Description and flavor [edit]. The marionberry is a vigorously growing trailing vine, usually producing just a few canes up to 20 feet long. The vines have many large spines, and the fruiting laterals are long and strong, producing many berries.he marionberry's growing conditions are perfectly adapted to the mild, maritime Oregon climate, with its mild rains and warm summers. The berries ripen throughout late spring and early summer. The harvesting season is typically between July 10 and August 10, with a single acre producing up to six tons in a harvest.