South Gower Cliffs - Gower - page 84

sand on low cliffs and the second, found during a National Trust survey in 1996, on limestone cliffs. This
second population may be Riddelsdell's original group. Dillwyn (1840) also reported wild asparagus 'on
the Wormshead, and several other cliffs in Gower', and there was a record for 'sands of Broughton Bay
near Whiteford Burrows' by H. J. Riddelsdell, but it no longer exists at these sites.
The absence of a number of the common species of limestone grassland is remarkable, with tor-grass
Brachypodium pinnatum ,dwarfthistle Cirsium acaule ,uprightbrome Bromopsis erecta andmeadowoat-
grass Helictotrichon pratense all absent from the peninsula. Another common species thought to be ab-
sent,dropwort Filipendula vulgaris ,hasrecentlybeendiscoveredatanisolatedlocationonOxwichPoint.
Downy oat-grass Helictotrichon pubescens is abundant, while tree-mallow Lavatera arborea grows on
the cliffs between Mewslade and Fall Bay. This is a robust biennial up to a metre in height, with purplish
flowers.
Several uncommon limestone species are relatively abundant in Gower, including hoary rock-rose,
bloody crane's-bill Geranium sanguineum and spring cinquefoil Potentilla neumanniana. A number of
species, such as basil thyme Clinopodium acinos and horseshoe vetch Hippocrepis comosa , approach the
westernlimitsoftheirrangeinthepeninsula.ThehorseshoevetchinGoweristhescarcelate-glacialrelic
diploid,foundonlyinscatteredrefugesitesinthewest(likegoldilocksasterandhoaryrock-rose),notthe
later-arriving tetraploid of English chalkland. Other rare plant species in Gower that occur at a number of
widelyseparatedsitesonthelimestonesofwesternBritainincludethesmallrestharrow,whichalsogrows
atonesiteonthePembrokeshirelimestone,inDevonontheTorbaylimestone,andintheChannelIslands
on Guernsey and Alderney. The hoary rock-rose (Fig. 43) is recorded from Gower, Pembrokeshire, North
Wales, the west of Ireland and at two localities in northern England. Many of the species of open habitats
which have distributions of this type, and which are in many cases limited to a few favourable naturally
open refuge sites on basic soil, were more widely spread in the late and early postglacial periods when
the climate was relatively warm and open base-rich habitats were common after the retreat of the glaciers
and before the spread of the forests. Progressive acidification of the soil, the spread of woodland and the
increasingly maritime climate in Britain after the formation of the English Channel have all contributed
to the reduction in the range of the species to their present refuge sites, of which the Gower cliffs are an
excellent example.