Aethusa cynapium L. Blekot pospolity – Fool’s parsley – is an annual plant from Apiaceae family. It grows to 10-50 cm of height. It has angular stem, branched in the upper part. Leaves are glabrous, their undersurface is shiny. The plant flowers from June to October. It is an insect-pollinating and self-pollinating plant. It grows on roadsides and crop fields. The plant is an indicator of limestone soils. Aethusa cynapium and its rhizomes contain toxic chemical compounds, coniine and cynapine, as well as formic acid and butyric acid. The plant is poisonous, in larger doses causes nervous system paralysis and irritation of mucous membranes.