You don't need a concrete foundation for a small wall. You can make a dry stone wall. There are ones like this that last hundreds of years with the odd bit of maintenance. Even in areas where it the temperature ranges from -40 to +30 deg C a wall can be stable with some preparation:
- a two or three inch base of compacted stone dust
- some longer stones to act as "deadmen" to stabilize the wall (optional for short walls)
- four inch drain pipe with sleeve at the inside base of the wall to allow drainage
- a taper on the wall so it leans into the soil
- geotextile fabric to keep soil from washing out
See an example for more details here.