The Collaborative International Dictionary of English v.0.48:

life-of-man \life-of-man\ n.
   An unarmed woody rhizomatous perennial plant (Aralia
   racemosa) distinguished from wild sarsaparilla by more
   aromatic roots and panicled umbels; it grows from
   Southeastern North America to Mexico.

   Syn: American spikenard, petty morel, Aralia racemosa.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

life-of-man
    n 1: unarmed woody rhizomatous perennial plant distinguished
         from wild sarsaparilla by more aromatic roots and panicled
         umbels; southeastern North America to Mexico [syn:
         American spikenard, petty morel, life-of-man, Aralia
         racemosa]