European nettle tree (Celtis australis)

Present distribution

Scientific name:	Celtis australis (L.).
Common name(s):	European nettle tree

This weed is not known to be naturalised in Victoria

Habitat:

Dominate riparian vegetation (Agnote 2009). Mediterranean woodlands and shrublands, montane vegetation (FLIS 2009). No waterlogging (AANF 2009) Cannot grow in shade, well drained, light (sandy) medium (loamy) soils, tolerates nutrient poor (Wiki 2009). Mod. Salt tolerance (UNFL 2009). Drought tolerant (Wiki 2009). Frost tolerant (Blood 2001). 500mm rain (AANF 2009). Invades pine plantations (Blood 2001). Potential weed of agriculture (Agnote 2009).

Potential distribution

Potential distribution produced from CLIMATE modelling refined by applying suitable landuse and vegetation type overlays with CMA boundaries

Map Overlays Used

Land Use:
forestry; horticulture perennial

Ecological Vegetation Divisions
lowland forest; damp forest; riparian; wet forest; high altitude shrubland/woodland; granitic hillslopes; rocky outcrop shrubland; riverine woodland/forest;

Colours indicate possibility of Celtis australis infesting these areas.

In the non-coloured areas the plant is unlikely to establish as the climate, soil or landuse is not presently suitable.

Red= Very high	Orange = Medium
Yellow = High	Green = Likely

Impact

QUESTION	COMMENTS	RATING	CONFIDENCE
Social
1. Restrict human access?	Can grow 20 or 25 meters in height (Wiki 2009). Bark is thin and easily damaged from mechanical impact; droop as the tree grows, and will require pruning for vehicular or pedestrian clearance beneath the canopy (UNFL 2009). Can form dense thickets and dominate riparian vegetation (Agnote 2009). Major impediment to access waterways or machinery. Significant works required to provide reasonable access, tracks closed or impassable.	h	mh
2. Reduce tourism?	Fruits are hard and people can roll and slip on them when they drop onto sidewalks and other hard surfaces (UNFL 2009). Trunk and branches susceptible to breakage (UNFL 2009). Can form dense thickets and dominate riparian vegetation (Agnote 2009). Some recreational uses affected.	mh	mh
3. Injurious to people?	No spines, burrs, toxins (PFAF 2009; Agnote 2009). No effects. No effect, no prickles, no injuries.	l	mh
4. Damage to cultural sites?	Trees have deep spreading roots (PFAF 2009) – therefore may cause damage to some structures such as footpaths. Moderate structural effect.	mh	mh
Abiotic
5. Impact flow?	A deciduous tree (Wiki 2009). Fruit, twigs, or foliage cause significant litter (UNFL 2009). Invades riparian zones (Agnote 2009). Likely to cause litter build up in streams, especially small streams would suffer reduced flow rate in those areas. Minor impact on surface or subsurface flow either by roots or free floating aquatics.	ml	mh
6. Impact water quality?	A deciduous tree (Wiki 2009). Fruit, twigs, or foliage cause significant litter (UNFL 2009). Invades riparian zones (Agnote 2009). Moderately dense crown (Agnote 2009), therefore reduction in light reaching the surface. Noticeable but minor effects in either dissolved 0₂or light levels.	ml	mh
7. Increase soil erosion?	Can form dense thickets and dominate riparian vegetation (Agnote 2009). Moderate probability of large scale soil movement.	ml	mh
8. Reduce biomass?	Can form dense thickets (Agnote 2009). Biomass may increase.	l	mh
9. Change fire regime?	Can form dense thickets (Agnote 2009). – Not enough information.	m	l
Community Habitat
10. Impact on composition (a) high value EVC	EVC = Valley Grassy Forest (E); CMA = North East; Bioregion = Highlands Northern Fall; VH CLIMATE potential. “Invasive trees such as Celtis, are among the most damaging to the natural ecosystem, as a result of their ability to become structurally dominant.” (Agnote 2009). It out-competes and replaces native shrubs and trees (Agnote 2009). Some of the same species of birds, also feed during the same period on fruit of Camphor Laural. This may significantly enhance the dispersal of Celtis throughout the disturbed, regenerating riparian zones (Agnote 2009). - Minor displacement of some dominant or indicator species within any one layer/strata.	ml	h
(b) medium value EVC	EVC = Herb Rich Foothills Forest (D); CMA = North East; Bioregion = Victorian Riverina; VH CLIMATE potential. “Invasive trees such as Celtis, are among the most damaging to the natural ecosystem, as a result of their ability to become structurally dominant.” (Agnote 2009). It out-competes and replaces native shrubs and trees (Agnote 2009). Some of the same species of birds, also feed during the same period on fruit of Camphor Laural. This may significantly enhance the dispersal of Celtis throughout the disturbed, regenerating riparian zones (Agnote 2009). - Major displacement of some dominant/indicator species within a strata/layer (or some dominant species within different layers).	mh	h
(c) low value EVC	EVC = Wet Forest (LC); CMA = Goulburn Broken; Bioregion = Highlands Northern Fall; VH CLIMATE potential. “Invasive trees such as Celtis, are among the most damaging to the natural ecosystem, as a result of their ability to become structurally dominant.” (Agnote 2009). It out-competes and replaces native shrubs and trees (Agnote 2009). Some of the same species of birds, also feed during the same period on fruit of Camphor Laural. This may significantly enhance the dispersal of Celtis throughout the disturbed, regenerating riparian zones (Agnote 2009). - Minor displacement of some dominant or indicator species within any one layer/strata.	ml	h
11. Impact on structure?	“Invasive trees such as Celtis, are among the most damaging to the natural ecosystem, as a result of their ability to become structurally dominant.” (Agnote 2009). It out-competes and replaces native shrubs and trees (Agnote 2009). Some of the same species of birds, also feed during the same period on fruit of Camphor Laural. This may significantly enhance the dispersal of Celtis throughout the disturbed, regenerating riparian zones (Agnote 2009). Displaces all spp within a stata/layer.	h	mh
12. Effect on threatened flora?	Mediterranean Woodlands and Shrublands, Montane vegetation of Mt. Hermon (FLIS 2009). “It rapidly colonises disturbed bushland and can form dense thickets and dominate riparian vegetation – It out-competes and replaces native shrubs and trees (Agnote 2009). No particular mention to threatened species, but has the potential to reduce population sizes of species in habitats it invades and becomes dominant. No specific mention of replacing threatened spp. but potential is high.	m	m
Fauna
13. Effect on threatened fauna?	The fruit of this tree is sweet and edible, and can be eaten raw or cooked (WIKI 2009). No, spines, burrs, thorns (Agnote 2009). Unlikely to have a major effect on threatened fauna species. Except were species are dependant on a particular habitat which is replaced, but no reports of this. Minor effects.	ml	m
14. Effect on non-threatened fauna?	The fruit of this tree is sweet and edible, and can be eaten raw or cooked (WIKI 2009). Unlikely to have a major effect on fauna species. Except were species are dependant on a particular habitat which is replaced, but no reports of this. Minor effects on fauna spp.; minor hazard or reduction in habitat/food/ shelter.	ml	m
15. Benefits fauna?	The fruit of this tree is sweet and edible, and can be eaten raw or cooked (WIKI 2009). A food source. Provides an important alternative food source and/or harbor to desirable species.	ml	mh
16. Injurious to fauna?	No spines, burrs, thorns, toxins (Agnote 2009). No effect.	l	mh
Pest Animal
17. Food source to pests?	The fruit of this tree is sweet and edible, and can be eaten raw or cooked (WIKI 2009). Therefore likely to be a food source to foxes. Supplies food serious pest (eg. rabbits and foxes), but at low levels (eg. foliage).	mh	mh
18. Provides harbor?	Can form dense thickets and dominate riparian vegetation (Agnote 2009). Likely to harbour pests such as bush rabbits. Capacity to harbor rabbits or foxes at low densities or as overnight cover.	mh	mh
Agriculture
19. Impact yield?	“Celtis is an invasive environmental weed and a potential weed of agriculture” (Agnote 2009). Potential impacts unclear, likely to restrict access of livestock to water sources.	mL	m
20. Impact quality?	Invades pine plantations (Blood 2001). Likely to reduce quality of timber due to competition with C. australis. Minor impact on quality of produce (eg < 5% reduction).	ml	mh
21. Affect land value?	No information , but it can be controlled (Agnote 2009).	m	l
22. Change land use?	Can be controlled (Agnote 2009), therefore unlikely to cause a change in land use. Little or no change	l	m
23. Increase harvest costs?	Control would increase harvest costs, especially in forestry (Blood 2001) Minor increase in cost of harvesting – eg slightly more time or labour is required.	ml	mh
24. Disease host/vector?	No pests or diseases are of major concern but twigs may occasionally die from the parasitic fungus which causes witches’ broom (UNFL 2009). Provides host to minor (or common) pests, or diseases.	ml	mh

Invasive

QUESTION	COMMENTS	RATING	CONFIDENCE
Establishment
1. Germination requirements?	Seeds are highly germinable (AANF 2009) but cold and moist stratification probably needed for germination (Blood 2001). Requires natural seasonal disturbances such as seasonal rainfall, spring/summer temperatures for germination.	mh	mh
2. Establishment requirements?	The plant prefers light (sandy) and medium (loamy) soils, requires well-drained soil and can grow in nutritionally poor soil. The plant prefers acid, neutral and basic (alkaline) soils. It cannot grow in the shade. It requires dry or moist soil and can tolerate drought. The Mediterranean climate is especially suitable for the plant (WIKI 2009). Requires more specific requirements to establish (eg. open space or bare ground with access to light and direct rainfall).	ml	mh
3. How much disturbance is required?	Weed in heavily disturbed sites in the Sacramento Valley of California (USDA 2009). Establishes in highly disturbed natural ecosystems (eg. roadsides, wildlife corridors, or areas which have a greater impact by humans such as tourist areas or campsites) or in overgrazed pastures/poorly growing or patchy crops.	ml	mh
Growth/Competitive
4. Life form?	Tree growing up to 20m tall (Agnote 2009) - Other.	l	mh
5. Allelopathic properties?	Some weak allelopathic effects (CABA 2009). Minor properties.	ml	mh
6. Tolerates herb pressure?	Not enough information.	m	l
7. Normal growth rate?	Growth rate: fast (UNFL 2009). Rapid growth rate that will exceed most other species of the same life form.	h	mh
8. Stress tolerance to frost, drought, w/logg, sal. etc?	Aerosol salt tolerance: moderate (UNFL 2009). Water logging causes die back (AANF 2009). Can Tolerate drought (WIKI 2009); Needs minimum rainfall of 500mm (AANF 2009). Very Drought tolerant (PFAF 2009). Tolerates frost (Blood 2001). Tolerant to at least two and susceptible to at least one.	ml	mh
Reproduction
9. Reproductive system	The flowers are hermaphrodite (have both male and female organs) (WIKI 2009). Pollinated by bees (PFAF 2009). Sexual (self and cross-pollination).	ml	mh
10. Number of propagules produced?	Small dark – purple berries (drupes), hang in short clusters (WIKI 2009). Celtis produces thousands of fleshy fruits (Agnote 2009). Above 2000	h	mh
11. Propagule longevity?	The seed can be stored for up to 5 years (PFAF 2009). Greater than 25% of seeds survive 5-10 years in the soil, or lower viability but survive 10-20 years.	ml	mh
12. Reproductive period?	Long living tree (Wiki 2009). Trees can be very long-lived, perhaps to 1000 years (PFAF 2009). Mature plant produces viable propagules for 10 years or more, or species forms self-sustaining monocultures.	h	mh
13. Time to reproductive maturity?	No information.	m	l
Dispersal
14. Number of mechanisms?	Small, dark-purple berries (drupes), 1 cm wide hang in short clusters and are extremely popular with birds and other wildlife (WIKI 2009). It is often planted as an ornamental as it is resistant to air pollution and long-living (WIKI2009). May sucker (Blood 2001). Very light, wind dispersed seeds, or bird dispersed seeds, or has edible fruit that is readily eaten by highly mobile animals.	h	mh
15. How far do they disperse?	Bird dispersed. Likely that at least one seed will be dispersed over 1km.	h	m

References

AANF (2009) Adelaide Advanced Nursery Fact Sheet. Available at http://www.natives.net.au/docs/docs/CeltisAustralisFS.pdf (verified 10/05/2009).

Agnote (2009) NSW Agriculture. Agnote. Available at http://www.dpi.nsw.gov.au/__data/assets/pdf_file/0009/155889/celtis.pdf (verified 10/05/2009).

Blood, K. (2001) Environmental weeds. A field guide for SE Australia. C H Jerram Science publishers.

CABA (2009) Cab Abstracts: Studies on the allelopathic effects of some agroforestry tree crops of Garhwal Himalaya. Bhatt, B. P., Todaria, N. P. (2006).

FLIS (2009) Flowers in Israel. Available at http://www.flowersinisrael.com/Celtisaustralis_page.htm (verified 10/05/2009).

PFAF (2009) Plants for a future. Available at http://www.ibiblio.org/pfaf/cgi-bin/arr_html?Celtis+australis (verified 10/05/2009).

PLNT (2009) Plantnet. Available at http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Celtis~australis (verified 10/05/2009).

UNFL (2009) University of Florida. Forest Service. Available at http://hort.ufl.edu/trees/CELAUSA.pdf (verified 10/05/2009).

USDA (2009) USDA: Agricultural Research service. Available at http://www.ars.usda.gov/research/publications/publications.htm?SEQ_NO_115=203938 (verified 10/05/2009).

WIKI (2009) Wikipedia - Celtis australis. Available at http://en.wikipedia.org/wiki/Celtis_australis (verified 10/05/2009).

Global present distribution data references

Australian Plant Name Index (APNI) http://www.cpbr.gov.au/cgi-bin/apni (26/03/2009).

EIS: Environmental Information System (2006) Parks Victoria. (26/03/2009).

Global Biodiversity Information Facility (GBIF) (2009) Global biodiversity information facility, Available at http://www.gbif.org/ (verified 29 May 2009).

IPMS: Integrated Pest Management System (2006) Department of Primary Industries.

Integrated Taxonomic Information System. (2009) Available at http://www.itis.gov/ (verified 07/05/2009).

Missouri Botanical Gardens (MBG) (2009) w³TROPICOS, Missouri Botanical Gardens Database, Available at http://mobot.mobot.org/W3T/Search/vast.html (viewed 29 May 2009).

United States Department of Agriculture. Agricultural Research Service, National Genetic Resources Program. Germplasm Resources Information Network - (GRIN) [Online Database]. Taxonomy Query. (2009) Available at http://www.ars-grin.gov/cgi-bin/npgs/html/taxgenform.pl (verified 26/03/2009).

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