Marionberries are a blackberry cultivar of the trailing cane variety, a cross between the Chehalem and Olallieberry lackberry . It was named after the county where it was developed in Marion, Oregon during the 1950's.
Marionberries have an intense blackberry flavor, they are plump, and juicy and have less seeds than their counterparts. They are supposed to freeze better than the other blackberries, in the sense that they will hold their shape after thawing. (I shall be able to confirm this outstanding marionberry property only after I have tried freezing and thawing them myself.)
What I can say for sure is that nothing beats them in smoothies, yogurts, pies and cheesecakes. Has anyone tried them brandied?