Ericatetralix(cross-leaved heath) – risk assessment notes

Originates fromwestern Europe. Erica tetralix is the most northerly occurring heath occurring up as far as NW Norway (Nelson 2011, GBIF 2015).This species withstands waterlogging - very wet conditions (Underhill 1971, Nelson and Coker 1974).

Domestication/Cultivation

1.01.Species highly domesticated?

Yes

1.02.Naturalised where grown?

Yes (Nelson 2011)

1.03.Weedy races?No, none confirmed (Nelson 2011)

Climate and distribution

2.01. Suited to Australian climates? Yes, Climatch (using source location map fromNelson (2011) indicates very strong suitability to approximately 50% of Tasmania, and very strong/strong suitability to other parts of southern Australia, especially southern Western Australia, Victoria and southern New South Wales (and ACT) (see Figure 1).E. tetralix is given a score of 2 for this criterion.

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

2.03. Broad climate suitability?Yes. Source of origin is from as far north as Norway southward to France, UK, Ireland, Portugal, and Spain (Nelson 2011). It is found to an altitude of 2200 metres in the French Pyrenees (Nelson 2011). Climatch indicates high to very high suitability in several distinct climate areas (under the Koppen-Geiger system) in southern Australia – SW Western Australia, South Australia, Victoria, New South Wales and Tasmania. 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 one example of its native region (central Spain), the driest quarter of the year averages less than 50mm ofrainfall(for example in Ciudad Real and Madrid) (World Weather Online 2015, World Weather Online 2015a). Also, this species is very frost hardy with a maximum frost-resistance of about -20 degrees Celsius (Nelson 2011).

2.05. History of repeated introductions outside natural range?Yes, naturalised ineastern North America. In the USA is has been recorded naturalised in Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, North Carolina, Ohio, and West Virginia (GBIF 2015). Also naturalised/weedy in Europeand former Czechoslovakia) (Wittenberg 2005, GBIF 2015). Recently recorded as naturalised in New Zealand (Heenan et al 2008).

Weed elsewhere

3.01. Naturalised beyond native rangeYes, naturalised in eastern North America. In the USA is has been recorded naturalised in Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, North Carolina, Ohio, and West Virginia (GBIF 2015). Also naturalised/weedy in Europe (e.g. Switzerland and former Czechoslovakia) (Wittenberg 2005, GBIF 2015). Recently recorded as naturalised in New Zealand (Heenan et al 2008).

3.02. Garden/amenity/disturbance weed?Yes. Ornamental introduction to North America.

3.03. Weed of agriculture?No, no evidence of this to date.

3.04. Environmental weed?Yes, environmental weed (Randall 2001, Randall 2012). Locally established (with E. cinerea) in bog habitat (Tongariro National Park) in NZ. Eradication attempted but new seedlings regularly appear (Heenan et al 2008).

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.E. tetralix contains substances inhibitory to other plant species (Rice 1984). It was one of the species found to have 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. Although no specific information was found for this species, a ‘yes’ response to unpalatability was selected as the judgement was made that it is likely that E. tetralix shares the trait of other Erica species of being largely unpalatable.

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

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

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

4.08. Fire hazard?Yes, no 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, but unlikely. In cultivation it is considered to require full sun (GBIF 2015).

4.10. Grows in infertile soils?Yes, ‘in southern Britain, Erica tetralix is … to be found in drier heathlands on nutrient-deficient soils’ (Nelson 2011). Also grows in boggy habitats, open woodland, in acid soils, sometimes on limestone too (Nelson 2011). Capacity to grow in infertile soils is a consistent feature of other members of the genus. ‘Ericas are capable of normal nutrition in average soils, but become mycotrophic in soils unfavourable to the direct absorption of nutrients – such as on a heather moor, where the soil is wholly humus …’ (Underhill 1971).

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

4.12. Dense thickets?Yes, indications from research are as follows.‘In bogs, wet heaths and damp coniferous woodland, E. tetralix can become a dominant part of the flora’ (GBIF 2015). This dominating tendency is also indicated in Hampton (2008). In their natural situations, ‘E. ciliaris and E. tetralix heathlands are characterised by the high cover and stratification values of the shrub species. Bare ground is scarce ... (Munoz et al 2010). Related species E. lusitanica and E. arborea are recorded to form dense thickets too (Muyt 2001, Johansson et al 2009, Nelson 2011).

Plant Type

5.01. AquaticNo

5.02. GrassNo

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,discussion of reproduction by seed in Nelson (2011). Reproduction by seed is a common feature of this genus (for example, Erica lusitanica (Muyt 2001).

6.03. Hybridised naturally?Yes, hybridised with E. ciliaris to become Erica X watsonia, with E. mackayana to become Erica X stuartii, and with E. vagans to become E. X williamsii (Nelson 2011).

6.04. Self-compatible or apomicticUnknown

6.05. Specialist pollinators?No (Nelson 2011).

6.06. Reproduces by vegetative fragmentation?No, no documented evidence of this 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 no specific information was found for E. tetralix, for related species like 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 relatedE. 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, but it may be possible given the sticky hairs found on this species, and recognised capacity for these to adhere to fur (Nelson 2011).

7.06. Dispersed by other animals? Yes, very likely due to sticky hairs found on the leaves of this species. ‘it was not the individual seeds that adhered to fur but the flower heads or even whole branches’ (Nelson 2011).

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,no direct record, but very likely given 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 plantsproduce ‘many thousands of seeds… each year’ (SANBI 2010), and this level of seed production was found for E. lusitanica (DPIPWE 2015).

8.02. Persistent seed bank?Yes,E. tetralix seed in Belgium was found beneath heavily fertilised grassland reclaimed from heath 20 years previously’ (Thompson 1993, p. 235).In New Zealand ‘eradication was attempted, but new seedlings regularly appear (Heenan et al 2008). 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).

8.03. Well controlled by herbicides?Unknown, no documented evidence of this found for E. tetralix.

8.04. Benefits from mutilation/cultivation?Unknown, though is a resprouter with ‘high resrouting intensity’ (Munoz et al. 2010, p.78).

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

Figure 1. Climatch assessment for E. tetralixusing source location map from Nelson (2011). Climatch conducted by Michael Noble 22 April2015.

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.

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.

Global Biodiversity Information Facility (GBIF) (2015). Erica tetralix L.. (accessed 22 April 2015).

Hampton, M. (2008). Management of Natura 2000 habitats. 4010 Northern Atlantic wet heaths with Erica tetralix. European Commission. (accessed 22 April 2015).

Heenan, P.B., de Lange, P.J., Cameron, E.K., and Parris, B.S. (2008). Checklist of dicotyledons, gymnosperms, and pteridophytes naturalised or casual in New Zealand: additional records 2004-06. New Zealand Journal of Botany 45, pp. 257-283. (accessed 22 April 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.

Munoz, A., Alvarez, R., Pesqueria, X.M., Garcia-Duro, J., Reyes, O. and Casal, M. (2010). Burning in the management of heathlands of Erica ciliaris and Erica tetrlix: effects on structure and diversity. Nova Acta Cientifica Compostelana (Bioloxia), 19, pp. 69-81.

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.

Nelson, E.C. and Coker, P.D. (1974). Ecology and status of Erica vagans in County Fermanagh, Ireland. Botanical Journal of the Linnean Society 69, pp. 153-195.

Randall, R. (2001). Garden thugs, a national list of invasive and potentially invasive garden plants. Plant Protection Quarterly 16(4), pp. 138-171.

Randall, R.P. (2012). A global compendium of weeds (2nd Ed.). Department of Agriculture and Food, Western Australia. (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.. (accessed 10 February 2015).

South African National Biodiversity Institute (SANBI) (2008). Erica caffra L. (accessed 9 April 2015).

Thompson, K. (1993). The functional ecology of seed banks. In ‘Seeds – the ecology of regeneration in plant communities.’ Ed. M. Fenner, pp. 231-258 (CAB International, Oxon, UK).

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.

Underhill T.L. (1971). Heaths and heathers; Calluna, Daboecia and Erica. David & Charles, Newton Abbot, United Kingdom.

Wittenberg, R. (ed.) (2005). An inventory of alien species and their threat to biodiversity and economy in Switzerland. CABI Bioscience Switzerland centre report to the Swiss Agency for Environment, Forests and Landscape, Bern. URL: (accessed 22 April 2015).

World Weather Online (2015).Ciudad Real monthly climate average, Spain. URL: (accessed 22 April 2015).

World Weather Online (2015).Madrid monthly climate average, Spain. URL: (accessed 22 April 2015).