Shrub 0.5-1 m tall, densely and divaricately branched below, bushy, with branches erect to ascending, the whole plant (usually except stems) glabrous. Stems red-brown, compressed (sometimes shallowly 2-lined) and densely villous-tomentose or rarely sparsely puberulous to glabrous when young, soon terete, eventually glabrous; internodes shorter than leaves; cortex exfoliating in usually internodal sheets; bark dark red-brown, smooth. Leaves sessile; lamina 10-25 x 3-12 mm, narrowly elliptic or narrowly oblong to broadly triangular-lanceolate, concolorous or slightly paler beneath, chartaceous, not or slightly glaucous, glabrous, plane, spreading or somewhat deflexed; apex acute to subacute, margin entire, base cordate to rarely rounded and deeply amplexicaul; venation: 2(3) pairs of laterals curved-ascending from lower 0.25(-0. 35) of midrib, tertiary reticulation dense and manifest but not prominent; laminar glands pale, dense to rather sparse, unequal, prominent; intramarginal glands all black or a few pale, dense but sometimes irregular. Inflorescence c. 5-40-flowered from up to 3 nodes, without flowering branches from lower nodes, curved corymbiform and dense or rarely lax and rounded-pyramidal; pedicels 2.5-4 mm; bracteoles (and bracts at uppermost 2-3 nodes) narrowly triangular-lanceolate to linear, with rather sparse black-glandular cilia. Flowers c. 15-20 mm in diam.; buds narrowly ellipsoid, acute. Sepals 3.5-6 x 1-2 mm, subequal, free or to c. 0.15 united, lanceolate to narrowly oblong, acute to subacuminate, with sessile marginal glands or margin glandular-ciliate; veins 3, laterals branching; laminar glands pale, striiform to usually punctiform; marginal and inframarginal glands black, round- or flat-topped, immersed to sessile or on short (rarely long) cilia. Petals rather pale bright yellow, not tinged red, 10-12(-14) x 4-5 mm, c. 2.5 x sepals, oblong-oblanceolate, obliquely truncate to rounded, apiculus obsolete or absent; laminar glands pale, few, linear (rarely) or striiform to punctiform; marginal and inframarginal glands all black or some pale, not prominent. Stamens c. 25, longest 9-10 mm, c. 0.8-0.9 x petals; anther gland amber. Ovary 2-2.5 x 1-1.5 mm, narrowly ovoid; styles 6-7 mm, c. 3 x ovary, widely spreading-incurved. Capsule 4-5 x 2.5-3.5 mm, ovoid-ellipsoid, shorter than or equalling sepals, enclosed by petals twisting together. Seeds yellow-brown, c. 0.6 mm long; testa shallowly linear-foveolate.
2n= 18 (Larsen, 1962;Borgen, 1969; van Loon & de Jong, 1978, as var. lanuginosum; Reynaud, 1986).
Damp cliffs and walls, around springs and along rocky streams in open localities; 150-1600 m.
Canary Islands (all western islands, i.e. not Fuerteventura or Lanzarote).
H. reflexum is apparently not closely related to H. glandulosum, although the occurrence of intermediates (H. x joerstadii) suggests that they hybridise. The nature of these intermediates might be revealed by cytological investigation, as the species can have different chromosome numbers, viz. H. glandulosum 2n=40, 18, H. reflexum 2n=18. H. reflexum is variable, but there are no breaks in variation such as would warrant the recognition of plants with glabrous stems (var. leiocladum Bornm.) or short, ovate or ovate-elliptic leaves (var. myrtillifolium Bornm.) as distinct taxa.
H. reflexum is the basic species to which the H. montanum group is related. The chromosome numbers so far recorded for species in this group are all 2n=16 or 32.
 But see p. xxx
The younger Linnaeus's 'Habitat in Barrancas Americae' must be regarded as a lapsus calami.