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Armillaria is a genus commonly known as the Honey mushroom, and sometimes called Shoestring Rot. The mycelium attacks the sapwood and is able to travel great distances under the bark or between trees in the form of black rhizomorphs ("shoestrings"). A number of species used to share the name Armillaria mellea.
Armillaria armillare
The honey mushroom Armillarea armillea can grow to tremendous proportions underground, stretching over a square kilometer and weighing 14 tons, killing trees all along its path, sending up its flower-like bunches of edible fungus in the wet fall season.
Armillaria mellea
Use this fungus with extreme caution since it kills trees and there is no known preventative 1)
mycorrhiza of Gastrodia elata 2)
This strain can be introduced onto a bed of Quercus wood for germination of Gastrodia elata seeds 3)
Armillaria ostoyae (Romagn.) Herink
Quite common on both hardwood and conifer wood in forests west of the Cascade crest. A mushroom of this type in the Malheur National Forest in the Strawberry Mountains of eastern Oregon, U.S. was found to be the largest fungal colony in the world, spanning 8.9 km² (2,200 acres) of area. This organism is estimated to be 2,400 years old. The fungus was written about in the April 2003 issue of the Canadian Journal of Forest Research. While an accurate estimate has not been made, the total mass of the colony may be as much as 605 tons. If this colony is considered a single organism, then it is the largest known organism in the world by area, and rivals the aspen grove "Pando" as the known organism with the highest living biomass.
In 1992, a relative of the Strawberry Mountains clone was discovered in southwest Washington state. It covers about 6 km² (1500 acres).
Another "humongous fungus" is a specimen of Armillaria bulbosa found at a site near Crystal Falls, Michigan covers 0.15 km² (37 acres), and was published in Nature 356:428-431.