We live in a forested area of Western Washington and have noticed fast-growing tree-like weeds popping up all over our land. So far they range in height from about 3 - 5 feet. Their 'trunks' range from 2 - 4 inches in diameter and are covered in thorns. Mature leaves are approximately 12 inches across and have an alternate arrangement. It appears that some maroon/purple flowers or berries are emerging. We have been unable to identify this plant through other resources. Thank you for your help!
Welcome to the forums! Looks like Oplopanax horridus syn Echinopanax horridus https://www.google.co.uk/search?q=O...PA7AbK5IGoAQ&ved=0CAgQ_AUoAQ&biw=1670&bih=764 http://en.wikipedia.org/wiki/Devil's_Club
You better keep off from it, or even clean it up. There is a reason for the "horribile" indeed it is a horrible plant. I fell in some and the thorns cause inflammation in the skin. Though has medical properties, I try not to contact with them, but we just have so many it spreads by the root and can be invasive.