humungous fungus

[Aruncus]

Looking in the new editon of Introductory Mycology by Alexopoulos et.
al... he cites some papers  discussing the humongous fungus.  These are :

Braxier, C.  1992.  A Champion Thallus.  Nature  356:38-383

Gould, S.J.   A Humongous Fungus Among Us.  Nat. Hist.  101: 10-19

Smith, M.L., J.N. Bruhn,  and J.A. Anderson.  1992.  The Fungus Armillaria
bulbosa Is Among the Largest and Oldest Living Organisms.  Nature 
356:428-31
 

Have Fun... this could lead you to other sources hopefully.  I live in
Washington state and we have the largest :)   Armillaria Ostoyae   Your
species of concern is actually, A. gallica according to the text
authors... bye