760. RETAMA SPHAEROCARPA. James Cullen and Gwilym Lewis

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1 760. RETAMA SPHAEROCARPA Leguminosae James Cullen and Gwilym Lewis Summary. Retama sphaerocarpa (L.) Boiss., (Leguminosae) a yellow-flowered shrub from the Iberian Peninsula and North Africa, is described and illustrated. The genus Retama described by Rafinesque in 1838 is a conserved name over Lygos described by Adanson in The genus comprises four species (Charco, 2001; Polhill & Van Wyk, 2005) which have a geographical range from Macronesia and southern Europe to North Africa the Middle East, Saudi Arabia and the Yemen. The name Retama derives from the Arabic retem or retam for this broom-like genus of plants. The painting of Retama sphaerocarpa by Georita Harriott that accompanies this article is based on material cultivated in the Cambridge University Botanic Garden (CBG Accessions and ) that was originally acquired from the National Botanic Garden of Wales in 2001 and 2003, from material wild-collected by Ivor Stokes at Paco de Cuena above St. Raphael, near Almuñécar, east of Malaga in Spain. Until 2011 the identity of the cultivated specimens of this small-flowered leguminous shrub was unknown, but a dried specimen was finally matched against an herbarium specimen at the Royal Botanic Gardens, Kew. The main interest in this plant for gardens is its switch habit and the profusion of very bright yellow flowers displayed on numerous racemes which are borne at right angles to the supporting stems in spring and early summer. The hardiness of the species in the UK is doubtful (although it would probably survive in the gardens of coastal Cornwall and the Scilly Islands; in Cambridge it is grown in an unheated greenhouse and has yet to be tried outside). It is unlikely to become a popular garden plant because its habit is too untidy, but it will appeal to those with plenty of greenhouse space. The species is known by a large number of common names in the Iberian Peninsula; these are listed by Talavera (1999: 141). Curtis s Botanical Magazine 2013 vol. 30 (2): pp The Board of Trustees of the Royal Botanic Gardens, Kew

2 Retama sphaerocarpa (L.) Boiss., Voy. Bot. Espagne 2: 144 (1840). Spartium sphaerocarpum L., Mant. Pl.: 571 (1771). Type. Habitat in Europa Australi. (Herb. LINN). Lygos sphaerocarpa (L.) Heywood, in Feddes Repertorium 79: 53 (1968). Description. Sprawling shrub to small tree, 2 3 m tall, usually leafless when flowering; main stems pale brownish and lenticellate, sub-quadrangular, striate with 8 10 ribs (each rib shaped like an inverted V), 4 of which are more developed than the others, the ribs are seen especially on dried herbarium specimens (the stems essentially terete on fresh material), 4 5 ( 10) mm in diameter, often with many juvenile branches at the base, branching above into wide-spreading inflorescences (at least in cultivated material); younger stems striate with parallel green stripes, new growth bright green, densely greyish sericeous (giving the plant a silvery appearance from a distance) with very regularly arranged, parallel, very closely adpressed, simple, basifixed, white hairs (the occasional hair appears to be medifixed; this is unusual and not easytoseeevenwitha 10 lens); lateral shoots inserted more or less at right angles to the main shoots, except in the inflorescence, where they are more upright. Stem nodes have a single, brownish-tipped, persistent scale-like structure; true stipules are apparently absent, leaves simple, linear-lanceolate to with a slightly swollen central portion, but lanceolate, bright green, 6 11 ( 20) 1 2 mm, the apex acute, densely hairy when young becoming sparsely sericeous, falling early. Inflorescence a panicle of elongate racemes, the ultimate flowering branches are mostly at right angles to the shoots which bear them; the racemes are inserted singly or in pairs, each axillary raceme contains about (10 ) 15 20, laxly arranged (at least in cultivated material, although plants in the wild usually have fewer flowered racemes with more densely arranged flowers), ca 7 mm long pea flowers, bracts and bracteoles mm, elliptic, glabrous, falling early, pedicel short and relatively thick, ca mm long, sericeous, glabrescent. Flowers are usually somewhat deflexed and arched downwards (although some inflorescences bear fewer, more upright flowers with longer pedicels). Calyx obconical or subglobose and appearing slightly inflated, glabrous, bilabiate with two large acute upper and three smaller lower teeth, with a well developed hypanthium (receptacle) at the base, mm long to the tip of the upper teeth, the mouth of the calyx oblique so that the smaller lower teeth are extended further than the larger upper ones, the calyx usually falling after flowering, but leaving some remnant tissue at the base of the developing fruit. Corolla bright yellow, the standard petal ca 5 5 mm, equalling or slightly longer than the other petals in length, with a short mm long claw and a broadly ovate to orbicular blade, the sides of which are curved upwards, base rounded to somewhat truncate, apex rounded or emarginate, glabrous ; wing petals elliptic, glabrescent, with a basal ciliate auricle, a lateral pocket on the petal blade, and a 2 mm long claw, keel petals very slightly longer than the wings, elliptic, sparsely hairy on the upper third of the blade and along the lower margin, the basal auricle ciliate, the blade with a lateral pocket that fits into that on the wing petal, claw ca 2.5 mm long. Stamens 10, four shorter with basifixed anthers, five of medium length with dorsifixed anthers and one 96 The Board of Trustees of the Royal Botanic Gardens, Kew 2013.

3 Plate 760 Retama sphaerocarpa georita harriott

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5 Fig. 1. Retama sphaerocarpa. A, habit 0.1; B, flower 5; C, bud 7; D, standard petal 5; E, dissected flower to show staminal sheath and stigma 7; F, wing petals with ciliate auricle and lateral pocket 7. Drawn by Georita Harriott from material cultivated in the Cambridge University Botanic Garden (CBG accessions and ). larger stamen with a basifixed anther, the basifixed anthers ovoid, ca 0.5 mm long, dorsifixed anthers globose, ca 0.3 mm long, the stamen filaments united along their lower quarter into a U-shaped channel. Ovary green, bulbous, glabrous, 4 ( 6) ovulate, tapering into a paler green style which has a slightly hairy apical stigma. Fruits mm, ovoid to somewhat boat-shaped, slightly woody, brown with a rugulose surface, the pericarp dry and somewhat The Board of Trustees of the Royal Botanic Gardens, Kew

6 spongy at maturity, shortly apiculate, indehiscent or tardily dehiscent along one suture, persisting on the plant after maturity, usually 1 (to rarely 2)-seeded. Seeds dark brown, mm (Fig. 1). Distribution. Frequent across most of the Iberian Peninsula (Spain, Portugal), and also known from NW Africa (Morocco, Algeria, Tunisia). Habitat. Semiarid areas, especially on sandy soils, from coast to inland hills, and in subhumid areas, in oak forest (or secondary scrub derived from it), on slate, clay or chalky soils, or on limestone, rarely on granite, m. The species tolerates a wide range of environmental conditions and is rather indifferent to the type of substrate on which it grows. It is highly resistant to the continental Mediterranean climate and is sometimes abundant in deforested areas. Flowering time. March to May in the Iberian Peninsula, April to June in NW Africa. In North Africa fruiting from July to September. Conservation status. The species is common in the wild across a wide geographical area and is apparently under no threat. A conservation assessment of Least Concern (LC) is appropriate. Acknowledgements. Thanks to Georita Harriott who prepared the black and white line drawing and the colour plate that accompany this article; to Nicholas Hind who helped identify the Cambridge specimens, and to Lourdes Rico who assisted with the translation of habitat notes into English. REFERENCES Blamey, M. & Grey-Wilson, C. (1993). Lygos sphaerocarpa (Retama sphaerocarpa). In: Mediterranean Wild Flowers. Harper Collins, London. p. 84. Charco, J. (2001). Retama sphaerocarpa. In:Guía de los Árboles y Arbustos del Norte de África. Agencia Española de Cooperación Internacional, Madrid. p Heywood, V.H. (1986). Lygos Adanson (Retama Boiss.). In: Tutin, T.G., Heywood, V.H., Burges, N.A., Moore, D.M., Valentine, D.H., Walters, S.M. & Webb, D.A. (eds). Flora Europaea, Vol. 2: Rosaceae to Umbelliferae. Cambridge University Press. p Polhill, R.M. & Van Wyk, B.-E. (2005). Tribe Genisteae. In: Lewis, G., Schrire, B., Mackinder, B. & Lock, M. (eds). Legumes of the World. Royal Botanic Gardens, Kew. pp Talavera, S. (1999). Retama Raf. In: Talavera, S., Aedo, C., Castroviejo, S., Romero Zarco, C., Sáez, L., Salgueiro, F.J. & Velayos, M. (eds). Flora Iberica, Plantas vasculares de la Península Ibérica e Islas Baleares, Vol. VII. pp Madrid. 100 The Board of Trustees of the Royal Botanic Gardens, Kew 2013.