Teucrium L.

Genus composed of about 280 species with an almost cosmopolitan distribution, but mainly in Mediterranean areas. In North Africa it is represented by about 75 species, distributed especially around the Mediterranean area and less dry areas of the Sahara. Most species are annual or perennial plants, or subshrubs to 0.5(1) m in height, some with a woody base but with herbaceous branches. Only 1 species, T. fruticans, can sometimes be considered as shrub, with woody stems and branches to 1.5(2) m in height. Other shrubby species smaller in size, but still considerable (in good conditions they can reach up to 1 m), are T. malenconianum, T. brevifolium and T. chardonianum.

Some species are small woody shrubs of no more than 40 cm in height: T. divaricatum Boiss., with leaves coriaceous and petiolate, ovate-cuneate, crenate or incised-crenate, flowers with purple corolla; it is typical of the eastern Mediterranean, and is found in North Africa in the E of Libya (Cyrenaica); T. compactum Lag., from the western Mediterranean, has leaves with cuneate base, crenate; it is found in the N of Algeria and Tunisia and in the NW of Libya; T. decaisnei C.Presl [T. pilosum (Decne) Asch. & Schweinf., T. sinaicum Boiss.] viscid small shrub, with inflorescences solitary or in groups of 2-3, in desert areas of E of Egypt, including the Sinai Peninsula and in Libya (Cyrenaica); and T. zanonii Pamp., subshrub, very rare, endemic to Libya (Cirenaica), densely velutinous-tomentose, prostrate branches, with verticillasters densely arranged in short terminal spikes, oblongish.

Amongst the not entirely herbaceous species, with woody main stems, the following are worth mentioning: T. barbarum Jahand. & Maire, subshrub with long and almost erect branches, up to 1 m in height, sometimes rupicolous subshrub, with leaves subentire or with irregularly crenate-lobulate margin, green on the upper side and grey on the underside; the leaves on flowering branches villous-tomentose on both sides, endemic to N Morocco (between the Rif, Middle Atlas and the Atlantic ocean); T. bracteatum Desf., very hispid subshrub, with lanceolate leaves, endemic to the northern area of Algeria and Morocco (western Rif); T. radicans Bonnet & Barratte, extremely rare subshrub, endemic to north Tunisia, very localised.

A further 3 species have stems and main branches hardened, ± lignified, but rarely woody, and up to 80 cm in height, widely distributed but not endemic in the Mediterranean region: T. flavum L., T. scorodonia L. and T. pseudo-scorodonia Desf. The first species has yellow flowers and calyx with 5 subequal teeth. The other 2 have greenish-yellow flowers and bilabiate calyx, with upper tooth much longer than the other. The latter 2 are differentiated primarily because T. scorodonia has a glabrescent calyx and T.pseudo-scorodonia has a villous calyx.

Usually common species, but sometimes very threatened, at least locally. Currently, they have not been assessed at a global level in the IUCN Red List of Threatened Species. In the Red List of vascular plants of Egypt (Flora Aegyptiaca Vol 1, 2000) T. decaisnei is listed as “Vulnerable”.

Updated by: B. Valdés & J. Charco.