Cytisus arboreus (Desf.) DC.
Spartium arboreum Desf., Sarothamnus arboreus (Desf.) Webb
Eng.: Broom. Spa.: Escoba. Fre.: Cytise, genêt à balais. Ara./Tam.: Zauay.
Shrub up to 4 m in height —sometimes with a well defined trunk, ± tortuous—, unarmed, hermaphrodite, deciduous, highly branched from the base, with erect stems, with leaves promptly replaced. Stems and old branches with bark fissured longitudinally, glabrous, brownish. Young branchlets with (5)7-8 T-shaped ribs, densely sericeous at first, with straight hairs along the ribs and short crisped hairs along the intercostal valleys. Leaves all trifoliolate, without stipules, with petiole 3-17(30) mm, solitary on the macroblasts and in small groups on the brachyblasts, with leaflets 8-20 × 3-7 mm —in favourable conditions much larger—, subequal, obovate or oblong-obovate, glabrous on the upper side and sericeous or glabrescent on the underside, green. Flowers solitary or in groups of 2-6 on the branchlets of the current year, axillary, with pedicel 5-15 mm, slightly hairy, with 2-3 bracteoles on the upper half. Calyx 5-7 mm, campanulate, green at first and then a greyish-brown, bilabiate, the upper lip with 2 small teeth at the tip and the lower lip with 3, also very small, as long or slightly longer than the upper lip. Corolla 15-22 mm, papilionoid, yellow, with an ovate-suborbicular standard, emarginate or notched at the apex, glabrous, larger than the wings and the keel, the latter obtuse. Androecium monadelphous, with 10 stamens. Ovary glabrous or hairy, with style ± cylindrical throughout its length, and capitate stigma. Pod 30-45 × 7-8 mm, linear-oblong, highly compressed, green at first and then black, glabrous or hairy, with 4-12 seeds. Seeds 3-4 mm, ovoid, compressed, smooth, greenish-brown to brown.
Flowering:
February to May.
Fruiting:
May to July.
Habitat:
Forests, thickets and rocky areas, up to 1,800 m altitude, on siliceous or poorly calcified soils, sometimes on dolomites, in semiarid (in shady and damp areas) to humid bioclimate, on mesomediterranean and thermomediterranean floors.
Distribution:
SE France, Iberian Peninsula and NW Africa. In North Africa it grows almost throughout the entire Mediterranean non-steppic area of Morocco, reaching towards the S up to the western Anti-Atlas and the mountains of the western Sahara. Towards the E it reaches Algeria, where it is distributed throughout most of the western and central Tellian Atlas.
Observations:
Extremely polymorphic species, of which a good number of subspecies and varieties have been described, not always recognised by all authors. Plants with a glabrous ovary and pods are identified as C. arboreus subsp. catalaunicus
(Webb) Maire (Sarothamnus catalaunicus Webb), a subspecies present in the SE of France, NE of Spain and Andalusia; in the studied territory it is distributed along the NW Rif, Middle Atlas and High Atlas. Conversely, those plants with a hairy ovary and pods are grouped into 2 subspecies, which in turn are separated by the characteristics of the indumentum of the pod. Plants with densely hairy pods, with hairs of more than 2.5 mm, are included in C. arboreus subsp. baeticus (Webb) Maire [Sarothamnus baeticus Webb, C. baeticus var. macranthus Ball, C. arboreus subsp. macranthus (Ball) Maire], the most common taxon, present in almost all the African distribution area for the species (it also grows S and W of the Iberian Peninsula), from the Tellian Atlas to the western Anti-Atlas. Plants with pods covered in shorts and applied hairs, 0.3-2.5 mm, are included in C. arboreus subsp. arboreus (C. arboreus var. transiens Maire), a North African endemic which range extends across the eastern Rif, the Tellian Atlas and the mountains of western Sahara.
Conservation status:
A relatively common and widely distributed species, not considered threatened. In the IUCN Red List of Threatened Species, it is listed as Least Concern (LC) at global level.