Halimium (Dunal) Spach
Genus composed of some 13 species, distributed essentially through the Mediterranean region. In North Africa it is represented by some 8 species, all of Mediterranean distribution. For some authors, the differences with the genus Cistus are minimal and the species of this genus should be included under Cistus [e.g. Demoly (2006), ISFAN (2011)]. However, the traditional denomination will be maintained here, in agreement with other authors and The Plant List (accessed 27-10-2017).
Of the North African species 5 can be considered more or less shrubby, the other 3 woody species are usually subshrubs that barely exceed 0.5 m in height, they are:
H. calycinum (L.) K. Koch (H. commutatum Pau, Cistus calycinus L.), of linear leaves, 1-veined and with revolute margin, yellow petals (2n = 18); Iberian-Moroccan endemic, which in Morocco is abundant in the coastal and subcoastal dune systems of the NW, becoming rarer inland.
H. umbellatum (L.) Spach, with linear leaves, 1-veined and with revolute margin, white petals (2n = 18); of Mediterranean distribution, although it seems to be missing from the central Mediterranean. There are 2 subspecies: in North Africa subsp. viscosum (Willk.) O.Bolòs & Vigo is present, 25-70 cm, fairly viscous and with stellate hairs only on the underside of the leaves, with few or no stellate hairs on the upper side, pedicels and sepals. Subpecies of western Mediterranean distribution (Iberian-Maghrebi), in North Africa it is found through almost all of the Mediterranean area of Morocco and in the NW corner of Algeria (Tlemcen Mts.).
H. atlanticum Humbert & Maire is characterised by its very villous branchlets, with long hairs, calyx with 3 sepals and yellow petals. Species endemic to Morocco, only known from the Tazekka Massif (northern Middle Atlas) and Tidirhin Massif (central Rif).
All of the above are somewhat common species except for H. atlanticum which also has a very small distribution area. Currently, they have not been assessed at a global level in the IUCN Red List of Threatened Species. In Algeria H. umbellatum is included in the List of protected non cultivated flora (Executive Decree 12-03 on 4-Jan-2012).
Demoly, J.P. 2006. Notes taxonomiques, chorologiques et nouveautés nomenclaturales pour le genre Cistus L. élargi, incluant Halimium (Dunal) Spach (Cistaceae). Acta Bot. Gallica 153(3): 309-323.
Key to species
1 Leaves of sterile branches ± linear, with very revolute margin, 1-veined 2
1 Leaves of sterile branches not linear, ± broad and flat, with 3-5 veins 3
2 Flowers white, in inflorescences with umbeliform terminal verticil Halimum umbellatum
2 Flowers yellow, in inflorescences not umbelliform Halimium calycinum
3 Leaves of sterile branches densely tomentose, whitish and petiolate, leaves of fertile branches glabrescent, green and sessile Halimium ocymoides
3 All leaves ± equal in terms of tomentum and colour 4
4 Leaves and sepals with peltate hairs, mixed with stellate and glandular hairs 5
4 Leaves and sepals with irregularly branched hairs only 6
5 Leaves tomentose-whitish on both sides, velvety, with few peltate hairs. Calyx with 3 sepals Halimium atriplicifolium
5 Leaves tomentose-greenish, darker on upper side, with numerous peltate hairs. Calyx with 5 sepals (2 very small) Halimium halimifolium
6 Calyx with 3 sepals Halimium atlanticum
6 Calyx with 5 sepals 7
7 Shrub up to 2 m in height, with stellate hairs only on the upper sides of leaves. Flowers large (3.5-5 cm in diameter). In the region, only in the Rif Halimium lasianthum
7 Subshrub up to 0.80 m in height, with stellate hairs on both sides of leaves. Flowers smaller (2.5-3.5 cm in diameter). Endemic to the Anti-Atlas Halimium antiatlanticum
Updated by: F. Alcaraz & J. Charco.