Angled heath (Erica quadrangularis) – risk assessment notes

Originates from South Africa (CRC for Australian Weed Management 2007)

Domestication/Cultivation

1.01.  Species highly domesticated?

Yes

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 outlined in Baker and Oliver (1967)) indicates moderate suitability to parts of Tasmania, and very strong suitability to other parts of southern Australia, especially Western Australia, South Australia and Victoria (see Figure 1). E. quadrangularis is given a score of 2 for this criterion.

2.02. Quality of climate match data? Yes, Tasmanian Climatch assessment undertaken. Score of 2.

2.03. Broad climate suitability? Yes. Source of origin includes Cape Peninsula across to Knysna and up to Malmesbury in South Africa (Baker and Oliver 1967). Climatch indicates moderate to 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. E. quadrangularis is prohibited from Western Australia (DAFWA 2015).

2.04. Native/Naturalised in regions with extended dry periods? Yes, in its native region, the driest quarter of the year averages less than 50mm rainfall (Wikipedia 2015).

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

Weed elsewhere

3.01. Naturalised beyond native range Yes, naturalised in Victoria and South Australia (CRC for Australian Weed Management 2007, SANBI 2013, Queensland Government 2015).

3.02. Garden/amenity/disturbance weed? Yes, ‘has escaped cultivation and naturalised’ (SANBI 2013).

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

3.04. Environmental weed? Yes, a ‘serious threat to one or more vegetation formations in Victoria’ (Carr et al 1992), ‘regarded as an environmental weed in Victoria, and as a potential environmental weed or ‘sleeper weed’ in other parts of southern Australia’ (Queensland Government 2015). Listed as a ‘perceived risk’ to the nationally threatened Kilsyth South Spider-orchid (Arachnorchis sp. aff. Venusta) (Department of the Environment 2015).

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. quadrangularis 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, no documented evidence of this found. However, another species E. arborea shows shade tolerance during stages of its life cycle (Ojeda et al 2000).

4.10. Grows in infertile soils? Yes, in its place of origin (South Africa) E.quadrangularis grows on ‘seepage areas on sandy flats, on lower mountain slopes and on moist clay banks’ (Baker and Oliver 1967, SANBI 2013). Though there was no further specific evidence found for this species, 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).

For example, E. arborea in its places of origin such as southern Spain and northern Morocco grows on infertile (acid sandy) soils (Ojeda et al 2000). Edaphic requirements are relatively broad for E. arborea (Ojeda et al 2000). [E. arborea] grows usually on acidic, silicious, soils but also on limestone in places of origin (Nelson 2011).

4.11. Climbing or smothering habit? No, no documented evidence of this found.
4.12. Dense thickets? Yes, ‘sometimes forms dense colonies’ in its place of origin (South Africa) (SANBI 2013). Also, 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 ‘propagate by seed or cuttings’ (SANBI 2013).

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

6.04. Self-compatible or apomictic Unknown

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

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 - Carr et al (1992) and Blood (2001) list wind as a mechanism of dispersal for related E. baccans.

7.05. Propagules buoyant? Yes – Carr et al (1992) lists water as a mechanism of dispersal for E. quadrangularis (though with a question mark). 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, though no specific information was found on this topic for E. quadrangularis, prolific seed production is a common feature of Ericas. For example, for E. baccans plants ‘many thousands of seeds are produced each year’ (SANBI 2010). Also, this level of seed production was found for E. lusitanica (DPIPWE 2015).

8.02. Persistent seed bank? Yes, though no specific information was found on this topic for E. quadrangularis, a persistent seed bank is a common feature of Ericas. For example, 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. quadrangularis.

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. quadrangularis using Cape Province – Malmsebury – Knysna locations as approximate source outline. Climatch conducted by Michael Noble 12 February 2015.

References

Atlas of Living Australia (ALA) (2015). Erica quadrangularis Salisb. http://bie.ala.org.au/species/urn:lsid:biodiversity.org.au:apni.taxon:498736# (accessed 12 February 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.

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.

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

Department of Agriculture and Food, Western Australia (DAFWA) (2015). Organism details – Erica quadrangularis Salisb.. https://www.agric.wa.gov.au/organisms/90837 (accessed 12 February 2015).

Department of the Environment (2015). National recovery plant for twenty-five threatened orchid taxa of Victoria, South Australia and New South Wales 2003 – 2007. http://laptop.deh.gov.au/biodiversity/threatened/publications/recovery/25-orchids/a-venusta.html (accessed 13 February 2015).

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.

Ojeda F., Arroyo J., and Maranon T. (2000). Ecological distribution of four co-occurring Mediterranean heath species. Ecography, 23, 148-159.

Queensland Government (2015). Angled heath Erica quadrangularis. http://keyserver.lucidcentral.org/weeds/data/03030800-0b07-490a-8d04-0605030c0f01/media/Html/Erica_quadrangularis.htm (accessed 12 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) (2013). Erica quadrangularis Salisb. http://www.plantzafrica.com/plantefg/ericaquadrangul.htm (accessed 12 February 2015).

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

Wikipedia (2015). Cape Town. http://en.wikipedia.org/wiki/Cape_Town (accessed 11 February 2015).