Source : Webster's Revised Unabridged Dictionary (1913)

Valerian \Va*le"ri*an\, n. [LL. valeriana, perhaps from some
   person named Valerius, or fr. L. valere to be strong.
   powerful, on account of its medicinal virtues: cf. F.
   val['e]riane.] (Bot.)
   Any plant of the genus {Valeriana}. The root of the officinal
   valerian ({V. officinalis}) has a strong smell, and is much
   used in medicine as an antispasmodic.

   {Greek valerian} (Bot.), a plant ({Polemonium c[ae]ruleum})
      with blue or white flowers, and leaves resembling those of
      the officinal valerian.

Source : WordNet®

Greek valerian
     n 1: erect or spreading perennial of the eastern United States
          [syn: {Polemonium reptans}]
     2: pinnate-leaved European perennial having bright blue or
        white flowers [syn: {Jacob's ladder}, {charity}, {Polemonium
        caeruleum}, {Polemonium van-bruntiae}, {Polymonium
        caeruleum van-bruntiae}]