Giant Horsetail, Equisetum talmatiea
Seen at Hamby Park in Hillsboro, Oregon. The 5 stocks to the left are the spore-bearing fertile stems. The other plants are green photosynthetic sterile stems.
The Oregon Department of Agriculture considers this a noxious weed. It proliferates in wet areas and can quickly reproduce from spores and rhizomes. The plants are poisonous to animals that might eat them. Yet, parts of the plants can be eaten by humans. But, like mushrooms, you better know what you are doing.