verbena \verbe"na\, n. l. see vervain. bot.
   a genus of herbaceous plants of which several species are
   extensively cultivated for the great beauty of their flowers;
   vervain.
   1913 webster

   note: verbena, or vervain, was used by the greeks, the
         romans, and the druids, in their sacred rites.
         --brewer.
         1913 webster

   essence of verbena, oil of verbena, a perfume prepared
      from the lemon verbena; also, a similar perfume properly
      called grass oil. see grass oil, under grass.

   lemon verbena, or sweet verbena, a shrubby verbenaceous
      plant lippia citriodora, with narrow leaves which
      exhale a pleasant, lemonlike fragrance when crushed.
      1913 webster
see also:
vervain essence of verbena oil of verbena grass oil grass oil grass 
lemon verbena sweet verbena lippia citriodora