The Collaborative International Dictionary of English v.0.48:

leadplant \leadplant\ n.
   A shrub (Amorpha canescens) of sandy woodlands and
   streambanks of the Western U. S. having hoary pinnate flowers
   and dull-colored racemose flowers; it is thought to indicate
   the presence of lead ore.

   Syn: lead plant, Amorpha canescens.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

leadplant
    n 1: shrub of sandy woodlands and stream banks of western United
         States having hoary pinnate flowers and dull-colored
         racemose flowers; thought to indicate the presence of lead
         ore [syn: leadplant, lead plant, Amorpha canescens]