Those blackberries grew throughout my woods when I lived in WA State, where ever the sunlight could penetrate. My schnauzer used to eat them right off the vines. They were really good and always attracted a lot of pickers. We never tried to get rid of them because they grew on a part of the land that was devoted to hemlock and cedar trees, growing wild.
They are rather tasteless and the seeds are too large for jam or jelly compared to the small wild blackberry that also grows in the PNW where it hasn’t been pushed out by the Himalaya berry. I’ll bet you are sitting on some great gardening tidbits saving them for tomorrows thread...