The Collaborative International Dictionary of English v.0.48:

Smartweed \Smart"weed`\, n. (Bot.)
   An acrid plant of the genus Polygonum (Polygonum
   Hydropiper), which produces smarting if applied where the
   skin is tender.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Hydropiper \Hy"dro*pi`per\, n. [NL., fr. Gr. "y`dwr water + L.
   piper a pepper.] (Bot.)
   A species (Polygonum Hydropiper) of knotweed with acrid
   foliage; water pepper; smartweed.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Lakeweed \Lake"weed`\, n. (Bot.)
   The water pepper (Polygonum Hydropiper), an aquatic plant
   of Europe and North America.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Culrage \Cul"rage\ (k?l"r?j), n. [OE. culrage, culrache; prob.
   fr. F. cul the buttok + F. & E. rage; F. curage.] (Bot.)
   Smartweed (Polygonum Hydropiper).
   [1913 Webster]