BSBI Species Accounts ArchiveRibes spicatum and Ribes rubrum
Mon, 09/06/2010 - 11:00 | 
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| Ribes spicatum Robson, Downy Currant.
Synonyms:
Warburg (1962) notes that some cultivated redcurrrants (R. rubrum) are (ancient?) hybrids with R. spicatum and might escape into the wild, but there is no evidence that this occurs. Although the two species occasionally coexist in the wild, I have examined several mixed populations without finding intermediates, perhaps because fruit-set in R. spicatum is rather unusual (below). Chromosome No.: 2n = 16 (Stace 2010). |
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| Photography: A.J. Richards |
Apparently curiously absent from south-east, south-west and much of western Scotland, where it should be looked for. In this context, its occurrence in high rainfall districts of Islay and northern Skye is difficult to explain. Although stated by Warburg (1962) to occasionally escape from cultivation, and to have been hybridised with redcurrants, there is little evidence that it has been cultivated in the UK in the modern era, or escapes (Webb 1993) - and records outside the native distribution and habitats should be reviewed critically. Typically, plants of R. rubrum and R. nigrum are found close to the nearest habitation, and as the natural riverside woodland is penetrated further R. spicatum finally appears. As clones can be very long-lived, it tends to be persistent in the absence of major habitat change, but is a poor coloniser in the absence of much regeneration from seed. A species of boreal woodlands, apparently extending eastwards to Manchuria (Warburg 1962).
R. spicatum is a much misunderstood and under-recorded species that is frequently mistaken for R. rubrum. Most accounts concentrate on rather obscure floral characters, but as flowering occurs very early, usually in mid April, and many plants fail to flower, an attempt at identification is often abandoned unnecessarily. A further confusion results from the loss of the fine pubescence from the upper surface of the leaf as the season progresses in R. spicatum; however, hairs usually persist on the leaf margin (lens needed). Any pubescence on leaves of R. rubrum is scattered and the hairs longer and coarser. Indumentum varies across the European range. R. glabellum has been used for glabrous arctic and subarctic varieties, while R. hispidulum from eastern Europe and Russia has small hairy leaves.
In fact R. spicatum and R. rubrum have a different ‘jizz’. The leaves of R. spicatum are matt and a rather dull, dark green; they are held characteristically at an approximate right-angle to the stem, and the old wood is dark; even blackish. In R. rubrum the leaves are shiny, a rather pale yellowish green, they are more floppy, and the wood is a pale orange-brown. The petiole is green in R. spicatum but orange-ish in R. rubrum. Definitively, the sinus of the leaf-base exceeds 90 degrees and may approach 180 degrees in R. spicatum, but is 90 degrees or less in in R. rubrum. With practice, bushes can be accurately identified from a distance of 10 m or more, even in mixed populations.
It is worth emphasising that several floral characteristics that appear in most floras seem not to be reliable. Warburg (1962) said that the inflorescence in R. spicatum is ‘erect to....spreading, but not pendant except in fruit’. However, the inflorescence is usually pendant from the first, and is never erect in my experience. The difference in hypanthium shape between ‘cup shaped (spicatum) and saucer-shaped (rubrum)’ (Stace 1997) sounds useable, but is far from straightforward unless you have the two types together. Although the absence of a visible connective to the anther in R. spicatum is a reliable character if a lens is used, it is extremely fiddly, and anthers are evanescent and lost very early in the season.
Leaves of Ribes spicatum (above) and R. rubrum (below).
Photography: A.J. Richards
Click on the map to view full-size on the BSBI Maps Scheme website.
In North-east England at least, Ribes spicatum has a narrow and distinctive habitat niche. It occurs mostly in upland areas, but at low altitudes (rarely above 200 m) in native woodland within 50 m of shallow, rocky rivers and streams, usually in ‘denes’ (steep declivities in sandstone country). It is usually rooted amongst water-borne boulders in areas where the water course regular changes position, either in raised islands or on steep banks, often in considerable shade, most usually from alders (Alnus glutinosa). It appears to compete poorly with comparable life-forms, and persists in a tension zone between the erosive powers of flooding, and the establishment of a dense, shrubby ground layer. It has a wide range of associates, but seedling sycamore (Acer pseudoplatanus), Geum urbanum, Chrysosplenium oppositifolium, Dryopteris dilatata, D. filix-mas, Allium ursinum, Urtica dioica and Luzula sylvatica are amongst the most typical. Most localities classify as W6 Alnus glutinosa-Urtica dioica woodlands (Rodwell 1991). It is noteworthy that this habitat bears little relationship to that cited in Warburg (1962) ‘Woods on limestone’ or that in Preston et al. (2002) ‘a shrub of limestone woods.......’, and although it does occur rarely in this habitat (including grikes in limestone woods) in Lancashire and Yorkshire, nevertheless, it nearly always occupies a streamside position, and is much more commonly met with in the sandstone denes of Northumberland and Durham
Ribes spicatum typically forms clonal individuals, varying from one to more than 100 stems. Large plants may cover 10 m or more and are considered to be of a considerable age. They are deep-rooted and capable of withstanding considerable flooding, although it seems that repeated flooding and root erosion can eventually lead to the death of large parts of the clone, and many individuals tend to be partially senescent. Many plants, especially those in deep shade, flower rarely, and fruit-set is usually very poor. Flowers are visited by bees, especially queen Bombus spp., but plants are probably self-incompatible. It is notable that fruit-set is best where several flowering individuals occur within a relatively small area (<100m). Seeds are presumably dispersed by birds, but in most populations evidence of regeneration by seed is absent.
- Origin: native. The berries are edible and so likely to have been informally cultivated through its native range, but replaced by R. rubrum and possibly hybrids in modern times, and rarely if ever seen in cultivation today, except possibly in eastern Europe (Webb 1993).
- Rarity: very local with a narrow habitat niche and absent from many apparently suitable sites, perhaps due to its poor colonisation abilities, but stable and persistent in most previously known sites after 50 years or more.
- Threat: probably low as most of the streamside woodlands in which it is found are unlikely to be deforested.
- Conservation: classed as an axiophyte, probably as a good indicator of ancient riverine woodland.
- Bolkhovskikh Z et al. 1969. Chromosome numbers of Flowering Plants. Acad. Sci. URSS.
- Simmonds NW. 1976. Evolution of Crop Plants. Longman, London. Webb DA. 1993. Flora Europaea I, ed.2. Cambridge UP.
Further studies might concentrate on the extent to which R. spicatum and R. rubrum remain distinct in the wild. If intermediates are found, are these the result of recent hybridisation, or do they reflect the complex origin of R. rubrum (Simmonds 1976)? These questions would probably be best answered using molecular markers such as those from AFLPs, but a simple examination of e.g. pollen stainability might indicate whether wild R. spicatum is introgressed by R. rubrum. It would be interesting to attempt to age large clonal individuals, but this may be very difficult as the plant may be far older than the oldest stem. Possibly woody stocks show annual growth rings?
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