Erica cinerea – September 23rd 2024 – (Bell-heather, sometimes called Fine-leaved Heath)
Scotland is known for its heather. Indeed, next to thistle, heather is practically a national flower1. Somewhere between 20 and 30 percent of Scotland is ‘heathland’, a term describing a wide range of plant communities where the dominant life-forms are dwarf-shrubs in the Family Ericaceae. The top three ericoid species are Calluna vulgaris, Erica tetralix and Erica cinerea. We have already written about the first two (you can read about them here and here) and now we turn attention to Bell-heather Erica cinerea.
Left: Calluna vulgaris (tiny leaves, open flowers in a spike). Right: Erica cinerea (leaves in whorls of three, flowers larger and brighter, borne in bunches). Image: Chris Jeffree.
Nearly all heathlands have a combination of Heather Calluna vulgaris and Bell-heather, Erica cinerea. Many have Bilberry (Vaccinium myrtillis) as well. ‘Heathlands’ is a broad term referring to ericaceous vegetation on acidic mineral soils whereas ‘Moorlands’ are wetter, on organic soil (peat). Moorlands usually have Erica tetralix instead of E. cinerea, as it is more tolerant of flooding.
Heathlands of all kinds are described as a type of ‘semi-natural’ vegetation. They are derived from forests which were mostly cleared by fire several thousands of years ago (in the Neolithic). They are maintained by burning and grazing. From the 19th Century, the shepherds and gamekeepers would burn patches of heather every ten years or so, to encourage fresh growth and destroy tree seedlings. Some of the vital nutrients are lost in the smoke, and on steep slopes there would have been erosion of the soil.
Detail of flowers. Left: flowers of Calluna are open with distinct petals and prominent stigma and anthers; Right: urn-shaped flowers of Erica cinerea (petals fused to form the ‘bell’ protecting stigma and anthers within. Images: Chris Jeffree.
Bell-heather is an evergreen shrub, usually less than 50 cm tall. The leaves are narrow, in whorls of three, and their margins are turned down in much the same way as Erica tetralix and Calluna vulgaris. Its shoots begin to grow in the late spring and the flowers appear sooner than those of Calluna; mostly in July and August. The purple urn-shaped blooms are extremely attractive to insects, and the nectar and pollen rewards are considerable. Remarkably, it has been estimated that only four species of plant, Trifolium repens, Calluna vulgaris, Cirsium palustre and Erica cinerea together produce over 50% of all nectar in Britain (Baude et al 2016). Of course, you can buy and enjoy heather honey – it usually has a mixture of Heather, Bell-heather and other species, and an aroma which researchers tell us has more than 100 volatile compounds. The nectar is a high-octane fuel for insect flight. Access to the nectar can be a challenge as the flower’s aperture is small. Moths and bees with long tongues can reach the nectar but many insects simply cut through the side of the flower to steal nectar.
Erica cinerea in full flower. Note the margins of leaves are turned back and so the abaxial surface appears as a slit, known as the stomatal groove. Image: Chris Jeffree.
It is claimed that honey made from Erica cinerea is superior to that from Calluna vulgaris, and very good for several medical ailments. Have a look at this promotional article.
The ecology of the ericaceous species in Britain was investigated many years ago by a young student at Aberdeen University, Charles Gimingham. He was later to become the world authority on Heathlands and a Regius Professor at Aberdeen University. For his PhD project he examined the balance between Heather and Bell-heather under various grazing intensities. He found E. cinerea was dominant when there was no sheep-grazing, but under moderate grazing C. vulgaris became dominant. Under extremely high grazing, both species fared badly but C. vulgaris survived better because it adopted a bushy life-form. He supplemented his field work with laboratory experiments in which he grew seedlings and snipped them down to 1 cm using scissors to imitate the grazing action. He published a set of photographs to show how the two species responded to the treatment (Gimingham 1949). I regret I cannot reproduce them here for copyright reasons. You might be able to access his photographs here. They show how Calluna tends to form a more busy structure whereas Erica cinerea produces a small number of vertical shoots making it more vulnerable to grazing.
Heathland is usually a patchwork of age-classes produced by burning on a rotation of around ten years. This image is an example from the Pentland Hills to the south of Edinburgh. Image: John Grace.
Over several decades much progress was made towards understanding of how fire, grazing and moisture influence the development of heathlands, and this has led to firm recommendations on how to manage heathlands for commercial grouse shooting (Hobbs and Gimingham 1987, Tucker 2003); however, the emphasis has usually been on Calluna as under the current conditions it is much more abundant than E. cinerea.
British and Irish distribution of Erica cinerea. Note its absence from much of the south-east and the pale-coloured squares where it hasn’t been recorded for several years (and is presumed to be absent). Data from BSBI/Maps.
Erica cinerea can be found in several other habitats: pine forest, oakwoods, birchwoods, cliffs. Of course it is often planted in gardens, and many varieties with flower colours from white to dark purple are available.
In the BSBI Atlas 2020 it is said that Erica cinerea is declining in southern England and also more generally towards its lowland margins “through encroachment of rank grass and scrub following reduction in sheep and rabbit grazing”. Another factor which may be important for both Erica and Calluna is the deposition of nitrogen from the atmosphere. Deposition of NH3 and nitrogen oxides from farms and motor vehicles can be anything from 2 to 100 kg N per hectare per year, meaning all vegetation is currently subjected to N-fertilisation. This must surely have a negative impact on those species like Erica and Calluna that thrive in nutrient-poor environments, and a positive effect on fast-growing nitrogen-loving grasses which can be expected to take over.
Global distribution of Erica cinerea. From GBIF. It was recorded in the wild in New Zealand in 1940.
Pollen records establish this species as being ‘native’ in much of Europe (Belgium, France, Germany, Great Britain, Ireland, Italy, Netherlands, Norway, Portugal, Spain). It has been introduced to other countries (probably because the flowers make a good garden display) and now it is naturalised in Australia and New Zealand and a few locations in North America. It is considered a pest in New Zealand. We can find what the conservationists in Canterbury have to say:
“Forms a dense cover, suppressing other vegetation (including flax and snow tussock) and displacing desirable species. Profusely suckers and seeds which remain viable for at least five years. This is a very hardy plant with a wide tolerance to conditions”.
Well, I hardly recognise E. cinerea from this description as it does not form suckers. ‘Flax’ in New Zealand is Phormium tenax, a very tough plant about 2 metres tall that would surely not suffer from competition from E. cinerea. The authors go on to recommend control by
“cutting the plant close to the ground and applying metsulfuron-methyl 600g/kg (1g) + glyphosate (100ml) per litre of water or picloram gel to the fresh stump”.
The new Zealand response seems extreme, but we should bear in mind that people world-over dislike alien species, some of which can grow alarmingly well because they are far away from their natural enemies.
1.Note
For a discussion of Scotland’s national flower, see this article:
Acknowledgement
The image at the top of this page was downloaded from Wikipedia. Location is Portmahomack; Tarbat Ness, north of the lighthouse. The attribution is Ymblanter, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons.
References consulted
Bannister P (1965) Biological Flora of the British Isles. No. 100. Erica cinerea L. Journal of Ecology 53, 527–542 doi:10.2307/2257993
Baude M et al (2016) Historical nectar assessment reveals the fall and rise of floral resources in Britain. Nature 530, 85-88. doi: 10.1038/nature16532. PMID: 26842058; PMCID: PMC4756436.
Bobbink R et al. (2003) The effects of air-borne nitrogen pollutants on species diversity in natural and semi-natural European vegetation. Journal of Ecology 86, 717-738. https://doi.org/10.1046/j.1365-2745.1998.8650717.x
Gimingham C H (1949)The Effects of grazing on the balance between Erica cinerea L. and Calluna vulgaris (L.) Hull. in upland heath, and their morphological responses. Journal of Ecology 37, 100–19. https://www.jstor.org/stable/2256735
Guyot C et al (1999) Floral origin markers of heather honeys: Calluna vulgaris and Erica arborea. Food Chemistry 64, 3-11. https://doi.org/10.1016/S0308-8146(98)00122-8
Hobbs RJ (1984) Possible chemical interactions among heathland plants. Oikos. 1984 Mar 1:23-9.
Hobbs RJ and Gimingham CH (1987) Vegetation, fire and herbivore interactions in heathland. Advances in Ecological Research 16, 87-173.
Jones HE (1971) Comparative studies of plant growth and distribution in relation to waterlogging: III. The response of Erica cinerea L. to waterlogging in peat soils of differing iron content. Journal of Ecology 59, 583–591. https//doi.org/10.2307/2258333
Mallik AU and Gimingham CH (1983) Regeneration of heathland plants following burning. Vegetatio 53, 45–58. https://doi.org/10.1007/BF00039771
Marrs RH and Bannister P (1978) Response of Several Members of the Ericaceae to Soils of Contrasting pH and Base-Status.” Journal of Ecology 66, 829-340. https://doi.org/10.2307/2259298.
Rodwell JS (ed.) (1991) British Plant Communities 2. Mires and heaths. Cambridge University Press.
Thompson K and Band SR (1997) Survival of a lowland heathland seed bank after a 33-year burial. Seed Science Research 7, 409-411. doi:10.1017/S0960258500003822
