Tordylium maximum, known as hartwort, is an annual or biennial flowering plant in the carrot family (Apiaceae).

[2] Tordylium maximum is a hairy or bristly biennial or annual, growing to about 30–130 cm (1.0–4.3 ft) tall, with a hollow ridged stem that is usually branched.

The lower leaves are pinnate, with two to five pairs of coarsely toothed leaflets.

[3][2] Tordylium maximum was first described by Carl Linnaeus in 1753 in Species Plantarum.

[3] It has been found in south-east England, but only in one location in south Essex since 1875.