noun
scouring rush; common horsetail; Equisetum hyemale
A perennial plant with jointed, hollow stems. Historically used for scouring and polishing due to its high silica content.
木賊は茎に節がある植物です。
The scouring rush is a plant with joints on its stems.
昔の人は木賊で木を磨いた。
People in the past polished wood with scouring rushes.
スギナ (field horsetail) is a related but different species; 木賊 refers specifically to the rough, evergreen variety used for scouring.
The kanji 木賊 literally means 'wood thief' or 'wood bandit', possibly referring to its rough texture that 'steals' the smoothness of wood. The reading とくさ is of uncertain origin.