pissabed

Any dandelion (Taraxacum officinale), formerly much used for its diuretic properties.

Of flowers there was no trace, save of the flowers that plant themselves, or never die […] The chief of these was the pissabed.

The tufted hillock […] had no buildings on and only golden clumps of piss-the-bed that were not yet gone into misty balls of seed.

Any of various other wild plants with diuretic properties; bluet, oxeye daisy, etc.

A bedwetter.