This site and its content are under development.

Viburnum opulus L., Guelder-rose

Account Summary

Native, frequent to locally common. Circumpolar temperate.

1881; Stewart, S.A.; Callow (or Carrick) Hill.

March to January.

Growth form and preferred habitats

Viburnum opulus is a large, broad, fairly dense deciduous shrub with numerous, erect, much branched stems up to 4 m tall. It frequently produces adventitious roots and new vertical shoots on branches close to the ground, ie they look like suckers, but are formed somewhat differently. Nevertheless, these shoots do enable the bushes to spread vegetatively and form thickets. Branches are rather short, twigs pale greyish-brown to reddish-brown, somewhat angular, faintly wrinkled, glabrous. Young shoots are pale green, often tinted brownish-purple (Sell & Murrell 2006). Guelder-rose is easily known in winter by its oppositely set, greenish-yellow buds on longitudinally ridged twigs with a very small terminal bud, smaller than the side buds (Edlin 1964).

Leaf-break occurs in April in Britain and the leaves are opposite, ovate, and divided into three to five large lobes with their margins irregularly and shallowly toothed. The leaves are similar in shape to those of Sycamore (Acer pseudoplatanus) and other Maples (Acer spp.), but the leaves of V. opulus have only three main veins at their base. The petiole is short, 1-2(-3) cm long and shallowly grooved on the upper side. Stipules pale green, parallel-sided but acute-tipped, fused with the petiole and diverging from it 1-3(-5) mm above the leaf base.

There are also glands (extra-floral nectaries) at the base of each leaf-blade. These are variable both in size (0.5-1.0 mm) and number, on some leaves up to five pairs and/or extending onto the edge of the leaf blade (lamina). Often nectaries in a 'pair' are somewhat offset along the petiole (Kollmann & Grubb 2002). In autumn, the leaves turn a beautiful flaming red before they fall (Lang 1987).

Guelder-rose is a characteristic deciduous shrub of old hedgerows, scrub and broad-leaved woods, preferring moist clay soils. It is also found in wet woods and fen carr around lakeshores and on stream-sides in lowland areas; for this reason, the alternative English common names 'Water Elder' and 'Swamp Elber' are more appropriate than 'Guelder-rose', which really refers to the famous totally sterile horticultural cultivar. V. opulus is widespread throughout most of B & I, particularly on calcareous to neutral soils. It tends to avoid light and chalk soils. Horticultural cultivars, of which there are about a dozen, are frequently planted in gardens and parks and, undoubtedly, in many cases 'wild plants' have originated from cultivated forms that have been bird-sown beyond the garden wall (Lang 1987). The established strategy of the species is categorised as SC meaning it is a Stress-tolerant Competitor (Grime et al. 1988, 2007).

Flowering reproduction

The flowering period is from late-May to mid-July and inflorescences are terminal, flat-topped clusters of flowers borne on glabrous or shortly glandular stalks, 1-4 cm long, above the highest pair of leaves. The inflorescence is a flat, umbel-like, erect, compound cyme, 5-10 cm across, composed of two types of flower of unequal size. The outer ring of flowers in each inflorescence are irregular, enlarged, 15-20 mm in diameter, composed of five sepals and five creamy-white petals. However, these outer flowers are entirely sterile, lacking both stamens and pistils. The purpose of the outer flowers is to advertise and attract insect visitors to the very much smaller, 6 mm diameter, inconspicuous, inner, green or yellowish-whitish, fertile flowers, each of which has five stamens and an inferior pistil, is slightly fragrant, and produces a scarce supply of nectar at the surface of the carpels to reward visiting insects (Edlin 1964; Lang 1987). Other authors are less complimentary about the flower scent, describing it as having an unpleasant and rather sickly smell (Kollmann & Grubb 2002). On the other hand, Grigson (1955, 1987) waxes decidedly poetic regarding the flower scent, "Along wet ditches, the flowers toss and sparkle in May wind. Get them close and they smell like crisply fried, well-peppered trout, if you can imagine that trouty peppery smell with a touch of sweetness.".

Hoverflies, solitary bees and beetles are the principal pollinators, leading to outbreeding, while selfing, although feasible, appears to be rare (Kollmann & Grubb 2002). In a Canadian study, where V. opulus is an introduced species, 49 species of insects visited the flowers, although plant bugs moved infrequently between plants and therefore did not cross-pollinate many individuals. Solitary bees appeared to be the most effective pollinators there (Krannitz & Maun 1991).

The fruit of V. opulus is a scarlet, globular fleshy drupe, each one containing a single flattened pyrene (ie a seed contained within a hard, stony fruit layer). It is carried in a broad, flat-topped corymb of 20 to 30 fruits, the individual drupes (often referred to, inaccurately, as 'berries') on very short pedicels, 1-2 mm long, and the whole cluster drooping when they slowly ripen from September onwards (Lang 1987). The drupes reflect autumn sunlight from both their smooth outer skin and their inner translucent flesh (Edlin 1964).

Seed dispersal and seedling recruitment

The edible fleshy fruit of V. opulus redden in September and look ripe from October onwards, but they remain firmly attached to their stalks and are unpluckable by birds until the end of November. In December, they become easy to pluck and are taken by birds from then onwards. Guelder-rose is thus a very distinctly winter fruit, taken by birds in the coldest months of the year, between December and February. In England, Song Thrushes are easily the most frequently attracted bird species, followed by Blackbirds and Mistle Thrushes, although these two are much less significant seed dispersers (Snow & Snow 1988). There is evidence from both England and the continent that suggests many bird species are discouraged from taking the fruit by its sour flavour (see Toxicity section below), putting it low down on the pecking priority of most. In a C European study, much of the fruit on bushes in parks and gardens was not eaten. Rather, it slowly shrivelled and fell to the ground where the seed was eaten by mice (Zedler 1954). Fruit on bushes in open country field hedges had much better chance of being taken by birds, including Song Thrushes and flocks of Fieldfares (Snow & Snow 1988).

Bullfinches are very significant Guelder-rose seed predators, the number of records of their depredations in Snow & Snow's study (57) is almost half of the total feeding records of all six seed dispersers species combined (118). Since Bullfinches often remain on a bush for a long time and destroy many more fruits than a disperser takes in one visit, their impact is greater than the actual number of recorded visits suggests. Some of the monitored bushes had the greater part of their fruit crop attacked by the Bullfinches, which leave fragments of fruit skin attached to the stalks as evidence of their negative activity (Snow & Snow 1988).

The number of drupes per inflorescence in fruit (ie the infructescence) is approximately 10-25 on well-lit shoots and, exceptionally, the number might reach around 75 under ideal growing and fruiting conditions (Kollmann & Grubb 2002). In experimental studies of recruitment from seed involving comparison of 18 woody species introduced into continuous scrub, V. opulus seedlings performed poorly (0.5 per m2), and ranked low in comparison with V. lantana (Wayfaring-tree) and the other species involved (Kollmann & Grubb 2002).

In common with most fleshy-fruited shrubs, there is no persistent dormant soil seed bank in either V. opulus or V. lantana, germination taking place in the first spring after fruiting with few additional seedlings appearing in the second spring. Most seedlings of V. opulus in the experimental scrub study appeared in the month of April (Kollmann & Grubb 2002).

Variation

The Royal Horticultural Society Index of garden plants lists twelve cultivars of various leaf colours and shapes, together with double and yellow-fruited forms ('Flavum'), and the famous sterile 'Roseum' or 'Snowball' form (Griffiths 1994). Sell & Murrell (2006) recognise three 'forma', forma opulus of the hedgerow, forma roseum (L.) Hegi, the 'Snowball Tree' or true 'Guelder-rose', and forma flavum (Horwood) P.D. Sell, with yellow fruits.

Fermanagh occurrence

There are Fermanagh records from 285 tetrads, 54% of the squares in the VC. Guelder-rose is a characteristic shrub of the Upper Lough Erne basin and it is very frequent everywhere in Fermanagh, except the more upland areas. While it is almost always found in damp or fairly wet ground, occasionally V. opulus grows in much drier sites. Locally these drier sites include old quarries (eg at Blaney, Goladoo and the quarry near Keenaghan Lough), on limestone screes (eg at Doagh) and on limestone cliffs (eg N of Poulnamadda in the Knockmore area).

Fossil record

Fossil seed of V. opulus have been recovered from the Cromer Forest Bed series and from both the Hoxnian and Ipswichian interglacials. There are two Irish records from the current interglacial (the Flandrian in Britain, or Littletonian in Ireland), zones VI and VIIa, the later of which is a Mesolithic site at Lake Derravaragh. All subsequent macrofossil records listed by Godwin (1975) are from archaeological sites that stretch from the Neolithic to Roman times.

The pollen record substantiates the Hoxnian seed records, and there are records from Galloway through the Flandrian from zone III onwards. Thus, the fossil record suggests long persistence of V. opulus especially in Scotland, where the species is at present somewhat more infrequent than elsewhere in B & I (Godwin 1975).

Toxicity

Although the translucent bright red fruits are eaten by birds and this enables efficient seed dispersal, they contain bitter substances such as tannin, resins, valerianic acid and a glycoside called viburnine. Rather surprisingly, despite all these sour-tasting compounds, the berries are only slightly toxic to humans (Lang 1987). Eating them usually produces no symptoms, but occasional poisoning occurs with vomiting and diarrhoea, as was reported for a two-year-old child who ate an unknown number of berries (Cooper & Johnson 1998).

British and Irish occurrence

V. opulus is common and widespread throughout lowland B & I in hedgerows and in damp scrub and woods including fen carr and Alnus (Alder) and Salix (Willow) thickets on neutral or calcareous soils. In Scotland, although it occurs to the north of Inverness in Sutherland and Caithness (VCs 107-109), it is nowhere common, and it is absent from the Outer Hebrides, Orkney and Shetland (VCs 110-112) (G.T.D. Wilmore, in: Preston et al. 2002). In Ireland, it is common and well scattered, especially in the N and C Midlands, but it becomes less frequent in the far west. It is also absent from the Channel Isles (New Atlas).

European and world occurrence

V. opulus is widespread across temperate Europe and W & C Asia, although while reaching 63oN in Scandinavia and sparsely as far as the Arctic Circle, it is absent from the very far north (Godwin 1975). Towards the south, around the N shore of the Mediterranean, it becomes scarce and it is absent from all of the islands, and from N Africa. However, it does penetrate well down into S Italy and is present in parts of Turkey and the Caucasus region.

There is a counterpart in E Asia referred to as var. calvescens (Rehd.) Hara. In N America, another counterpart is subsp. trilobum (Marsh.) Hult. When these two additional taxa are included, V. opulus becomes Circumpolar temperate (Hultén & Fries 1986, Map 1734).

Uses

While the fruit is edible, it does contain toxins that are decidedly bitter in taste, so it cannot be eaten fresh off the bush, despite what some early writers including Chaucer have said recommending them (Grieve 1931). In Siberia, the 'berries' were fermented with flour and a spirit distilled from them. They have also been used to flavour a paste of flour and honey in Norway and Sweden. In Canada, they were used as a substitute for cranberries in making a piquant jelly to eat with meat. The fruit has anti-scorbutic properties. The fruit turns black on drying and has been used to make ink. The wood, like that of Spindle (Euonymus spp.) and Dogwood (Cornus spp.), has been used to make skewers.

The bark also contains toxins and has been used in herbal medicine in the United States of America as a nerve sedative and as an anti-spasmodic in asthma and hysteria (Grieve 1931). In Britain, it has been used to treat nervous complaints and debility with benefit to the patient, and has been successful in treating cramps and spasms of all kinds, in convulsions, fits, lock-jaw and also in palpitation, heart disease and rheumatism. One of the alternative English common names of the plant is 'Cramp Bark' for this reason (Grieve 1931).

Names

The genus name 'Viburnum' is the old Classical Latin name for 'the Wayfaring Tree' or 'Arrow Wood', V. lantana (Hyam & Pankhurst 1995). The Latin specific epithet 'opulus' is an old generic name for the Guelder-rose, although originally it probably was applied to a species of Maple, Acer, since the leaves do resemble the latter (Gilbert-Carter 1964; Gledhill 1985; Stearn 1992). Edlin (1964) says the 'opulus' of the Latin is an unidentified tree.

The name 'Guelder-rose' originated from the town of Guelders (or sometimes Gueldres (Prior 1879), or Gelders (Britten & Holland 1886), which lies on the border between Prussia and the Netherlands. It was probably first used to describe the cultivated variety or sport of V. opulus, referred to as 'The Snowball Tree', which has a round flower-head entirely composed of the characteristic large, decorative, sterile flowers tightly packed together. This cultivar can only be propagated by layering, which involves bending its branches down to touch the ground and pegging them there until they root (Anonymous 1981a). John Gerard mentioned it, and illustrated it rather well, in his Herball (1597, 1633, p. 1424), "The Rose Elder is called in Latin Sambucus Rosea and Sambucus aquatica …. In English 'Guelders Rose' and 'Rose Elder'.". However, Gerard believed it was a double-flowered form, "by art", and sterile for that reason, requiring vegetative propagation to maintain it. As Viburnum opulus var. roseum, Snowball Tree was introduced to Britain and Ireland from Holland in the 16th century, when it was first referred to as 'Guelders Rose' by Gerard. It was described as 'Geldersche roos', ie the tree with a rose-like bloom, from the Dutch province of Guelders, the modern Gelderland (Grigson 1974). It is, of course, very little like a true rose.

Grigson (1955, 1987) points out that the name 'Guelder-rose' should really properly be applied only to the sterile garden cultivar roseum, "the familiar garden bush … splendid with its snowballs of blossom in May.". Grigson (1955, 1987) lists a total of 17 alternative English common names for the hedgerow form of V. opulus, plus an additional list of 14 further names for the sterile garden form, var. roseum.

Two of the numerous names for V. opulus that appear in Gerard's Herbal (1597, 1633), "Marrish Elder" and "Water Elder" refer to the wet ground nature of typical sites and the fact that the bush flowers in the month of May, at the same time as Sambucus nigra (Elder).

Threats

None.

References

Lang, D.C. (1987); Cooper, M.R and Johnson, A.W. (1998); Gerard, J. (1597 & 1633); Kollmann, J. and Grubb, P.J. (2002); Grime et al. 1988, 2007; Grigson (1955, 1987); Grigson 1974; Britten & Holland 1886; Prior 1879; Anonymous 1981a; Gilbert-Carter 1964; Gledhill 1985; Stearn 1992; Edlin (1964); Hyam & Pankhurst 1995; Grieve 1931; Hultén & Fries 1986; Godwin 1975; Preston et al. 2002; Griffiths 1994; Sell & Murrell (2006); Snow & Snow 1988; Zedler 1954; Krannitz & Maun 1991