Elder (Sambucus nigra)

Elder (Sambucus nigra) is a shrub or small tree up to 10 m tall that readily colonises open spaces and prefers base-rich soils rich in nitrogen and phosphorus. It is often associated with rabbit warrens and eutrophic soils (i.e. soils overly rich in nutrients) and is pollution resistant. It is also mildly salt tolerant and so can grow on the banks of tidal rivers, in coastal locations and near salt-marshes (as in the example pictured above). It occurs in graveyards, on rubbish-tips and on chalky soils. The roots sometimes have mycorrhizas associated with them, but not always.

The bark of Elder is brownish-grey, smooth when young with prominent lenticels, deeply fissured and corky when old. The lenticels are of Esau's 'type 2': consisting of a loosely structured mass of suberised cells with a compact layer of suberised cells laid down at the end of the season.

The root and heartwood are said to be as hard as ebony, but young branches are hollow and filled with very light pith. Heartwood is formed by 6 to 10 years of age. The wood is diffuse-porous, as the early vessels are only slightly larger than the later vessels (though rings are visible) and contains many living fibers and small diameter vessels (about 20 to 60 micrometers in diameter). Root wood has larger diameter vessels (averaging about 85 micrometers). The Elder is characteristically a rather crooked tree with multiple stems. Young Elder trees have numerous branches coming from the base (induced by cold) many of which branch again. By about 20 to 30 years of age this basal branching stops and a single trunk becomes dominant. Elders are fast growing but short-lived. They typically live for about 25 years, but one specimen was recorded as 44 years of age. Flowering usually begins by the age of 3 or 4 years.

The leaves have stomata only on the lower leaf surface (and occasionally a few on the adaxial surface of the petiole). The leaf epidermis bears scattered unicellular hairs and adaxially the epidermis is polygonal, abaxially sinuous. (Some studies suggest that the pattern of leaf epidermis in plants in general may be partly determined by mechanical forces acting on the developing leaf). Sun leaves have a higher stomatal density than shade leaves.

The leaves of elder produce cyanogenic glycosides (sambunigrin, zierin and holocalin) and when the leaves are damaged enzymes release cyanide from these glycosides as toxic hydrogen cyanide gas. This is clearly an anti-herbivory defense mechanism. Nevertheless, deer will graze elder, but rabbits generally find it unpalatable.The bark also contains toxins, including lectins and ribosome-inactivating proteins (RIPs) which if ingested can inhibit protein synthesis in cells. Indeed, the type 2 RIPs account for about 80% of bark protein. These type 2 RIPs consist of a lectin component (B chain) that binds the surface of target cells and the A chain (a type I RIP) that enters the cytoplasm of the target cells and inhibits protein synthesis killing the cell.

Individual Elder leaves have been known to live for 196 days. They emerge in late winter / early spring (February / March in the British Isles). The leaves are compound and pinnate with 2 to 3 pairs of rounded/oval leaflets which sometimes have deeply toothed margins.

The flowers emerge in late spring, around May or June in the British Isles, in dense flat-topped clusters. The fruits form around July and ripen by early September. The flowers have no nectaries; instead there are stalk-like extrafloral nectaries (up to 10 mm long) on the nodes of the stem between the leaf bases and bases of leaflets near to the inflorescences (flowering shoots). The flowers are pentamerous (with 5 parts in each whorl) and actinomorphic. The flowers are visited by various beetles, flies and honeybees.

The berries are generally considered edible. Ripe cooked elderberries are quite edible. Raw berries are said to be able to cause nausea, vomiting and diarrhea (though personally I have never had ill effects from eating a handful of them) and the unripe berries are poisonous. This toxicity is due to low concentrations of a RIP which is denatured by boiling. Elderflower juice makes excellent white wine whilst elderberry juice makes an excellent red wine (both surpassing the grape in my own humble opinion). Several different varieties also exist.

The yield of fruit depends on the availability of nitrogen and light. The berries are eaten by birds. With the fruit pulp intact, germination rates are quite low but this increases greatly when the fruit pulp is removed or when the seed is regurgitated or defecated by birds. Germination is of the epigeal type (meaning the cotyledons emerge above ground) and the seedling bears two cotyledons (embryonic leaves). It is estimated that a mature elder can produce over 100 000 fruit in a season.

Shoot cuttings / broken shoots will readily root.

Elders support a variety of epiphytes. Seen below is the lichen Xanthoria parietina, usually yellow or greenish in color, in shade it may adopt the grey color of the fungus host. The Jew's Ear or Jelly Ear fungus (Auricularia auricula-judae) - named after Judas from biblical story, and its ear-lobe like shape and flexible structure, rather than out of racist intent - prefers Elder, growing on dead wood and older trees.

Elder bark holds an unusually high amount of moisture which may account for its distinctive and extensive epiphyte flora, including lichens and mosses.

Sambucus is now generally classified in the family Adoxaceae (Moscatel family) along with Adoxa and Viburnum.

Elderberry extract (sold as 'Sambucol') appears to have significant antiviral effects, particularly against influenza when taken orally in modest dose. At least one meta-analysis reports significant benefit (a large effect size) against upper respiratory tract viral infections. This should be investigated further by future research, including isolation of base compounds for further drug development.

The inflorescence is a flat-topped corymb with 5 primary rays.

Elder Ecology

 

References

Atkinson, M.D. and Atkinson, E. 2002. Biological flora of the British isles: Sambucus nigra L. Journal of Ecology 90: 895–923.

Esau, K. 1976. Anatomy of seed plants, 2nd ed. Wiley (Pub.).

Porter, R.S. and Bode, R.F. 2017. A Review of the Antiviral Properties of Black Elder (Sambucus nigra L.) Products. Phytother. Res. DOI: 10.1002/ptr.5782.

Article published: 12 April 2020

Article updated: 11 Jan 2021