Helianthemum

''Helianthemum'' , known as rock rose, sunrose, rushrose, or frostweed,''Helianthemum''.
Integrated Taxonomic Information System (ITIS). is a genus of about 110''Helianthemum''.
Flora of China. 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-drained 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' (yellow)
*'Fire Dragon'
*'Henfield Brilliant' (scarlet)
*'Jubilee' (pale yellow)
*'Mrs C.W. Earle' (red)
*'Rhodanthe Carneum' (pink)
*'The Bride' (white)
*' Wisley Primrose' (primrose yellow)

Selected species

Species include:

*'' Helianthemum aegyptiacum''
*''Helianthemum almeriense''
*''Helianthemum apenninum'' – white rockrose
*'' Helianthemum asperum''
*'' Helianthemum canariense''
*'' Helianthemum canum'' – hoary rockrose
*'' Helianthemum caput-felis''
*'' Helianthemum cinereum''
*''Helianthemum coulteri'' see: Crocanthemum coulteri
*'' Helianthemum croceum''
*''Helianthemum guerrae''
*'' Helianthemum hirtum''
*'' Helianthemum hymettium''
*''Helianthemum jonium''
*''Helianthemum kahiricum''
*''Helianthemum lavandulifolium''
*'' Helianthemum ledifolium''
*'' Helianthemum leptophyllum''
*'' Helianthemum lipii''
*'' Helianthemum lunulatum''
*'' Helianthemum marifolium''
*'' Helianthemum morisianum''
*''Helianthemum nummularium'' – common rockrose
*''Helianthemum oelandicum'' – alpine rockrose ( syn. ''Helianthemum montanum'')
**''Helianthemum oelandicum'' subsp. ''alpestre'' (syn. ''H. alpestre'')
**''Helianthemum oelandicum'' subsp. ''italicum'' (syn. ''H. italicum'')
**''Helianthemum oelandicum'' subsp. ''oelandicum''
**''Helianthemum oelandicum'' subsp. ''orientale'' (syn. ''H. orientale'')
**''Helianthemum oelandicum'' subsp. ''rupifragum'' (syn. ''H. rupifragum'')
*'' Helianthemum origanifolium''
*'' Helianthemum pannosum''
*'' Helianthemum papillare''
*''Helianthemum piliferum''
*'' Helianthemum pilosum''
*''Helianthemum rossmaessler''
*''Helianthemum salicifolium''
*''Helianthemum sanguineum''
*''Helianthemum sessiliflorum''
*'' Helianthemum songaricum''
*'' Helianthemum squamatum''
*'' Helianthemum stipulatum''
*'' Helianthemum villosum''
*'' Helianthemum virgatum''
*'' Helianthemum viscarium''
*'' Helianthemum viscidulum''

References

External links

Flora Europaea: ''Helianthemum''eFloras search results for ''Helianthemum''

{{Taxonbar, from=Q162895

Malvales genera
Taxa named by Philip Miller