Erica erigena (Irish heath) – risk assessment notes

Originates from western Europe including Spain, Portugal, France and Ireland (Nelson 2011).

Domestication/Cultivation

1.01.  Species highly domesticated?

Yes, ‘cultivated since at least the 1830s (Nelson 2011)

1.02.  Naturalised where grown?

Yes, naturalised in England from cultivation (Randall 2012)

1.03.  Weedy races? No, no evidence of this found.

Climate and distribution

2.01. Suited to Australian climates? Yes, Climatch (using source location map from Nelson (2011) indicates strong suitability to parts of Tasmania and other parts of southern Australia, especially Western Australia, Victoria, South Australia, Australian Capital Territory and southern New South Wales (see Figure 1). E. erigena is given a score of 2 for this criterion.

2.02. Quality of climate match data? Basic (Climatch) model used (Figure 1), but source location data (Nelson 2011) is very precise. Quality good. Score of 2.

2.03. Broad climate suitability? Yes. Source of origin is western Europe (including Spain, Portugal, France and Ireland) (Nelson 2011). Climatch indicates strong suitability in several distinct climate areas (under the Koppen-Geiger system) in southern Australia – the south of Western Australia, Victoria, South Australia, Australian Capital Territory and southern New South Wales (see Figure 1). A ‘yes’ answer to this criteria requires an indication of broad climate suitability from a climate matching program or natural occurrence in 3 or more distinct climate categories.

2.04. Native/Naturalised in regions with extended dry periods? Yes, in its native region (e.g. around southern Spain), the driest quarter of the year averages less than 50mm of rainfall (World Weather Online 2016).

2.05. History of repeated introductions outside natural range? Yes, introduced to Britain (Nelson 2011). Unconfirmed theory that the species was accidentally introduced to Ireland in mediaeval times (Nelson 2011).

Weed elsewhere

3.01. Naturalised beyond native range Yes, naturalised in Britain and possibly Ireland (Nelson 2011).

3.02. Garden/amenity/disturbance weed? Yes. E. erigena is ‘an opportunist, colonising old railway embankments, cutover bogs, and even lough shores laid bare by falling water levels (Nelson 2011, p.124). ‘Man’s activities certainly assist its spread’ (Nelson 2011, p.124). Recorded for ‘cultivation escape’ (Randall 2012).

3.03. Weed of agriculture? No

3.04. Environmental weed? No, though its capacity to escape cultivation and naturalise (Nelson 2011, Randall 2012) indicate likely potential to become an environmental weed.

3.05. Congeneric weed? Yes, same genus as Spanish heath and other weedy heath species

Undesirable traits

4.01. Spines, thorns, burrs? No

4.02. Allelopathic? Yes. Erica species are recognised as having allelopathic properties that inhibit grasses and crop plants (Rice 1984).

4.03. Parasitic? No, no documented evidence of this found.

4.04. Unpalatable to grazing animals? Yes. In the context of Tasmanian grazing lands, though it may be browsed by livestock, the species would not be considered ‘palatable’. Hence, the response given above.

4.05. Toxic to animals? No, no evidence of this.

4.06. Host to pests and pathogens? No, no evidence of this found.

4.07. Toxic to humans? No, no documented evidence of this found.

4.08. Fire hazard? Yes, no direct documented evidence but ‘yes’ response based on related species E. baccans and other Erica sp. recorded to ‘increase fire risk’ and be ‘highly flammable’. (Blood 2001, Cancellieri et al 2005, Johansson et al 2009).

4.09. Shade tolerant? Unknown

4.10. Grows in infertile soils? Yes, grows in shallow gullies and on rock ledges in Spain, and within a few metres of the ocean in Ireland (Nelson 2011). ‘Lime-tolerant, even though in Ireland it is often found in the wettest, and so presumably the most acidic, parts of blanket bogs, often partly submerged in winter’ (Nelson 2011, p.125).

4.11. Climbing or smothering habit? No, no documented evidence of this found.

4.12. Dense thickets? Yes, ‘upright, bushy shrub’ (Nelson 2011, p.110), vigorous and to 3.6m tall (Knight 1995). Considered also for this response is that related species E. lusitanica and E. arborea are recorded to form dense thickets (Muyt 2001, Johansson et al 2009, Nelson 2011).

Plant Type

5.01. Aquatic No

5.02. Grass No

5.03. Nitrogen fixing woody plant? No

5.04. Geophyte? No

Reproduction

6.01. Reproductive failure in native habitat? No, no evidence found.

6.02. Viable seed? Yes, reproduction by seed is a common feature of this genus - for example, Erica lusitanica (Muyt 2001).

6.03. Hybridised naturally? No, ‘not known to have formed any natural hybrids’, but hybridises ‘readily’ with E.carnea in cultivation to form E. X darleyensis (Nelson 2011 p. 115 and 110). These two species do not hybridise in the wild as their populations do not geographically overlap (Nelson 2011).

6.04. Self-compatible or apomictic Unknown

6.05. Specialist pollinators? No, no evidence found to suggest this.

6.06. Reproduces by vegetative fragmentation? No, no evidence found.

6.07. Minimum generative time? Unknown

Dispersal

7.01. Dispersed unintentionally? Yes, as with E.scoparia, seed ‘very fine and would be easily transported by water and on roadworks equipment’ (Baker 2005).

7.02. Dispersed intentionally by people? Yes, grown as an ornamental and potentially dumped in garden waste.

7.03. Produce contaminant? No, no documented evidence of this found.

7.04. Wind dispersal? Yes, though there is no direct evidence for this species, related species are wind dispersed - like E. vagans ‘low wind dispersal’ (Canals and Sebastia 2004), and E. caffra, ‘the seeds are dispersed by the wind’ (SANBI 2008). Also, Carr et al (1992) and Blood (2001) list wind as a mechanism of dispersal for related E. baccans.

7.05. Propagules buoyant? Yes – based on other species such as E. baccans and E.arborea (Carr et al 1992). Light seed is likely to be buoyant in overland water flows.

7.06. Bird dispersed? No – no documented evidence of this found.

7.06. Dispersed by other animals? No, no evidence found to suggest this.

7.07. Propagules survive passage through gut? Unknown, no documented evidence of this found.

Persistence attributes

8.01. Prolific seed production (>2000/m sq.) Yes, prolific seed production is a common feature of Erica species. For example, the estimated 13000-20000 seeds per plant produced by E. glandulosa (Turner and Conran 2004). Also, E. baccans plants produce ‘many thousands of seeds … each year’ (SANBI 2010), and this level of seed production was found for E. lusitanica (DPIPWE 2015). ‘Ericaceous species … produce a large and permanent seed bank’ (Canals and Sebastia 2002).

8.02. Persistent seed bank? Yes, a persistent seed bank is a common feature of Ericas. For example, E. cinerea seed can survive 30-40 years in the soil (Turner and Conran 2004). E. baccans has a 1.6 year seed bank half-life (Holmes and Newton 2004). ‘Ericaceous species … produce a large and permanent seed bank’ (Canals and Sebastia 2002).

8.03. Well controlled by herbicides? Unknown.

8.04. Benefits from mutilation/cultivation? Unknown.

8.05. Natural enemies in Australia? Unknown, no documented evidence of this found.

Figure 1. Climatch assessment for E. erigena using source location map from Nelson (2011). Climatch conducted by Michael Noble 8 January 2016.

References

Baker, M. 2005. Weed alerts. Tasweeds incorporating Spotter 28, pp. 10-11.

Blood, K. (2001). Environmental weeds – a field guide for SE Australia. CH Jerram Science Publishers, Mt Waverley, Victoria.

Canals, R.M. and Sebastia M.T. (2002). Heathland dynamics in biotically disturbed areas: on the role of some features enhancing heath success. Acta Oecologica 23, pp. 303-312.

Cancellieri, D., Leoni, E. and Rossi, J.L. 2005. Kinetics of the thermal degradation of Erica arborea by DSC: Hybrid kinetic method. Thermochimica acta 438 (1), pp. 41-50.

Carr, G.W., Yugovic, J.V. and Robinson, K.E. (1992). Environmental weed invasions in Victoria – conservation and land management implications. Department of Conservation and Environment, East Melbourne, Victoria and Ecological Horticulture Pty Ltd, Clifton Hill, Victoria.

Department of Primary Industries, Parks, Water and Environment, Tasmania (DPIPWE) 2015. Spanish heath Erica lusitanica scoresheet. http://dpipwe.tas.gov.au/invasive-species/weeds/environmental-weeds/weed-risk-assessment-scoresheets-reports (accessed 6 February 2015).

Holmes, P.M. and Newton, R. J. (2004). Patterns of seed persistence in South African fynbos. Plant Ecology 172, pp. 143-158.

Johansson, M., Rooke, T., Fetene, M. and Granstrom, A. 2009. Browser selectiveity alters post-fire competition between Erica arborea and E. trimera in the sub-alpine heathlands of Ethiopia. Plant Ecology 207(1), pp. 149-160.

Muyt, A. (2001). Bush invaders of south-east Australia. R.G. and F.J. Richardson, Meredith, Victoria.

Nelson, E. C. 2011. Hardy heathers from the northern hemisphere – Calluna, Daboecia, Erica. Kew Publishing, Kew, UK.

Randall, R.P. 2012. A global compendium of weeds (2nd Ed.). Department of Agriculture and Food, Western Australia. http://www.cabi.org/cabdirect/FullTextPDF/2013/20133109119.pdf (accessed 6 February 2015).

Rice, E.L. 1984. Allelopathy (2nd Ed.). Academic Press Inc., Orlando, Florida.

South African National Biodiversity Institute (SANBI) (2010). Erica baccans L.. http://www.plantzafrica.com/plantefg/ericabaccans.htm (accessed 10 February 2015).

South African National Biodiversity Institute (SANBI) (2008). Erica caffra L. http://www.plantzafrica.com/plantefg/ericacaffra.htm (accessed 9 April 2015).

Turner, D. and Conran, J.G. (2004). The reproductive ecology of two naturalised Erica species (Ericaceae) in the Adelaide Hills: the rise and fall of two ‘would-be’ weeds? Transactions of the Royal Society of South Australia 128(1), pp. 23-31.

World Weather Online (2016). Malaga monthly climate average, Spain. URL: http://www.worldweatheronline.com/malaga-weather-averages/andalucia/es.aspx (accessed 14 January 2016).