Polygala myrtifolia L.

Title: Polygala myrtifolia L.

Scientific Name:

Polygala myrtifolia L.

Common Name:

cascade curse, myrtle-leaf milkwort, Bellarine pea

Source & more images (via ALA)

Habitat: The species is commonly found in coastal areas on shallow soils over calcrete or deep calcareous sands (Carter et al., 1990). It is known to establish in dune systems, coastal bluffs and also in shrublands and woodlands (Muyt, 2001). Furthermore it has been noted to establish in heathlands and heathy woodlands, mallee, lowland, grassland and grassy woodland, dry sclerophyll forests and riparian vegetation (Carr et al., 1992).

Distribution:

Original source via GBIF

Invasiveness Assessment

ESTABLISHMENT

1. Germination requirements? Seeds germinate in the open or under dense vegetation generally in May to June (Carter et al., 1990) but at any time of the year if sufficient moisture (Blood, 2001). However Arnold (1981) states that the seeds appear to be capable of germinating any time of the year. Seedlings that germinate in autumn tend to have a better survival rate. Germinates prolifically after disturbance such as fire (ESC, 2002) and following soil or canopy disturbance (Muyt, 2001). Seeds are able to germinate throughout the year, whilst there is a seasonal component to survival, this question only deals with germination requirements.

2. Establishment requirements? Occurs in diverse vegetation types and on may different soils (Meerow and Ayala-Silva, 2005). Most growth occurs over the cooler, moist winter period (Muyt, 2001). In South Australia all infestations are coastal, on shallow soils over calcrete or deep calcareous sands (Carter et al., 1990). All sites receive 500-700 mm annual rainfall, predominately in winter (Carter et al., 1990). Establishes in dune systems, coastal bluffs, shrublands and woodlands (Muyt, 2001). It prefers light, sandy, well-drained soils (DPI, 2007). Germinates readily in both full shade and full sun (Muyt, 2001, Carter et al., 1990). The plant is able to establish in a range of conditions but is dependent on moist periods over winter for growth.

3. How much disturbance is required? The plant establishes well in disturbed sites (Weber, 2003). Grows in both shade and full sun (Muyt, 2001). Mass germination can occur following soil or canopy disturbance (Muyt, 2001) and fire (ESC, 2002). It is unclear whether this species invades native vegetation or requires disturbed sites. Isolated satellite infestations occur in disturbed areas, extending into relatively undisturbed vegetation as a front (Carter et al., 1990). Can invade dry coastal vegetation, heathland and heathy woodland, mallee shrubland, lowland, grassland and grassy woodland, dry sclerophyll forests and woodland and riparian vegetation (Carr et al., 1992). The plant is able to establish in both disturbed and relatively undisturbed areas.

GROWTH / COMPETITIVE

4. Life form? This evergreen shrub reaches a height of 1.25 to 2 m, and maintains a tight, spherical canopy (Meerow and Ayala-Silva, 2005). Small, much branched hairless perennial (Roy et al, 1998). Belongs to the polygalaceae family (Harden, 1993).

5. Allelopathic properties?No information found.

6. Tolerates herb pressure? It does not tolerate grazing and can only establish in areas where livestock have been excluded (Carter et al 1990).

7. Normal growth rate? It grows rapidly and flowers when still young (ESC, 2002). It’s competing with coastal wattle Acacia longifolia var. sophorae (Carter et al., 1990). It is able to compete with a similar life form suggesting that its growth rate is fairly rapid.

8. Stress tolerance to frost, drought, w/logg, sal. etc? Plants tolerate salt-laden winds, exposed positions and seasonally hot, dry spells (Muyt, 2001). Hot fires kill mature plants, but seedling regeneration is rapid (Carter et al, 1990). It is tolerant of poor soils, dry conditions and exposure to salt (ESC, 2002). It prefers light, sandy, well-drained soils (DPI, 2007). Plant is tolerant to salt, drought and poor soils but is susceptible to fire and possibly waterlogging.

REPRODUCTION

9. Reproductive system? The peak flowering period is from spring to summer (Sept to Oct) in most areas where it is grown, (Meerow and Ayala-Silva, 2005; Carter et al, 1990, Muyt 2001) plant produces an abundance of 2 to 3 cm long purple flowers. However plant can flower all year round (Roy et al., 1998). Seeds germinate in May to June (Carter et al, 1990). The plant reproduces only by seed (Muyt, 2001).

10. Number of propagules produced? Two seeded capsules about 10 mm long (Roy et al., 1998). Seedling density may exceed 2,000 m2 (Weber, 2003).

11. Propagule longevity? Seeds can remain viable in the soil for two to three years (Weber, 2003, Muyt, 2001).

12. Reproductive period? Can flower and seed when less than 50 cm high (2 years old) (Muyt, 2001; Carter et al., 1990). Older plants are around 15 years old and are still in good condition at this age (van der Walt, 2003). Plant is capable of flowering for more than 10 years.

13. Time to reproductive maturity? Plants are able to set seed at the age of 2 (Muyt, 2001; Carter et al., 1990).

DISPERSAL

14. Number of mechanisms? Seed is dispersed by birds, ants, water, in soil and garden refuse (Muyt, 2001).

15. How far do they disperse? Due to bird dispersal it is very likely that at least one propagule will disperse greater than one kilometre

Impact Assessment

RECREATION

1. Restrict human access? This evergreen shrub that reaches a height of 1.25 to 2 m, and maintains a tight, spherical canopy (Meerow and Ayala-Silva, 2005). It is a highly invasive species that is able to build up large populations rapidly and can form dense mixed age thickets (Muyt, 2001). It is a robust shrub with a tight spherical structure that can be a nuisance and may impede direct human access.

2. Reduce tourism? The plant produces an abundance of 2 to 3 cm long purple flowers and can flower all year round (Roy et al., 1998) making it quite visible to visitors who conversely might perceive the plant as attractive. The dense thickets may inhibit recreational activities.

3. Injurious to people? No effect, no prickles no injuries.

4. Damage to cultural sites? The plant does not cause any structural damage however dense consistent flowering populations (Roy et al., 1998) may have a moderate visual effect

ABIOTIC

5. Impact flow? Although this is a species of coastal areas it is not known to disturb water flow or water beds. Plant establishes in dune systems, coastal bluffs, shrublands and woodlands (Muyt, 2001). It prefers light, sandy, well-drained soils (DPI, 2007). The species is essentially terrestrial so it does not occur near a water body and have no effect on water flow.

6. Impact water quality? Refer to comments in above question. No measurable effect on water quality.

7. Increase soil erosion? The plant competes with native shrubs and shades out native ground flora reducing integrity of the bushland (Carter et al., 1990). The plant generally occurs in coastal areas where soil instability is common, furthermore juvenile plants readily establish and form dense carpets under parent plants (Carter et al., 1990). Therefore the plant provides a level of soil stability within the areas it colonises.

8. Reduce biomass? The plant occupies vacant areas in the mid canopy. However being a displacing species direct replacement would be expected

9. Change fire regime? The plant is fire sensitive and killed by fire (Blood, 2001) however it germinates prolifically after disturbance such as fire (ESC, 2002) but not reliant on fire (Blood, 2001). On the basis that the biomass of a community remains stable where this plant establishes, indicates that either frequency or intensity of fire risk will remain the same. No information on plants flammability characteristics. Unlikely that the plant will increase fire risk.

COMMUNITY HABITAT

10(a) Impact on composition of high value EVC? EVC= Coastal tussock grassland (V); CMA= Corangamite; Bioregion= Otway Ranges; VH CLIMATE potential. This species has been found to establish and successfully invade coastal areas including dune systems and coastal bluffs (Carter et al., 1990; Muyt, 2001). The shrub maintains a tight spherical canopy and forms dense thickets that totally dominate the shrub canopy, overtaking native plant growth and preventing any overstorey generation (Muyt, 2001). It is an aggressive, invasive and rapid growing species that dominates the understorey in dry bush and coastal woodlands (ESC, 2002) subsequently significantly altering ecosystem composition within this stratum.

10(b) Impact on medium value EVC? EVC= Coastal sand heathland (R); CMA= West Gippsland; Bioregion= Wilsons Promontory; VH CLIMATE potential. This species has been found to establish and successfully invade coastal areas including dune systems and coastal bluffs (Carter et al., 1990; Muyt, 2001). The shrub maintains a tight spherical canopy and forms dense thickets that totally dominate the shrub canopy, overtaking native plant growth and preventing any overstorey generation (Muyt, 2001). It is an aggressive, invasive and rapid growing species that dominates the understorey in dry bush and coastal woodlands (ESC, 2002) subsequently significantly altering ecosystem composition within this stratum.

10(c) Impact on low value EVC? EVC= Heathy Woodland (LC); CMA= Wimmera; Bioregion= Lowan Mallee; VH CLIMATE potential. Isolated satellite infestations occur in disturbed areas, extending into relatively undisturbed vegetation as a front (Carter et al., 1990).Can invade dry coastal vegetation, heathland and heathy woodland, mallee shrubland, lowland, grassland and grassy woodland, dry sclerophyll forests and woodland and riparian vegetation (Carr et al., 1992). The DPI (2007) describes heathy woodland EVC within the Wimmera CMA as comprising of soils that are Quaternary sand sheets and low dunes of aeolian origin. The soils in the area are predominately deeply leached infertile sands. The species is known to do well in shallow soils over calcrete or deep calcareous sands (Carter et al., 1990) indicating that conditions within this EVC are conducive for good growth. The aggressive and invasive nature of the plant will smoother and displace native vegetation within the lower and potentially even the mid stratum.

11. Impact on structure? The species grows to heights of 2 m and occupies gaps in the shrub stratum, therefore only affecting species in the mid and understorey. Literature suggests that the species forms dense mixed aged thickets over other native species in the lower stratum (Muyt, 2001) subsequently displacing and transforming the species community in both the mid and lower strata.

12. Effect on threatened flora? The impact on threatened flora is indeterminable.

FAUNA

13. Effect on threatened fauna? The impact on threatened fauna is indeterminable.

14. Effect on non-threatened fauna? It does not tolerate grazing and can only establish in areas where livestock have been excluded (Carter et al., 1990). May provide an available food source for both livestock and native animals but its susceptibility to grazing might mean that it is not a reliable food source for livestock.

15. Benefits fauna? In some areas the plant can flower all year round, therefore can provide a year long food resource for birds (Muyt, 2001) and insects especially in times of food scarcity.

16. Injurious to fauna? The information studied suggests that the plant does not contain spines or burrs and is not toxic.

PEST ANIMAL

17. Food source to pests? There is no evidence in the literature that suggests that the plant is a food source to pests. However its year long flowering regime may be an attractive food source for pest birds. Muyt (2001) notes that the seed is dispersed by birds but does not mention what species.

18. Provides harbor? The plant can invade to form dense thick patches however not continuous. Its tight structure may have the capacity to harbour terrestrial pests such as foxes and rabbits.

AGRICULTURE

19. Impact yield? No evidence in the literature suggests that this plant invades agricultural landscapes.

20. Impact quality? No evidence in the literature suggests that it is a weed of agriculture.

21. Affect land values? Affect to land value would be minimal because no evidence suggests that it is a weed of agriculture and it does not tolerate grazing.

22. Change land use? The plant is not considered a serious weed of agriculture, therefore it would not cause serious alteration of land use.

23. Increase harvest costs? The plant is not a weed of agriculture. It is not likely to increase agricultural costs by increasing harvesting time or is not a potential contaminant in agricultural produce.

24. Disease host/vector? No information suggests that this plant is a disease vector or host.

Feedback

Do you have additional information about this plant that will improve the quality of the assessment? If so, we would value your contribution.

Assessment ratings originally made by the Victorian Department of Primary Industries.

The entry of this assessment was made possible through the generous support of Dr Robin Adair, Research Leader, Weed Sciences, Victorian Department of Primary Industries.

Attachments:

polygala via ala.JPG
Capture.JPG

referenced by (3)

wra1009: Common Name - M (via myrtle-leaf milkwort)wra997: Common Name - C (via cascade curse)wra825: Common Name - B (via Bellarine pea)

Article: wra6630 (permalink)
Categories: :wra:p, :wra:invmh, :wra:inv1, :wra:inv2, :wra:inv3, :wra:inv4, :wra:invl, :wra:inv5, :wra:invm, :wra:inv6, :wra:inv7, :wra:inv8, :wra:invml, :wra:inv9, :wra:inv10, :wra:inv11, :wra:inv12, :wra:invh, :wra:inv13, :wra:inv14, :wra:inv15, :wra:imp1, :wra:impml, :wra:imp2, :wra:imp3, :wra:impl, :wra:imp4, :wra:imp5, :wra:imp6, :wra:imp7, :wra:imp8, :wra:imp9, :wra:imp10a, :wra:impmh, :wra:imp10b, :wra:imp10c, :wra:imp11, :wra:imp12, :wra:imp13, :wra:imp14, :wra:imp15, :wra:imp16, :wra:imp17, :wra:imp18, :wra:imp19, :wra:imp20, :wra:imp21, :wra:imp22, :wra:imp23, :wra:imp24
Date: 2 December 2011; 11:06:41 AM AEDT

Author Name: David Low
Author ID: adminDavid