Cistus × Laxus

''Cistus'' (from the Greek ''kistos'') is a genus of flowering plants in the rockrose family Cistaceae, containing about 20 species (Ellul ''et al.'' 2002). They are perennial shrubs found on dry or rocky soils throughout the Mediterranean region, from Morocco and Portugal through to the Middle East, and also on the Canary Islands.

''Cistus'', with its many hybrids and cultivars, is commonly encountered as a garden flower.

The common name rockrose (rock rose in the UK) is applied to the species, a name also shared by the related genera ''Halimium'', '' Helianthemum'' and ''Tuberaria'', all in the family Cistaceae. The common name ''gum cistus'' is applied to resin-bearing species, especially ''C. ladanifer''.

Description

The leaves are evergreen, opposite, simple, usually slightly rough-surfaced, 2–8 cm long. In a few species (notably ''C. ladanifer''), the leaves are coated with a highly aromatic resin called labdanum.

They have showy 5-petaled flowers ranging from white to purple and dark pink, in a few species with a conspicuous dark red spot at the base of each petal.

Taxonomy

Phylogeny

''Cistus'' and ''Halimium'' form a cohesive and the most derived clade within Cistaceae. Molecular phylogenetic analyses conducted between 2005 and 2011 confirm that ''Cistus'' species divide into two well-defined clades, neither of which was fully resolved internally. The first clade consists of those with purple and pink flowers (the "purple pink clade" or PPC). The second clade consists of those with white flowers or, in the case of ''Cistus parviflorus'', pale pink flowers (the "white or whitish pink clade" or WWPC). Although the flower colour of ''C. parviflorus'' is anomalous, it has very short styles, otherwise characteristic of WWPC species. A hybrid origin has been suggested. A simplified cladogram is shown below:

Within the purple pink clade (PPC), ''C. crispus'' is consistently the first diverging species. ''C. albidus'', ''C. creticus'' and ''C. heterophyllus'' form a well supported clade. Seven species endemic to the Canary Islands form a polytomy, resolved differently in different analyses, in which subtaxa of some species do not always cluster together. Within the white and whitish pink clade (WWPC), there is weak support for a clade consisting of ''C. clusii'' and ''C. munbyi''; the other species either formed part of a polytomy or resolved differently in different analyses. ''Halimium'' and ''Cistus'' were regularly shown to be paraphyletic with respect to one another.

Species

The following species are recognised in the genus ''Cistus'':

*'' Cistus albidus'' L.
*'' Cistus asper'' Demoly & R.Mesa
*'' Cistus atlanticus'' (Humbert & Maire) Demoly
*'' Cistus atriplicifolius'' Lam.
*'' Cistus calycinus'' L.
*'' Cistus chinamadensis'' Bañares & P.Romero
*'' Cistus clusii'' Dunal
*''Cistus creticus'' L.
*''Cistus crispus'' L.
*'' Cistus formosus'' Curtis
*''Cistus grancanariae'' Marrero Rodr., R.S.Almeida & C.Ríos
*''Cistus halimifolius'' L.
*''Cistus heterophyllus'' Desf.
*''Cistus horrens'' Demoly
*''Cistus inflatus'' Pourr. ex J.-P.Demoly, syn. ''Cistus psilosepalus'' Sweet
*''Cistus ladanifer'' L., including ''Cistus palhinhae'' N.D.Ingram – Gum Rockrose
*''Cistus lasianthus'' Lam.
*''Cistus lasiocalycinus'' (Boiss. & Reut.) Byng & Christenh.
*''Cistus laurifolius'' L.
*'' Cistus libanotis'' L.
*'' Cistus macrocalycinus'' (Pau) Byng & Christenh.
*'' Cistus monspeliensis'' L. – Montpellier Cistus
*''Cistus munbyi'' Pomel
*''Cistus ocreatus'' C.Sm.
*'' Cistus ocymoides'' Lam.
*''Cistus osbeckiifolius'' Webb
*'' Cistus palhinhae'' N.D.Ingram
*''Cistus palmensis'' Bañares & Demoly
*''Cistus parviflorus'' Lam.
*''Cistus populifolius'' L.
*'' Cistus pouzolzii'' Delile ex Gren. & Godr.
*''Cistus salviifolius'' L. – Salvia Cistus
*''Cistus sintenisii'' Litard. (syn. ''C. albanicus'')
*''Cistus symphytifolius'' Lam.
*'' Cistus tauricus'' C.Presl
*'' Cistus umbellatus'' L.

Gallery

Image:Cistus albidus(estepa blanca).jpg, ''Cistus albidus'' photo taken near Sitges
Image:Cistus May 2014-11.jpg, ''Cistus crispus''
Image:Cistus_heterophyllus.jpg, ''Cistus heterophyllus'' subsp. ''carthaginensis''. Critically endangered cistus from Cartagena (Spain).
Image: Cistus libanotis.JPG, ''Cistus libanotis'' Photo taken near Cádiz.
Image:Cistus salviifolius (plant).jpg, ''Cistus salviifolius''

Hybrids

In addition a large number of hybrids have been recorded, including:

* ''Cistus'' × ''aguilari'' O.E.Warb. ('' C. ladanifer'' × '' C. populifolius'')
* ''Cistus'' × ''akamantis'' Demoly
* ''Cistus'' × ''albereensis'' Gaut. ex Rouy & Fouc.
* ''Cistus'' × ''banaresii'' Demoly
* ''Cistus'' × ''canescens'' Sweet
* ''Cistus'' × ''cebennensis'' Aubin & J.Prudhomme
* ''Cistus'' × ''cheiranthoides'' Lam.
* ''Cistus'' × ''clausonii'' Font Quer & Maire
* ''Cistus'' × ''conradiae'' Demoly
* ''Cistus'' × ''corbariensis'' Pourr. ('' C. populifolius'' × '' C. salviifolius'')
* ''Cistus'' × ''cyprius'' Lam. ('' C. ladanifer'' × '' C. laurifolius'')
* ''Cistus'' × ''dansereaui'' P.Silva ('' C. ladanifer'' × '' C. inflatus'')
* ''Cistus'' × ''escartianus'' Demoly
* ''Cistus'' × ''florentinus'' Lam. ('' C. monspeliensis'' × '' C. salviifolius'')
* ''Cistus'' × ''hybridus'' Pourr.
* ''Cistus'' × ''incanus'' L. ('' C. albidus'' × '' C. crispus'')
* ''Cistus'' × ''ingwersenii'' Demoly
* ''Cistus'' × ''laxus'' Aiton ('' C. populifolius'' × '' C. inflatus'' ?)
* ''Cistus'' × ''ledon'' Lam. ('' C. laurifolius'' × '' C. monspeliensis'')
* ''Cistus'' × ''matritensis'' Carazo Roman & Jiménez Alb.
* ''Cistus'' × ''nigricans'' Pourr. ('' C. populifolius'' × '' C. monspeliensis'')
* ''Cistus'' × ''novus'' Rouy
* ''Cistus'' × ''obtusifolius'' Sweet ('' C. inflatus'' × '' C. salviifolius'')
* ''Cistus'' × ''pauranthus'' Demoly ('' C. parviflorus'' × '' C. salviifolius'')
* ''Cistus'' × ''philothei'' Sennen & Mauricio
* ''Cistus'' × ''platysepalus'' Sweet ('' C. monspeliensis'' × '' C. inflatus'')
* ''Cistus'' × ''pourretii'' Rouy & Foucaud
* ''Cistus'' × ''purpureus'' Lam. ('' C. ladanifer'' × '' C. creticus'')
* ''Cistus'' × ''rodiaei'' Verg. ('' C. ladanifer'' × '' C. albidus'')
* ''Cistus'' × ''santae'' (Sauvage) Demoly
* ''Cistus'' × ''skanbergii'' Lojac. ('' C. parviflorus'' × '' C. monspeliensis'')
* ''Cistus'' × ''stenophyllus'' Link ('' C. ladanifer'' × '' C. monspeliensis'')
* ''Cistus'' × ''timbalii'' Demoly
* ''Cistus'' × ''verguinii'' Coste ('' C. ladanifer'' × '' C. salviifolius'')
* ''Cistus'' × ''vinyalsii'' Sennen

Ecology

They are thermophilous plants, which require open, sunny places. This plant genus is peculiar in that it has developed a range of specific adaptations to resist summer drought and frequent disturbance events, such as fire and grazing. In addition, it can form both ectomycorrhizas and arbuscular mycorrhizas. More than 200 ectomycorrhiza-forming fungal species belonging to 40 genera have been reported so far to be associated with ''Cistus''. As with many other Cistaceae, the species of ''Cistus'' have the ability to form mycorrhizal associations with truffles (''Tuber'') and are thus able to thrive on poor sandy soils or rocks. ''Cistus ladanifer'' has been found to have mycorrhizal associations with '' Boletus edulis'', ''Boletus rhodoxanthus'', and '' Laccaria laccata''.

''Cistus'' are the only host of '' Cytinus hypocistis'', a small parasitic plant that lives on the roots and is noticeable only for a short period of time when in flower. The presence of the parasite does not seem to harm the host population.

''Cistus'' species are used as food plants by the larvae of some Lepidoptera species including '' Coleophora confluella'' and '' Coleophora helianthemella'', the latter recorded on ''Cistus monspeliensis''.

Various ''Cistus'' species are known to emit volatile oils, rendering the plants flammable.

Cultivation

Cistuses are suitable for sunny gardens with a nearly frost-free Mediterranean climate. The hardiest of the species is ''C. laurifolius'', which survived the hard frost at Royal Botanical Gardens at Kew in 1895 that eliminated all the cistuses save this and two white-flowered natural hybrids, ''C.'' × ''corbariensis'', already grown by John Tradescant the Elder, and ''C.'' × ''loretii'', a 19th-century introduction.

Cultivars

Cultivars (those marked have gained the Royal Horticultural Society's Award of Garden Merit) include:

*''C.'' × ''aguilarii'' 'Maculatus'
*''C.'' × ''argenteus'' 'Peggy Sammons' - pink flowers, grey-green leaves
*''C''. × ''bornetianus'' ‘Jester’
*''C.'' × ''cyprius''
*''C.'' × ''cyprius'' var. ''ellipticus'' 'Elma'
*''C.'' × ''dansereaui'' 'Decumbens'
*''C.'' × ''dansereaui'' 'Jenkyn Place'
*''C.'' × ''florentinus'' - white flowers
*''C.'' ’Gordon Cooper’
*''C.'' × ''hybridus'' - pink buds, white flowers
*''C''. × ''laxus'' ‘Snow White’
*''C.'' × ''lenis'' 'Grayswood Pink'
*''C''. × ''obtusifolius'' ‘Thrive’
*C.'' 'Paladin' - large white flowers, dark green leaves
*''C.'' × ''pulverulentus'' 'Sunset'
* ''C''. × ''purpureus'' - pink petals with dark blotches near centre
*''C.'' × ''skanbergii'' - small pink flowers
*''C.'' 'Snow Fire'
* ×''Halimiocistus'' 'Ingwersenii'
*×''Halimiocistus sahucii''

Gallery

File:Cistus ladanifer hybride.JPG, ''Cistus'' × ''dansereaui''
File:Cistus-hybridus.jpg, ''Cistus'' × ''hybridus''
File:Cistus purpureus.jpg, ''Cistus'' × ''purpureus''
File:Cistus skanbergii + Cistus verguinii-Clapiers-4144~2015 05 03.JPG, ''Cistus'' × ''skanbergii'' (pale pink) and ''Cistus'' × ''verguinii'' (white and spotted)

References

Bibliography

* Proposes merging ''Cistus'' and ''Halimium''.
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External links

{{Taxonbar, from=Q206127

Malvales genera
Taxa named by Carl Linnaeus