Solidago virgaurea L., Goldenrod

Account Summary

Growth form and preferred habitats

Solidago virgaurea is an erect, semi-rosette, perennial arising from a stout rootstock. It is easily recognised when in flower by its 70 cm tall spikes of golden-yellow flowerheads, each with up to twelve spreading ray florets and surrounded by narrow, papery-margined, greenish-brown involucral bracts arranged in many rows (Perring & Walters 1989). The stems of Solidago species are simple (ie unbranched) up until the inflorescence, which may or may not be branched (J. McNeill, in: Tutin et al. 1976)

Goldenrod is quite a frequent plant of dry, well drained, open, often shallow rocky soils on upland grassy heaths, screes, cliff ledges, rocky gullies, streamsides and rock outcrops including limestone pavement. The species displays a wide ecological range and, in addition to the latter list of semi-natural habitats, it can also occur in man-made, lowland equivalents, colonising habitats including rockfaces and waste in quarries, on walls, on railway cuttings, as well as undisturbed wasteground. Other more natural lowland habitats include woodland clearings and margins, hedgebanks and coastal clifftops. In all cases, colonisation is possible provided the habitats and soils involved are open, well-illuminated, infertile, nutrient poor and of low productivity (Salisbury 1942; Sinker et al. 1985; Grime et al. 1988, 2007).

S. virgaurea can tolerate a considerable range of soil reaction although it is most often associated with calcareous conditions. It may indeed be bimodal with respect to pH: on higher ground, it is centred on moderately acidic conditions, but it occurs occasionally on very acid soils in truly mountain regions, while, by contrast, in lowland situations, such as locally around Lower Lough Erne, it appears predominantly on neutral to basic, calcareous soils (Grime et al. 1988, 2007; Hill et al. 1999). Within this wide range of soil pH, S. virgaurea is undoubtedly associated with less fertile ground, the height of the plant varying between 10 and 60 cm, depending on the particular growing and flowering conditions.

The absence of Goldenrod in rank grassland, tall herb vegetation and grazed or fertile pastures, all indicates that the species is of poor competitive ability and it is confined, therefore, to infertile habitats, under which conditions it is capable of tolerating considerable levels of environmental stress. The established strategy of the species is categorised as S/CSR, meaning it is intermediate between a Stress-tolerator and a more balanced mix of all three plant strategies, Competitor, Stress-tolerator and Ruderal (Grime et al. 1988, 2007).

Variation

This is a phenotypically very variable species with respect to such features as plant height, degree of hairiness, leaf size, shape and degree of marginal serration, inflorescence branching and flowerhead size (Sell & Murrrell 2006). S. virgaurea is an out-breeding species so that variation within it is very marked in different habitats to the extent that numerous distinct ecotypes, eg, with respect to degree of shading, appear to have been formed. Some of these variants, if studied further in B & I, might deserve taxonomic recognition here as well as in Europe (J. McNeill, in: Tutin et al. 1976; Grime et al. 1988, 2007).

In the not so distant past, dwarf mountain forms of Goldenrod were considered by some to be worthy of specific rank, ie as S. cambrica Huds., or as a variety, var. cambrica (Huds.) Sm. (Raven & Walters 1956; Clapham et al. 1987), or, most recently, as a subspecies, subsp. minuta (L.) Arcangeli (Sell & Murrell 2006).

Throughout the range of the species, the form of the plant that inhabits lowland woods and heaths is generally nowadays regarded as subsp. virgaurea, while the plant of open, exposed habitats on mountains and coastal cliffs is subsp. minuta. This latter dwarf form is also widespread in the mountain ranges of N, C & E Europe, and also widespread in the Arctic (J. McNeill, in: Tutin et al. 1976; Sell & Murrell 2006).

Flowering reproduction

Goldenrod flowers from July to September, each plant forming a raceme or tight panicle of around 100 small, yellow flowerheads. Individual heads contain about twelve bright yellow florets, half of them entirely female and half bisexual. They are insect pollinated and self-incompatible (Burton 1980; Stace et al. 2015). A study by Salisbury (1942) found the number of achenes per flowerhead varied widely from 9-35 with an average of 21.4. The number of flowerheads per plant was only determined for a few specimens, but the average for this was 192 ± 60, so it was estimated that around 4,000 small, wind-dispersed seed were produced per plant (Salisbury 1942). The latter author quotes figures for the number of flowerheads from a study by Eklund (1929 – an incomplete reference provided) that found a small plant bore 47 flowerheads and a large one 419, which suggests a rather higher level of seed production than that described in Salisbury's data.

Either way, the relatively large number of seeds (or achenes, ie single-seeded fruits) suggested by the above data facilitates and enables the generally observed limited degree of dispersal of S. virgaurea into and colonisation of semi-natural and man-made, open, somewhat disturbed, well-illuminated habitats.

The soil seed bank survey of NW Europe contains nine estimates of S. virgaurea seed longevity, eight of them categorising it as transient (ie surviving less than one year), while the dissenter reckons it is short-term persistent (ie surviving more than one year but less than five) (Thompson et al. 1997).

Although the plant possesses a thick, branched rootstock, regeneration is entirely by seed as the plant demonstrates no ability to spread vegetatively but, instead, develops a confined tufted growth form (Grime et al. 1988, 2007).

Fermanagh occurrence

S. virgaurea is typically found in Fermanagh in dry to damp, well-drained, rocky, heathy grassland on upland moors and on scarp and on nearly bare rock cliff ledges, right to the summit of Cuilcagh. Less-expectedly, it grows on the rock and gravel shores of Lower Lough Erne. Goldenrod has also been found on quarry rock faces at Gortalughany and in Blaney Quarry near Carrickreagh. It has been recorded in 38 Fermanagh tetrads, 7.2% of those in the VC. As the tetrad distribution map shows, the species is located on rocky ground in the Western uplands and also around Lower Lough Erne, but is completely absent from the eastern half of the county. Seven tetrads have pre-1976 records only, which suggests a loss or disturbance of suitable habitat. This has not been investigated, but at some upland sites around Big Dog Td it could possibly be associated with ongoing afforestation operations.

British and Irish occurrence

S. virgaurea is widespread in the British Isles and occupies a wide range of habitats both lowland and upland. The 1962 BSBI Atlas hectad map indicated a definite western predominance, the species being depicted as absent in much of C & E England and lower lying parts of E Scotland. In Ireland, the species distribution in the same Atlas closely reflected the occurrence of high ground, with a near total absence in central parts of the island (Perring & Walters 1962, 1976).

The 2002 New Atlas map essentially presented a very similar B & I distribution overall, the only significant difference being a pattern of population decline in lowland areas of C & SE England, presumably due to habitat losses that began in the 1950s with the intensification of agriculture (G. Halliday, in: Preston et al. 2002). Although there are some gains in detail due to a more focused recording effort, an improvement in species occurrence represented at hectad level being especially obvious in W Ireland, the Atlas 2020 hectad map very much confirms the previously known species distribution, with the same pattern of lowland decline continuing in lowland Britain. Thus S. virgaurea has become a very localised species in areas where intensive agriculture predominates, this being particularly the case in arable regions of S & E England.

Upland populations in both B & I have certainly fared better than lowland ones over the same 70 year period, although there will certainly have been localised losses due to overgrazing by sheep and moorland heather management involving the use of fire (G. Halliday & K.J. Walker, in: Stroh et al. 2023).

European and world occurrence

In phytogeographical terms, S. virgaurea belongs to the Eurasian boreo-temperate element and, according to Hultén & Fries 1986, Map 1765), it forms a circumpolar species complex with S. dahurica Kitag. and S. multiradiata Ait.

S. virgaurea (both already mentioned subspecies) is distributed almost throughout Europe (but is absent from Iceland, the Faeroes, the Azores, Sicily and Crete). It also extends towards C Siberia where it is replaced by S. dahurica and in E Asia by S. virgaurea subsp. leiocarpa (Benth.) Hult. (Hultén & Fries 1986).

Uses and names

The generic name 'Solidago' comes from the Latin 'solidare', 'to make whole, heal or strengthen', for the plant is known in 16th and 17th century herbal lore as a vulnerary or wound-healing herb (Gerard 1633; Grieve 1931). In herbal use, it is also valued for its astringent and diuretic properties, particularly used for stones in the kidneys and bladder, and as a treatment for diphtheria (Grieve 1931). When bruised, the plant smells like Wild Carrot and contains saponins, flavonoids and phenol glycosides which modern pharmaceutical research (particularly from 1970 onwards) has shown possesses anti-inflammatory, anti-myotic and anti-rheumatic properties (https://www.biologicalmedicineinstitute.com/post/2019/02/28/solidago-virgaurea-european-goldenrod-or-woundwort, accessed 17/February/2024).

In their research on herbal medicines in use in B & I, Allen & Hatfield (2004) found that S. virgaurea was never (hardly ever? seldom?) used in Ireland as a wound herb, but rather the only uses for it were in the treatment of, "heart trouble, stomach upsets and kidney problems". Other Irish uses these authors then go on to mention include the use of the boiled leaves for treating colds and for pulmonary tuberculosis, as well as a more geographically widespread use – for treating flatulence!

The specific name 'virgaurea' is from the Latin, 'virga-aurea', meaning 'Golden twig', and thus the English common name 'Goldenrod' (according to Grigson (1974)) was translated and first appeared in print in the complete three part 1568 edition of William Turner's A New Herball. The name 'Goldenrod' refers to the plant's tall, straight stalk or spike of yellow flowers – although this name is also applied, equally validly, to Verbascum thapsus (Great Mullein) (Prior 1879; Britten & Holland 1886; Johnson & Smith 1946).

Threats

Habitat loss due to agricultural intensification and nitrogen oxide pollution from transport is ongoing and affects mainly or exclusively lowland populations, but excessive grazing of uplands and heath and moorland fires, aggravated by an increased frequency of uncontrolled hillside burns due to increased temperature associated with climatic change is also becoming a worrying threat to all mountain plants.

References

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