Chrysosplenium oppositifolium L., Opposite-leaved Golden-saxifrage
Account Summary
Native, common. Sub-oceanic temperate.
1881; Stewart, S.A.; Co Fermanagh.
Throughout the year.
Growth form and preferred habitats
The prostrate stems of this low-growing, wintergreen perennial grow and spread forming adventitious roots, thus developing ± large clonal, carpet-like mats or cushions on woodland floors, or along pathsides in damp to fairly wet woods, and on the shaded, flushed and frequently waterlogged banks of ditches, streams and rivers. The species occupies a wide range of moderately fertile to nutrient- and base-poor soils, from those on limestone cliffs to base-poor mud, sand and grit, but it avoids strongly acidic or peaty soils below about pH 4.5 (Grime et al. 1988).
C. oppositifolium is able to tolerate both considerable shading by other plants and occasional temporary immersion by flood waters or a high water table and, while it occurs over a range of soil chemistry and reaction (pH 4.5-7.5), it most frequently grows on moderately acidic substrates (pH 5.5-6.0) (Grime et al. 1988).
Although it frequently occurs as a ground under-storey beneath the canopy of various herb species, Opposite-leaved Golden-saxifrage is especially common and abundant where vegetation cover is incomplete and patches of bare muddy soil occur. These sites are kept open by substrate instability, often involving occasional or periodic disturbance by cattle or other animals grazing and trampling the surface. Rainwater scouring, temporary submergence during heavy downpours and seasonal events such as sporadic winter flooding, also provide sufficient vegetation disturbance to enable colonisation by this little species. The plant is also commonly found in more fully lit, constantly damp, upland rock, cliff or wall situations, where lack of physical space, or a moderate degree of erosion, or other occasional disturbance helps keep ecological conditions suitably open for seedling colonisation and establishment.
The requirement for open ecological conditions is obvious and significant, limiting competition and potential replacement by vigorous, larger or more ecologically demanding species.
Fermanagh occurrence
This is a very common and widespread species throughout Fermanagh, recorded in 338 tetrads, 64% of those in the VC.
Flowering reproduction
In shaded, wet, boggy ground, Opposite-leaved Golden Saxifrage is the earliest species to flower each year, the blossom first appearing in March with anthesis reaching its peak in April and May. Early season flower production, together with its well-maintained wintergreen leaf area, enables the species to coexist with much taller herbs of damp or wet ground, including Epilobium hirsutum (Great Willowherb) and Valeriana officinalis (Common Valerian), both of which expand their leaf canopy considerably later in the season. The tiny, 3-4 mm, greenish, hermaphrodite, petal-less flowers have their parts in fours and are borne in a ± flat-topped, golden-yellow, leafy bract-subtended, sub-corymbose cyme. The flowers are protogynous (ie the female parts mature first), with 8-10 bright yellow anthers. Nectar is secreted from a disc round the two divergent styles, attracting small insects that act as pollinators, or else the flowers self-pollinate. Each small fruit capsule produces up to 30 very small seeds, and a large clonal patch of the plant may thus generate an enormous number of seeds.
Seed and vegetative dispersal
The ripe, dry capsule splits to release the abundant small seeds which, together with plant fragments detached by plant disturbance, are dispersed by wind (less likely within woodland), by floatation in run-off water and in mud transported on both animals and man.
Buried seed survival
The published survey of NW European soil seed banks contained just two samples of this very successful species: one reckoned the seed survival is transient (ie persisting less than one year), while the other record was indeterminate or non-committal (Thompson et al. 1997).
British and Irish occurrence
A combination of the three seed dispersal mechanisms mentioned above, obviously confers sufficient transport for this species, for it is certainly very common and widespread across most of B & I. However, perhaps on account of its somewhat restricted soil reaction requirement and necessity for open habitat growing conditions, C. oppositifolium is not omnipresent throughout B & I. The New Atlas hectad map displays a predominantly N & W distribution in Britain, while it is local or absent in parts of E England and the outer Scottish isles. In Ireland, Opposite-leaved Golden-saxifrage is widespread and common across most of the island, but patchy, local and less well represented in parts of the W & C (Preston et al. 2002).
European occurrence
C. oppositifolium is a European endemic species and biogeographically is a member of the Sub-oceanic Temperate element. Beyond B & I, it is widespread in W and parts of C Europe, extending eastwards to W Poland and C Czechoslovakia (Hultén & Fries 1986, Map 1039; Jalas et al. 1999, Map 3249; Sell & Murrell 2014).
Threats
None.