Helianthemum


Helianthemum, known as rock rose, sunrose, rushrose, or frostweed, is a genus of about 110 species of flowering plants in the family Cistaceae. They are widely distributed throughout the Northern Hemisphere, especially in the Mediterranean.
New World species formerly classified as Helianthemum have been transferred to genus Crocanthemum.

Description

These are usually shrubs or subshrubs, and some are herbaceous
annuals or perennials. The leaves are oppositely arranged, but some plants may have alternately arranged leaves along the upper stems. The flowers are solitary or borne in an array of inflorescence types, such as panicles, racemes, or headlike clusters. The flower has three inner sepals and two smaller outer sepals. It has five petals usually in shades of yellow, orange, or pink. The style at the center is tipped with a large stigma. The fruit is a capsule containing many seeds.

Ecology

Helianthemum are known to form symbioses with mycorrhizal fungi. In the Mediterranean they are associated with Terfeziaceae, the desert truffles. Together, plant and fungus may have a beneficial effect on the arid local landscapes, preventing soil erosion and desertification. Some symbiotic pairs include Helianthemum salicifolium and the truffle Tirmania nivea, and H. guttatum and T. pinoyi.
One of the most commonly observed mycorrhizae on Helianthemum is a member of a different family, Cenococcum geophilum. This fungus is not host-specific, and it often associates with oaks, as well. Some studies suggest that Helianthemum and oaks growing together in a habitat may "share" their mycorrhizae.
Helianthemum are food plants for the larvae of some Lepidoptera species, such as the large grizzled skipper and the silver-studded blue. The leaf miners Bucculatrix helianthemi and B. regaella both feed exclusively on Helianthemum sessiliflorum, as does Coleophora eupreta. C. ochrea is limited to Helianthemum, and C. bilineella and C. potentillae have been observed on the genus.

Cultivation

Several Helianthemum species, and the numerous hybrids and cultivars derived from them, are widely grown as ornamental plants, popular in rockeries. A broader range of colours is available among the cultivars, including bright salmon-pink to dark red. They are best grown in well-draining soil in full sun, and have a long flowering period from spring to summer. Numerous cultivars have gained the Royal Horticultural Society's Award of Garden Merit:
  • 'Amy Baring'
  • 'Fire Dragon'
  • 'Henfield Brilliant'
  • 'Jubilee'
  • 'Mrs C.W. Earle'
  • 'Rhodanthe Carneum'
  • 'The Bride'
  • 'Wisley Primrose'

    Species

112 species are accepted.
  • Helianthemum abelardoi
  • Helianthemum aegyptiacum
  • Helianthemum aganae
  • Helianthemum aguloi
  • Helianthemum almeriense
  • Helianthemum alypoides
  • Helianthemum angustatum
  • Helianthemum antitauricum
  • Helianthemum apenninum - white rockrose
  • Helianthemum × asperilanceolatum
  • Helianthemum asperum
  • Helianthemum assadii
  • Helianthemum baschkirorum
  • Helianthemum bilyanense
  • Helianthemum bramwelliorum
  • Helianthemum broussonetii
  • Helianthemum buschii
  • Helianthemum bystropogophyllum
  • Helianthemum canariense
  • Helianthemum canum
  • Helianthemum capralense
  • Helianthemum caput-felis
  • Helianthemum × carmen-joanae
  • Helianthemum × carolipaui
  • Helianthemum cinereoflavescens
  • Helianthemum cinereum
  • Helianthemum cirae
  • Helianthemum ciscaucasicum
  • Helianthemum citrinum
  • Helianthemum × conchitae
  • Helianthemum concolor
  • Helianthemum confertum
  • Helianthemum × coronadoi
  • Helianthemum coulteri
  • Helianthemum crassifolium
  • Helianthemum × crespoi
  • Helianthemum croceum
  • Helianthemum cylindrifolium
  • Helianthemum dagestanicum
  • Helianthemum dianicum
  • Helianthemum × digeneum
  • Helianthemum × doumerguei
  • Helianthemum edetanum
  • Helianthemum ellipticum
  • Helianthemum eriocephalum
  • Helianthemum × fabadoi
  • Helianthemum × finestratense
  • Helianthemum fontanesii
  • Helianthemum geniorum
  • Helianthemum germanicopolitanum
  • Helianthemum getulum
  • Helianthemum glaucescens
  • Helianthemum gonzalezferreri
  • Helianthemum gorgoneum
  • Helianthemum grosii
  • Helianthemum guerrae
  • Helianthemum × guiraoi
  • Helianthemum hadedense
  • Helianthemum × heerii
  • Helianthemum henriquezii
  • Helianthemum hirtum
  • Helianthemum × hispidum
  • Helianthemum hymettium
  • Helianthemum inaguae
  • Helianthemum juliae
  • Helianthemum kahiricum
  • Helianthemum kotschyanum
  • Helianthemum × lagunae
  • Helianthemum ledifolium
  • Helianthemum leptophyllum
  • Helianthemum linii
  • Helianthemum lippii
  • Helianthemum × lucentinum
  • Helianthemum lunulatum
  • Helianthemum × mansanetianum
  • Helianthemum × mariano-salvatoris
  • Helianthemum marifolium
  • Helianthemum maritimum
  • Helianthemum marminorense
  • Helianthemum marmoreum
  • Helianthemum mathezii
  • Helianthemum × monspessulanum
  • Helianthemum × montis-bovis
  • Helianthemum morisianum
  • Helianthemum motae
  • Helianthemum × moyense
  • Helianthemum × murbeckii
  • Helianthemum neopiliferum
  • Helianthemum nummularium - common rockrose
  • Helianthemum obtusifolium
  • Helianthemum oelandicum - alpine rockrose, hoary rockrose
  • *Helianthemum oelandicum subsp. alpestre
  • *Helianthemum oelandicum subsp. italicum
  • *Helianthemum oelandicum subsp. oelandicum
  • *Helianthemum oelandicum subsp. orientale
  • *Helianthemum oelandicum subsp. rupifragum
  • Helianthemum oelandicum
  • Helianthemum ordosicum
  • Helianthemum origanifolium
  • Helianthemum pannosum
  • Helianthemum papillare
  • Helianthemum patens
  • Helianthemum pergamaceum
  • Helianthemum × petrerense
  • Helianthemum polyanthum
  • Helianthemum polygonoides
  • Helianthemum pomeridianum
  • Helianthemum × protodianicum
  • Helianthemum × pseudodianicum
  • Helianthemum pugae
  • Helianthemum raskebdanae
  • Helianthemum × rigualii
  • Helianthemum rossmaessleri
  • Helianthemum rotundifolium
  • Helianthemum ruficomum
  • Helianthemum salicifolium
  • Helianthemum sancti-antoni
  • Helianthemum sanguineum
  • Helianthemum sauvagei
  • Helianthemum schweinfurthii
  • Helianthemum scopulicola
  • Helianthemum sicanorum
  • Helianthemum sinuspersicum
  • Helianthemum somalense
  • Helianthemum songaricum
  • Helianthemum speciosum
  • Helianthemum squamatum
  • Helianthemum stipulatum
  • Helianthemum strickeri
  • Helianthemum × subhispidulum
  • Helianthemum × subviscosum
  • Helianthemum × sulphureum
  • Helianthemum supramontanum
  • Helianthemum syriacum
  • Helianthemum syrticum
  • Helianthemum teneriffae
  • Helianthemum tholiforme
  • Helianthemum thymiphyllum
  • Helianthemum × triregnorum
  • Helianthemum ventosum
  • Helianthemum vesicarium
  • Helianthemum violaceum
  • Helianthemum virgatum
  • Helianthemum viscarium
  • Helianthemum viscidulum
  • Helianthemum × xixonense
  • ''Helianthemum zheguliense''