One of the mysteries of the English language finally explained.
Definition of pipeweed in English:
pipeweed
noun
1Any of various plants having straight, slender, especially hollow or unbranched stems, especially field horsetail (Equisetum arvense), and (US) (more fully "Indian pipeweed") a North American desert plant having erect leafless stems which are swollen near the top, Eriogonum inflatum (family Polygonaceae).
2Pipe tobacco; (also) the prepared leaves of any plant used as a substance to be smoked in a pipe.
Origin
Early 18th century (in an earlier sense). From pipe + weed.