Literature: Brullo & de Marco (2000), Brullo & al. (2004)
Dittrichia, as currently understood (see Brullo & de Marco 2000), is a small genus of five species (only two according to most other authors), all native in the Mediterranean region.
Dittrichia was traditionally placed within Inula (and still is by some authors, see for instance Akeroyd & al. 2000). It is distinguished by cylindrical achenes that are abruptly contracted below pappus and pappus hairs that are basally connate. It is furthermore closely related to Pulicaria.
All species are densely glandular and have a very distinctive camphorous or resinous smell.
1. Annual plant, usually ca. 20-50 cm tall. Ligules 3,5-4 mm long, not or scarcely exceeding involucre. Leaves usually entire, up to 8(-13) mm wide === 1. Dittrichia graveolens
1. Perennial plant, usually ca. 40-130 cm tall. Ligules 8-12 mm long, distinctly exceeding involucre. Leaves usually coarsely dentate, up to 30 mm wide === 2. D. viscosa
Brullo S. & de Marco G. (2000) Taxonomical revision of the genus Dittrichia (Asteraceae). Portugaliae Acta Biol. 19: 341-354.
Brullo S., Campo G., Colombo P., Salmeri C. & Venora G. (2004) Morfologia, cariologia e anatomia fogliare nel genere Dittrichia Greuter (Asteraceae). Inform. Bot. Ital. 36: 489-496.