The Golden-saxifrages are saxifrages with no petals. Their flowers are tiny (a few millimetres) and are carried on very short stalks; they have four sepals which are yellowish and might easily be mistaken for petals, but they are fleshier than petals. Each flower has eight stamens and the anthers are bright yellow (you need a hand lens to see them properly, see the image). The overall ‘golden’ appearance comes from the yellowish pigmentation of the whole flower and the stamens in particular.
Chrysosplenium oppositifolium is a native plant in Britain and Europe, making its first British appearance in Gerard’s Herbal of 1597; it is a semi-aquatic perennial, producing a loose mat of creeping and rooting stems with shoots rising up to about 15 cm. It is found at sites throughout Europe except in the southern part (Spain, Italy). It has a close relative, the Alternate-leaved Golden-saxifrage which looks much like it but has leaves that are alternate on the stem rather than opposite. Sometimes they grow together, but they are distinct species with different numbers of chromosomes (2n=42, 2n =48 for opposite and alternate respectively).
Many saxifrages are rare and have acquired something of a celebrity status, partly because they mostly live in cool montane habitats and their flowers possess a delicate beauty for most folk, recalling images of summer days spent walking in the mountains. However, the Golden-saxifrages are rather common plants, and are not celebrities. Most people wouldn’t give them a second glance. Yet they clearly are of the family Saxifragaceae, having the characteristic two fused carpels. Also their leaves are quite like other saxifrages. These days however the taxonomists rely not so much on what the plants look like, but on what the DNA tells them, and how the plants cluster into ‘clades’ when their gene-similarity is revealed. I learn that the saxifrage family split up in the Oligocene about 30 million years ago, into a large clade called the Saxifragoides and another called the Huecheroides. The genus Saxifraga unsurprisingly ended up in the Saxifragoides whilst Chrysosplenium joined several genera, well known to gardeners, including Heuchera and Bergenia in the Huecheroides. If you have an appetite for cladistics you may like to read the paper by Deng et al (2015) where the phylogenetic tree shows the possible ancestry (but unfortunately the publisher is Elsevier and you will need an institutional log-in, so you may see something similar and much briefer at https://en.wikipedia.org/wiki/Saxifragaceae).
Recent taxonomic work on the Saxifragaceae has reached out further to ask about climate and habitat. The Oligocene world was warmer than today, and the Saxifragaceae probably occupied polar regions and mountain tops. The cladistic approach can be extended to attempt to derive likely climatic origins of the clades. To do this, Folk et al (2021) took 35 ‘commonly used 19 bioclimatic variables’ like temperature and precipitation and associated each with over 2000 modern members of the Saxifragaceae. Then they clustered the species based on both their current conditions and their geography, placing the result alongside the molecular phylogeny. The tribe Chrysosplenieae was classified as habitat 3, one with mesic temperature, low seasonality, high rainfall but low elevation, and these are often forest-dwelling species (Folk et al., 2021). In contrast, most Saxifrageae were classified as habitat 4, an extreme habitat classification with the coldest and driest conditions, and the highest temperature seasonality and elevation.
The reason I selected Chrysosplenium oppositifolium for Plant of the Week is that it has just started to flower. Seek, and you may find it flowering in a wet deciduous woodland, but note: it is especially vigorous in the wettest and most shaded parts of such woods, perhaps the parts that are never in sunlight and always wet. There, it presents itself as a ‘golden’ carpet. I think it is more often found in woods that are ancient. I visited one such place last week called Aldouran Glen, a mixed deciduous wood in the extreme SW of Scotland. I was delighted to find the wood several years ago as most of the old deciduous woods in this part of Scotland are gone and replaced by conifer plantations. This one has many species, including Snowdrop, Wood Anemone, Ransoms, Bluebells and others that develop rapidly in the spring, before the tree canopy has formed.
I looked up Chrysosplenium oppositifolium in Rodwell’s British Plant Communities and found it to be a characteristic plant of Alder and Ash woods. It may not be present in more acid woodland types, such as birch and certainly not in drier woodland types. However, it isn’t confined to woodlands: the BSBI describes its distribution thus:
boggy ground and seepages in woods, on streamsides, wet rocks and mountain ledges, usually in shade; also in grikes and sink-holes in limestone in the N. Pennines.
My search for the current habitat distribution continued. I was dismayed to find that the classic texts, Tansley’s The British Islands and their Vegetation and Burnett’s The Vegetation of Scotland, do not even have Chrysosplenium in their index but I was re-assured to find that the much more recent Vegetation of Britain and Ireland by Michael Proctor has several entries. He reproduces data from Keith Kirby, showing a list of those species which are found in ancient (pre-1600) woodlands. Chrysosplenium oppositifolium is in the top ten most reported species, along with Adoxa moschatellina (Moschatel), Anenome nemorosa (Wood Anenome), Lamiastrum galeobdolon (Yellow Archangel), Lathraea squamaria (Toothwort), Luzula sylvatica (Great Wood-rush) and Paris quadrifolia (Herb-Paris).
I wondered how the small flowers of Chrysosplenium oppositifolium are pollinated. I found there is a group of tiny flies (the moth-flies, family Psychodidae) also called the drain-flies because they fly around drains and sewers. They are true flies, nothing to do with moths, except they have hairy wings that give a moth-like appearance. They visit Chrysospleniums. On a Czech website (https://pladias.cz) there is much more information regarding pollination: “other Diptera (other Hymenoptera, hoverflies, butterflies, beetles, thrips”. Elsewhere I found mention of creeping visitors, namely, snails. The flowers are so open that any small creature might come for nectar and effect pollination and possibly aid seed dispersal. Probably reproduction is mostly vegetative: the stems run along the ground and sprout roots, much as water-cress does.
Some readers may want to know the etymology of the word Chrysosplenium. The Greek is chryso (Golden) and the New Latin splenium, hence “golden spleen”, referring to the flower colour and assumed medical uses.
I have read a foraging blog that says you can use the plant in salad or boiled. Having nibbled a small piece, I cannot recommend this practice. The leaves are bitter.
References
Deng J et al. (2015) Phylogeny, divergence times, and historical biogeography of the angiosperm family Saxifragaceae. Molecular Phylogenetics and Evolution 83, 86-98.
Folk RA et al. (2021) Biogeography and habitat evolution of Saxifragaceae, with a revision of generic limits and a new tribal system. Taxon 70, 263-285.
Proctor M (2013) Vegetation of Britain and Ireland. Volume 122 of the New Naturalist Series. Collins, London.
©John Grace
Botany in Scotland 
John, Thanks for your detailed write up – very interesting!
Just a note on edibility and palatability. I’ve tried the plant a few times and sometimes it is very bitter and sometimes it is actually quite nice, or at least worth putting in a salad. I think it may be to do with how hot it is, or possibly the time of year. I’d be a bit more concerned with the possibilty of picking up parasites from the damp area though, since the plant is so low growing. I know this can be a real issue with watercress.
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