Bighead knapweed (Centaurea macrocephala)

Present distribution

Scientific name:	Centaurea macrocephala Puschk. ex Willd.
Common name(s):	bighead knapweed

Map showing the present distribution of this weed.

Habitat:

Moist well drained soils in open sunny positions’ (Bodkin 1984). Occurs ‘in high elevation grassy fields and sub-alpine meadows…and grassy
meadows that consist of loams and silt soils’ (North Dakota Dept. of Agriculture 2009). Drought and frost resistant (Bodkin 1984; Dave’s Garden).

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:
Horticulture perennial; pasture dryland; pasture irrigation

Ecological Vegetation Divisions
Grassy/heathy dry forest; lowland forest; high altitude shrubland/woodland; high altitude wetland; alpine treeless; granitic hillslopes; rocky outcrop shrubland; western plains woodland

Colours indicate possibility of Centaurea macrocephala 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?	A perennial plant growing to height and spread of one metre (Bodkin 1986). May form clumps (Backyard Gardener undated). - Low nuisance value. Impedes individual access; unable to walk to waterways.	ml	mh
2. Reduce tourism?	A perennial plant growing to height and spread of one metre. Large (10cm diameter) yellow flowers (Bodkin 1986). Showy flowers may attract birds, bees and butterflies (Backyard Gardener undated). - Minor effects to aesthetics, and/or recreational uses (i.e. aware of weed but not bothered).	ml	mh
3. Injurious to people?	‘Bighead knapweed does not have sharp spines on flower heads [like several other Centaurea species]’ (Roche 1991). Leaves are somewhat lance shaped, with toothed edges and pointed tips, and a rough surface. - Mildly toxic, may cause some physiological issues (e.g. hay fever, minor rashes, minor damage from spines and burrs at certain times of the year.	ml	l
4. Damage to cultural sites?	A perennial plant growing to height of one metre and a spread of one metre. Large (10cm diameter) yellow flowers. Showy yellow flowers may attract birds, bees and butterflies (Backyard Gardener undated; Bodkin 1986). - Moderate visual effects.	ml	m
Abiotic
5. Impact flow?	A perennial plant growing to height of one metre and a spread of one metre (Bodkin 1986). This plant is typically found in high elevation grassy fields and sub-alpine meadows (Roche 1989). C. macrocephala does not grow in riparian zones, nor is it an aquatic plant. Unlikely to affect flows. - Little or negligible affect on water flow.	l	mh
6. Impact water quality?	A perennial plant growing to height of one metre and a spread of one metre (Bodkin 1986). This plant is typically found in high elevation grassy fields and sub-alpine meadows (Roche 1989). C. macrocephala does not grow in riparian zones, nor is it an aquatic plant. Unlikely to affect water quality. - No noticeable effect on dissolved O₂ or light levels.	l	mh
7. Increase soil erosion?	Not enough information.	m	l
8. Reduce biomass?	A perennial plant growing to height of one metre and a spread of one metre (Bodkin 1986). May form clumps (Backyard Gardener undated). Is palatable to livestock (SC 2004). - Impacts on biomass were not determined, although it is unlikely to cause a decrease.	m	l
9. Change fire regime?	A perennial plant growing to height of one metre and a spread of one metre (Bodkin 1986). This plant is typically found in high elevation grassy fields and sub-alpine meadows (Roche 1989). Unlikely to cause an alteration to the fire regime. - Small or negligible effect on fire risk.	l	m
Community Habitat
10. Impact on composition (a) high value EVC	EVC = Swampy Riparian Woodland (V); CMA = North East; Bioregion = Highlands Northern Fall; L CLIMATE potential. A perennial plant growing to height of one metre and a spread of one metre (Bodkin 1986). May form clumps (Backyard Gardener undated). - Minor displacement of some dominant or indicator species within any one layer/strata.	ml	h
(b) medium value EVC	EVC = Warm Temperate Rainforest (R); CMA = East Gippsland; Bioregion = East Gippsland Lowlands; L CLIMATE potential. A perennial plant growing to height of one metre and a spread of one metre (Bodkin 1986). May form clumps (Backyard Gardener undated). - Very little displacement of any indigenous species. Sparse and scattered infestations.	l	h
(c) low value EVC	EVC = Shrubby Dry Forest (LC); CMA =Goulburn Broken; Bioregion = Highlands Northern Fall; M CLIMATE potential. A perennial plant growing to height of one metre and a spread of one metre (Bodkin 1986). May form clumps (Backyard Gardener undated). - Very little displacement of any indigenous species. Sparse and scattered infestations.	l	h
11. Impact on structure?	A perennial plant growing to height of one metre and a spread of one metre (Bodkin 1986). May form clumps (Backyard Gardener undated). - Minor or negligible effect on <20% of the floral strata/layers present; usually only affecting one of the strata.	l	m
12. Effect on threatened flora?	A perennial plant growing to height of one metre and a spread of one metre (Bodkin 1986). May form clumps (Backyard Gardener undated). Impacts on threatened flora have not yet been determined.	mh	l
Fauna
13. Effect on threatened fauna?	Impacts on threatened fauna have not yet been determined.	mh	l
14. Effect on non-threatened fauna?	A perennial plant growing to height of one metre and a spread of one metre (Bodkin 1986). May form clumps (Backyard Gardener undated). Is palatable to livestock (SC 2004). - No fauna affected due to fauna not co-existing within weed area or strata.	l	ml
15. Benefits fauna?	A perennial plant growing to height of one metre and a spread of one metre (Bodkin 1986). May form clumps (Backyard Gardener undated). Is palatable to livestock (SC 2004). - Provides some assistance in either food or shelter to desirable species.	mh	m
16. Injurious to fauna?	Bighead knapweed does not have sharp spines on flower heads [like several other Centaurea species]’ (Roche 1991). Leaves are somewhat lance shaped, with toothed edges and pointed tips, and a rough surface. -Mildly toxic, may cause fauna to lose condition.	ml	m
Pest Animal
17. Food source to pests?	Plants are attractive to bees and butterflies (Backyard Gardener undated). - Provides minimal food for pest species.	l	ml
18. Provides harbor?	A perennial plant growing to height of one metre and a spread of one metre (Bodkin 1986). Size and spread of this plant may create some shelter for small animals. - Doesn’t provide harbour for serious pest species, but may provide for minor pest species.	mh	mh
Agriculture
19. Impact yield?	A perennial plant growing to height of one metre and a spread of one metre (Bodkin 1986). Is palatable to livestock (SC 2004). Palatability to livestock should reduce the impact which this plant will have upon yield. - Little or negligible affect on quantity of yield.	l	m
20. Impact quality?	No evidence suggests that C. macrocephala is an agricultural weed, or contaminant to agricultural produce. - Little or negligible affect on quality of yield.	l	l
21. Affect land value?	Is palatable to livestock (SC 2004). C. macrocephala is not a weed of agriculture, its palatability to livestock should minimise potential impacts which this species may have upon agricultural land. - Little or none.	l	l
22. Change land use?	A perennial plant growing to height of one metre and a spread of one metre (Bodkin 1986). Is palatable to livestock (SC 2004). Control of this species through grazing should pose minimal threat to alterations in the land use. - Little or no change.	l	m
23. Increase harvest costs?	A perennial plant growing to height of one metre and a spread of one metre (Bodkin 1986). Size of C. macrocephala may mean some increased effort for eradication, but as it is palatable to livestock (SC 2004) it is unlikely that harvesting costs/time will increase. - Little or no change.	l	m
24. Disease host/vector?	No evidence suggests that C. macrocephala is a host/vector for diseases.	m	l

Invasive

QUESTION	COMMENTS	RATING	CONFIDENCE
Establishment
1. Germination requirements?	‘Moist well drained soils in open sunny positions’ (Bodkin 1984). - Requires natural seasonal disturbances such as seasonal rainfall, spring/summer temperatures for germination.	mh	l
2. Establishment requirements?	‘Moist well drained soils in open sunny positions’ (Bodkin 1984). Occurs ‘in high elevation grassy fields and sub-alpine meadows…and grassy meadows that consist of loams and silt soils’ (Roche 1991). - Requires more specific requirements to establish (e.g. open space or bare ground with access to light and direct rainfall).	ml	m
3. How much disturbance is required?	‘Moist well drained soils in open sunny positions’ (Bodkin 1984). ‘This plant is typically found in high elevation grassy fields and sub-alpine meadows (Roche 1991). Is often found in high elevation grassy fields and sub-alpine meadows (WS 1998) - Establishes in relatively intact or only minor disturbed natural ecosystems (e.g. grasslands, open woodlands).	mh	mh
Growth/Competitive
4. Life form?	Perennial herb (Bodkin 1984). - Other.	l	h
5. Allelopathic properties?	None described in Rice (1984). - None	l	mh
6. Tolerates herb pressure?	C. macrocephala is palatable to livestock (SC 2004).Tolerant of deer (Backyard Gardener undated). Resistant to rabbits (Heritage Perennials undated). Tolerance to deer and rabbit predation, extent unknown.	m	ml
7. Normal growth rate?	Medium growth rate (Heritage Perennials undated). - Growth rates equal to the same life form.	m	ml
8. Stress tolerance to frost, drought, w/logg, sal. etc?	Drought and frost resistant (Bodkin 1984). Occurs ‘in high elevation grassy fields and sub-alpine meadows…prefers elevations ranging from 2500-2680ft (Roche 1991). Is tolerant of seaside conditions (Backyard Gardener undated). - Tolerant of at least two (drought and frost) and susceptible to at least one (potentially water logging)	ml	ml
Reproduction
9. Reproductive system	Propagation is via seed (Bodkin 1984) and can be propagated through root division (Roche 1991). - Both vegetative and sexual reproduction.	h	mh
10. Number of propagules produced?	‘Each flower head is capable of producing up to 200 seeds (Roche 1991). - Above 2000	h	mh
11. Propagule longevity?	No information.	m	l
12. Reproductive period?	Perennial herb (Bodkin 1984). - Mature plant produces viable propagules for3-10 years.	mh	mh
13. Time to reproductive maturity?	Perennial herb (Bodkin 1984). - 2-5 years to reach sexual maturity or vegetative propagules become separate individuals.	ml	mh
Dispersal
14. Number of mechanisms?	No information.	m	l
15. How far do they disperse?	No information.	m	l

References

Backyard Gardener Centaurea macrocephala fact sheet, available at http://www.backyardgardener.com/plantname/pda_c164.html (verified 25 February 2009).

Bodkin F. (1986) Encyclopaedia Botanica: The Essential Reference Guide to Native and Exotic Plants in Australia. Angus & Robertson.

Heritage Perennials (2000-2009), available at http://www.perennials.com/seeplant.html?item=1.125.100 (verified 25 February 2009).

North Dakota Department of Agriculture Centaurea macrocephala fact sheet, available at http://www.agdepartment.com/noxiousweeds/pdf/Big-headedknapweed.pdf (verified 25 February 2009).

Rice EL. (1984) Allelopathy. Academic Press, Inc. Orlando.

Roche (1991) Bighead knapweed (Centaurea macrocephala Puschk.). Pacific North West Cooperative Extension Publication

WS (1998) Written findings of the Washington State Noxious Weed Control Board (1998) Centaurea macrocephala, available at http://www.nwcb.wa.gov/weed_info/written_findings/CLASS%20A%20PDFs/Centaurea%20macrocephala%201998.pdf (verified 04 March 2009).

SC (2004) Stevens County Noxious Weeds Control Board – Bighead Knapweed. Available at http://www.co.stevens.wa.us/weedboard/PDF_weed/bk.pdf (verified 04 March 2009)

Global present distribution data references

Global Biodiversity Information Facility (GBIF). (2008) Available at http://www.gbif.org/ (verified 25 February 2009).

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

Missouri Botanical Gardens (MBG). w³TROPICOS, Missouri Botanical Gardens Database. (2007) Available at http://mobot.mobot.org/W3T/Search/vast.html (verified 05 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 05 May 2009).

Australian National Herbarium (ANH) Australia’s Virtual Herbarium, Centre for Plant Diversity and Research. (2008) Available at http://www.anbg.gov.au/avh/ (verified 05 May 2009).

Department of Sustainability and Environment (DSE) (2006) Flora information system [CD-ROM], Biodiversity and Natural Resources Section, Viridans Pty Ltd, Bentleigh.

EIS: Environmental Information System (2006) Parks Victoria.

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

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