Trichodesma africanum (L.) Sm.
Borago africana L.
Ara.: Alkah, al harricha, uochchem, himmin, lossiq, tada’at (last 3 in Egypt). Tamahaq: Halka, alqah, talkaït.
Annual or perennial plant, thermophyte, 20-80 cm, branched especially from the base, glabrous or pubescent, with rigid prickles, spaced apart. Stems rigid. Leaves opposite or partially alternate, very coarse, varied in size and shape, mostly lanceolate or oblong, usually tapered at both ends, petiolate; upper leaves sessile. Inflorescences terminal and axillary, narrowly paniculate; with lanceolate bracts; pedicels elongated and decumbent during fruiting, densely hispid with scattered whitish hairs. Flower with calyx 6 mm, densely hairy; during fruiting, calyx 10 mm or more, very expanded at the base, with acute triangular lobes, ovate, and veined at the base. Corolla 10-12 mm in diameter, blue-purplish, turning to yellowish-red near the corolla tube; tube yellow; lobes oval, long-attenuated. Anthers densely hairy, with glabrous edges. Nutlets brown, 4-5 mm, ovate, densely covered with uncinate hairs and temporarily surrounded by a dentate margin.
Flowering:
March to May.
Fruiting:
June and July.
Habitat:
Rocky desert areas.
Distribution:
Saharan-Arabian, Sudan, tropical Africa and South Africa, reaching North Africa in the central and southern Sahara and the Egyptian Mediterranean coast.
Observations:
In the Tibesti Massif T. africanum stems are only slightly woody, but can reach up to 2 m in height, causing Quézel to define it as T. giganteum (T. fruticosum Maire, T. giganteum Quézel), easily separated because the former species has the surface of the stems covered in an indumentum of applied and very short grey hairs, in addition to the characteristic upright hairs of both species.
In Tassili n’Ajjer (Algeria) T. gracile Batt. & Trab. (Tamahaq: Talkaht), has been described; it is an annual or perennial plant, with an indumentum of rigid hairs, like prickles. Leaves linear-lanceolate and variable: upper leaves alternate and sessile, and lower leaves from opposite to subopposite and petiolate. Flowers with pedicels 10-14 mm, filiform, hispid, curved. Calyx with a base from rounded to subtruncate, not gibbous, with hispid indumentum, with longly attenuated teeth 10 mm. Corolla blueish, with patent and attenuated lobes. Anthers with hispid dorsal side, apexes with long and twisted appendages. Nutlets oblong and appendages filiform. This is a very much argued taxon since many authors consider it a synonym of T. africana (e.g. Quézel, African Plant Database, POWO); instead Valdés (2011), in Euro+Med Plantbase, recognises it as a separate species. Battandier & Trabut indicate that it differs from T. africanum by its narrow leaves, larger flowers, sepals longly attenuated, sparse habit, and shorter, less rigid and tuberculated hairs.
Conservation status:
Fairly common species and widely distributed. Currently, they have not been assessed at a global level in the IUCN Red List of Threatened Species. In the Livre Rouge de la flore vasculaire du Maroc (Fennane, 2021) it has been considered as Least Concern (LC).