The Collaborative International Dictionary of English v.0.48:

Ragweed \Rag"weed`\ (r[a^]g"w[=e]d`), n. (Bot.)
   A common American composite weed (Ambrosia artemisiaefolia)
   with finely divided leaves; hogweed.
   [1913 Webster]

   Great ragweed, a coarse American herb (Ambrosia trifida),
      with rough three-lobed opposite leaves.
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The Collaborative International Dictionary of English v.0.48:

Wormwood \Worm"wood\, n. [AS. werm?d, akin to OHG. wermuota,
   wormuota, G. wermuth, wermut; of uncertain origin.]
   [1913 Webster]
   1. (Bot.) A composite plant (Artemisia Absinthium), having
      a bitter and slightly aromatic taste, formerly used as a
      tonic and a vermifuge, and to protect woolen garments from
      moths. It gives the peculiar flavor to the cordial called
      absinthe. The volatile oil is a narcotic poison. The term
      is often extended to other species of the same genus.
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   2. Anything very bitter or grievous; bitterness.
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            Lest there should be among you a root that beareth
            gall and wormwood.                    --Deut. xxix.
                                                  18.
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   Roman wormwood (Bot.), an American weed (Ambrosia
      artemisiaefolia); hogweed.

   Tree wormwood (Bot.), a species of Artemisia (probably
      Artemisia variabilis) with woody stems.

   Wormwood hare (Zool.), a variety of the common hare (Lepus
      timidus); -- so named from its color.
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The Collaborative International Dictionary of English v.0.48:

Bitterweed \Bit"ter*weed`\, n. (Bot.)
   A species of Ambrosia (Ambrosia artemisi[ae]folia); Roman
   worm wood. --Gray.
   [1913 Webster]