Erica discolor (bicoloured heath) – risk assessment notes

Originates from South Africa (Cape Province ‘on moist south-facing slopes on mountains in the Caledon and Bredasdorp Districts’ (Baker and Oliver 1967))

Domestication/Cultivation

1.01.  Species highly domesticated?

Unknown

1.02.  Naturalised where grown?

Yes

1.03.  Weedy races? No, none known

Climate and distribution

2.01. Suited to Australian climates? Yes, Climatch (using source location from Jstor Global Plants (2015) indicates very high and high suitability to southern Australia (see Figure 1). E. discolor is given a score of 2 for this criterion.

2.02. Quality of climate match data? Basic Climatch assessment undertaken. Score of 2.

2.03. Broad climate suitability? Yes, Climatch indicates high to very high suitability in several distinct climate areas (under the Koppen-Geiger system) in southern Australia – particularly SW Western Australia, South Australia, and Victoria. 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? No, in its native and naturalised regions, rainfall in the driest quarter is (just) more than 50mm as required for a ‘yes’ to this criterion.

2.05. History of repeated introductions outside natural range? Yes, naturalised in South Australia, Victoria and Tasmania (AVH 2014, ALA 2015).

Weed elsewhere

3.01. Naturalised beyond native range Yes, naturalised in South Australia and Victoria (AVH 2014, ALA 2015). There is a single 2011 Tasmanian record of the species in Snug, southern Tasmania (AVH 2014, ALA(c) 2015), but the 2014 Tasmanian Plant Census does not consider E. discolor as naturalised (de Salas and Baker 2014).

3.02. Garden/amenity/disturbance weed? Yes, evidence (ALA 2015) suggests this species has naturalised in Tasmania from horticultural pursuits.

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

3.04. Environmental weed? No, though there is not any documented evidence at this point, this species shows indications of potential as 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. Although no specific evidence has been found for this species, 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. 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. discolor 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, this criteria provided with a ‘yes’ response on the basis that 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, 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, 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

6.02. Viable seed? Yes, evidence such as naturalisation data (ALA 2015) and with other Erica species suggests this.

6.03. Hybridised naturally? No, no documented evidence of this found.

6.04. Self-compatible or apomictic Unknown, though ‘evidence from pollination studies in a number of ericaceous genera and Erica spp. in particular suggest that they are predominantly self-sterile or with limited self-compatibility (Turner and Conran 2004).

6.05. Specialist pollinators? No, no evidence of this.

6.06. Reproduces by vegetative fragmentation? Unknown

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, based on evidence of other Erica spp. such as E. cinerea (Soons and Bullock 2008) and E. baccans (Carr et al 1992).

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. Likely that as for E. scoparia , ‘the small seed does not have structures for … zoochorous dispersion’ (Bartolome et al 2005).

7.06. Dispersed by other animals? No – no documented evidence of this found. Likely that as for E. scoparia , ‘the small seed does not have structures for … zoochorous dispersion’ (Bartolome et al 2005).

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, based on evidence from other Erica spp. For example, ‘E. cinerea can produce up to a million seeds per m sq.’ (Turner and Conran 2004).

8.02. Persistent seed bank? Yes, based on evidence from other Erica spp. For example, E. cinerea ‘seeds can survive for at least 30-40 years in the soil (Turner and Conran 2004).

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

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. discolor using source location data from Jstor Global Plants (2015) and Victorian Government (n.d). Climatch conducted by Michael Noble 27 March 2015.

References

Atlas of Living Australia (ALA) (2015). Erica discolor Andrews URL: http://bie.ala.org.au/species/urn:lsid:biodiversity.org.au:apni.taxon:702485# (accessed 27 March 2015).

Australia’s Virtual Herbarium (AVH) (2014). Specimen: HO 565223 Erica discolour. URL: http://avh.ala.org.au/occurrence/0fc94d19-e4d4-45e1-a278-6c350a0b2718 (accessed 27 March 2015).

Baker, H.A. and Oliver, E.G.H. (1967). Ericas in southern Africa. Purnell & Sons, Cape Town, South Africa.

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

Bartolome, J., Lopez, Z.G., Boncano M.J. and Plaixats J. (2005). Grassland colonization by Erica scoparia (L.) in the Montseny Biosphere Reserve (Spain) after land-use changes. Agriculture, Ecosystems and Environment 111, pp. 253-260.

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.

CRC for Australian Weed Management 2007. Weed management guide; Managing weeds for biodiversity. Spanish heath (Erica lusitanica) and other Erica species.

de Salas, M.F. and Baker, M.L. (2014). A census of the vascular plants of Tasmania. Tasmanian Herbarium, Tasmanian Museum and Art Gallery, Hobart.

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.

Jstor Global Plants (2015). Erica discolor. URL: http://plants.jstor.org/compilation/Erica.discolor (accessed 27 March 2015).

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.

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

Richardson, R.J., Richardson, R.G. and Shepherd, R.C.H. 2007. Weeds of the south-east – an identification guide for Australia. R.G. and F.J. Richardson, Meredith, Victoria.

Soons, M.B. and Bullock, J.M. (2008). Non-random seed abscission, long-distance wind dispersal and plant migration rates. Journal of Ecology 96, pp. 581-590. URL: http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2745.2008.01370.x/abstract (accessed 25 March 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.

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