The Collaborative International Dictionary of English v.0.48:

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 (Valeriana officinalis) has a strong smell, and is
   much used in medicine as an antispasmodic.
   [1913 Webster]

   Greek valerian (Bot.), a plant (Polemonium caeruleum)
      with blue or white flowers, and leaves resembling those of
      the officinal valerian.
      [1913 Webster]

WordNet (r) 3.0 (2006):

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