Literally, a weed is a wild plant growing where it is not wanted. I found this outcropping of mushrooms growing on my lawn under an old oak tree. They weren't there when I went to sleep but were when the sun came up. The largest living organism on earth was discovered in the Malheur National Forest in eastern Oregon. A fungus (mushroom) living three feet underground was estimated to cover 2,200 acres. After testing samples from various locations, scientists said it was all one organism. Officially known as Armillaria ostoyae, or the honey mushroom, the fungus is 3.5 miles across and takes up 1,665 football fields. The small mushrooms visible above ground are only the tip of the iceberg. Experts estimate that the giant mushroom is at least 2,400 years old, but could be 7,200 years old. That is one giant old weed!