The Collaborative International Dictionary of English v.0.48:

Madder \Mad"der\ (m[a^]d"d[~e]r), n. [OE. mader, AS. maedere;
   akin to Icel. ma[eth]ra.] (Bot.)
   A plant of the genus Rubia (Rubia tinctorum). The root is
   much used in dyeing red, and formerly was used in medicine.
   It is cultivated in France and Holland. See Rubiaceous.
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   Note: Madder is sometimes used in forming pigments, as lakes,
         etc., which receive their names from their colors, such
         as madder yellow.
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   Field madder, an annual European weed (Sherardia
      arvensis) resembling madder.

   Indian madder, the East Indian Rubia cordifolia, used in
      the East for dyeing; -- called also munjeet.

   Wild madder, Rubia peregrina of Europe; also the Galium
      Mollugo, a kind of bedstraw.
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The Collaborative International Dictionary of English v.0.48:

Bedstraw \Bed"straw`\, n.
   1. Straw put into a bed. --Bacon.
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   2. (Bot.) A genus of slender herbs, usually with square
      stems, whorled leaves, and small white flowers.
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   Our Lady's bedstraw, which has yellow flowers, is Galium
      verum.

   White bedstraw is Galium mollugo.
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WordNet (r) 3.0 (2006):

Galium mollugo
    n 1: Eurasian herb with ample panicles of small white flowers;
         naturalized in North America [syn: wild madder, white
         madder, white bedstraw, infant's-breath, false baby's
         breath, Galium mollugo]