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][1] 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][2].


  [1]: http://www.viralnova.com/stone-walls/
  [2]: http://gardening.stackexchange.com/a/5861/499