Making and repairing a Cornish hedge is a very particular craft, akin to building a dry stone wall, as it involves the assembling of the stones into a stable form.
The Cornish Hedges website has a huge amount of information on these hedges, their history and how to care for them: