A perennial sub-shrub, found in open, dry rocky limestone grassland (of which it is a conspicuous component where it occurs), generally on S-facing slopes; also limestone crags and cliff edges. It is found on more skeletal soils than H. nummularium, and hybrid plants (H. x sulphureum) may be found in intermediate habitats at sites where both species occur. Lowland.
Although there has been no change in its 10-km distribution, H. apenninum is less frequent than formerly in some of its sites, mainly because of scrub colonisation following the decline of rabbits.
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Light (Ellenberg): 8
Moisture (Ellenberg): 1
Reaction (Ellenberg): 8
Nitrogen (Ellenberg): 1
Salt Tolerance (Ellenberg): 0
January Mean Temperature (Celsius): 5.3
July Mean Temperature (Celsius): 16.5
Annual Precipitation (mm): 873
Height (cm): 15
Perennation - primary
Life Form - primary
Clonality - primary
Count of 10km squares in Great Britain: 4
Count of 10km squares in Ireland: 0
Count of 10km squares in the Channel Isles: 0
Atlas Change Index: 0.12
RDB Species Accounts
Helianthemum apenninum (L.) Miller (Cistaceae)
White rock-rose, Cor-Rosyn Gwyn y Mynydd
Status in Britain: LOWER RISK - Near Threatened.
Status in Europe: Not threatened.
H. apenninum is a plant of steep rocky, but stable slopes over Carboniferous and Devonian limestones, where the southerly to westerly aspect and the good drainage of shallow rendzinas accentuate the warm and sunny character of an oceanic regional climate. The microclimate in which this plant occurs in Britain is probably the nearest approach on the British limestones to conditions characteristic of the Mediterranean region. Typically it occurs in short Festuca ovina coastal grassland that forms an open tussocky turf interspersed with patches of bare soil and rock outcrops. Lotus corniculatus, Pilosella officinarum, Sanguisorba minor and Thymus polytrichus are frequent associates, but most characteristic are annuals or pauciennials such as Blackstonia perfoliata, Carlina vulgaris, Centaurium erythraea and the Mediterranean-Atlantic mosses Scorpiurium circinatum and Tortella nitida. H. apenninum shows a markedly discontinuous distribution in Britain, a feature which it shares with a few other British rarities including Koeleria vallesiana and Trinia glauca, with which it often grows.
It is a conspicuous perennial, often growing abundantly in large masses, and flowering from April to July. Although plants flower freely and set abundant seed at all its British localities (Proctor 1956), the establishment of new individuals from seed appears to be a rare event. Seed is dispersed over very short distances, and a hot dry summer militates against the survival of seedlings. Vegetative reproduction has apparently not been observed in the field, but in cultivation cuttings root easily.
H. apenninum was first recorded in Britain in 1688 by Plukenet on "Brent Downs in Somersetshire near the Severn sea". It still grows there, at the place now known as Brean Down, at its maximum altitude in Britain of 90 metres. It occurs at four localities in the Mendip Hills, Somerset and at four near Torquay in Devon. It is abundant at both Brean Down and Berry Head, numbering many thousands, and is frequent at three of its other sites. Plants were deliberately introduced at Goblin Combe (Hope-Simpson 1987), and still survive there. The population appears to be relatively stable overall. In hot dry sites the plant does well, perhaps partly because competitors are few. In less xeric situations its survival is likely to depend on grazing keeping vigorous competitors in check. Nearly all colonies lie within protected sites, but grazing levels are not always ideal. Brean Down is grazed by both cattle and goats, but on most sites rabbits are clearly the most important or only grazers. Recreation and public pressure may become a local problem in the future, but at present appear to be at tolerable levels.
The hybrid H. x sulphureum (H. apenninum x H. nummularium) is recorded from one site in the Mendips, and was formerly known at Berry Head. However, the parents do not usually grow close together, H. nummularium generally occurring in more mesic grassland.
In continental Europe, H. apenninum is chiefly a montane species, occurring in the Mediterranean region from Morocco and the Iberian peninsula, to the southern slopes of the Alps and eastwards to Greece and Crete. It extends in scattered localities northwards to southern England where it reaches its northern limit.
Its distribution and ecology are further described by Proctor (1956; 1958).
R. D. Porley
Atlas text references
1978. Vergleichende Chorologie der zentraleuropäischen Flora. Volume 2. 2 vols.
1956. Biological Flora of the British Isles. No. 58. Helianthemum Mill. genus (pp. 675-677), Helianthemum chamaecistus Mill. (pp. 683-688), Helianthemum apenninum (L.) Mill. (pp. 688-692). Journal of Ecology. 44:675-692.
1999. British Red Data Books. 1. Vascular plants, edn 3.