This variety has a large number of names: it can be found also listed as Black Russian, Davis Purple, Eureka Purple, Fenton Blue, Purple Marker, Purple Mountain, Shaw #7, and Blue of Sweden. This may be an interesting debate: different names for the same cultivar originated because of marketing - but also - different names show a different history for cultivars grown in different regions of Russia or Skandinavia. Different soils in time have changed the genetics of the cultivars slightly ... the difference is so small that genetic fingerprinting is not yet able to tell the difference. BUT FYI AgriCanada the Canadian Agency similar to the USDA recommends to keep the cultivars separate with different names. I follow this advise and have a large catalog of blues. The same agency also reports that the Congo variety is believed to have been crossed in 1900. More information can be found by googling Kenosha Potato Project.
On Feb 24, 2005, tweezle from State College, PA (Zone 5b) wrote:
These medium size tubers are great for all kinds of cooking and baking with a really nice flavor. The potato is not as resistant to scab as others. To keep the blue color, add a tablespoon or two of vinegar to your cooking water. Makes a lovely patriotic looking salad when made with All Red and a regular white potato. The kids loved them!