According to Wikipedia, the Boysenberry was developed by Rudolph Boysen.  He didn’t have a lot of success so the growing was ultimately taken over by George Darrow and Walter Knott.  They had a lot more success and after making and selling boysenberry preserves, it ultimately led to the founding of Knott’s Berry Farm.

 You don’t seem boysenberries grown commercially because the skin of the fruit is thin and doesn’t do well during bulk harvesting, processing and shipping. There were other issues too that made it a less-than-ideal candidate for commercial production.  It’s a shame because these are wonderful if you can find them.

 The original plants were said to be a cross between European raspberry, European blackberry, American dewberry, and loganberry.  Logan berries are a hybrid between a raspberry and a blackberry.  This plant has a very long pedigree.

 As with other berries, they are very healthy with a high dose of antioxidants as well as a delicious flavor.

 This is a plant worth growing if you can protect it from the deer and other animals that love to browse on the foliage.