Of all the aggressively invasive exotic species on the West Coast, Himalayan blackberry, Rubus armeniacus, could be the nastiest! It seems to be impossible to kill. It forms dense thickets of wickedly thorny canes that develop roots where they touch the ground. Even if canes are cut to the ground, and the roots are pulled out, new plants regenerate quickly from remaining bits of roots.
Individual canes can grow more than twenty feet long in their first year! They may lay on the ground to creep under a thicket, or arch up and over other plants that are fifteen feet tall. These canes develop blooming and fruiting branches in their second year. By their third year, they are replaced by new canes. The palmately compound leaves are smaller for the fruiting second year canes.
Trusses of white or very pale pink flowers bloom late in spring. Dark purplish black berries that started ripening a few weeks ago are now being depleted. Some experts believe that Himalayan blackberries are bigger and sweeter than the fruit of most garden varieties. However, berries are only bigger among well cultivated canes; and keeping canes contained and pruned is not easy.