Blue sedge (Carex flacca)

Present distribution

Scientific name:	Carex flacca (Schreber)
Common name(s):	Glaucous sedge, Blue sedge

Map showing the present distribution of this weed.

Habitat:

Open grassland, Nine populations of Carex flacca Schreb., collected from sites which vary widely in their liability to soil flooding, While usually found on dry soils, it is frequent in damp rich-base marshy places, but only where the soil is oxidising and not waterlogged in summer. Some of the marshes of this type near the coast may be somewhat brackish. Usually in wetlands and often invasive in poorly drained pasture or pasture bordering wetlands. Tolerant of heavy shade and full sun. Often favouring soils overlying calcareous or other base-rich substrates.

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; water

Ecological Vegetation Divisions
Swampy scrub; treed swampy wetland; foothills forest; forby forest; high altitude wetland; alpine treeless; basalt grassland; alluvial plains grassland; riverine woodland/forest; saline wetland

Colours indicate possibility of Carex flacca infesting these areas.

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

map showing the potential distribution of blue sedge

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

Impact

QUESTION	COMMENTS	RATING	CONFIDENCE
Social
1. Restrict human access?	Loosely tufted, to 60 cm, with rounded angles or subterete, smooth. (Interactive Flora of NW Europe, 2008) Low nuisance value. Impedes individual access; unable to walk to waterways.	ml	mh
2. Reduce tourism?	Loosely tufted, to 60 cm, with rounded angles or subterete, smooth. (Interactive Flora of NW Europe, 2008) Some recreational uses affected.	mh	mh
3. Injurious to people?	Stems trigonous but glabrous, but the margins and keel of the leaves are scabrous (Erteeb & Sherif 1985). Edges of the leaves may cut if hands are drawn up the plant. may cause some physiological issues	ml	mh
4. Damage to cultural sites?	The rizome is a much-branched organ giving rise to numerous shoots. It lies about 3-8 cm. below the surface, often in the surface litter. The roots do not penetrate to more than about 15 cm. below the surface, and are usually found in the top 10 cm. (Taylor F J 1956) Moderate visual effect.	ml	mh
Abiotic
5. Impact flow?	C. flacca is well established on wet flats in some higher rainfall districts, forming dense, low, blue-green swards, at times of considerable area. (Flora of NZ 2008) Major impact on either surface and subsurface flow	mh	mh
6. Impact water quality?	No info	m	l
7. Increase soil erosion?	C. flacca is well established on wet flats in some higher rainfall districts, forming dense, low, blue-green swards, at times of considerable area. (Flora of NZ 2008) decreases the probability of soil erosion.	l	mh
8. Reduce biomass?	Tansley and Adamson (1925) noted that in the fenced area at Downley Bottom Carex flacca increased in abundance at first due to decreased rabbit pressure, but then declined as a result of competition from the grasses. (Taylor F J 1956) Direct replacement of biomass by invader.	ml	mh
9. Change fire regime?	No information available	m	l
Community Habitat
10. Impact on composition (a) high value EVC	EVC = Plains Swampy Woodland (E); CMA = Glenelg Hopkins; Bioregion = Victorian Volcanic Plain; VH CLIMATE potential C. flacca is well established on wet flats in some higher rainfall districts, forming dense, low, blue-green swards, at times of considerable area. (Flora of NZ 2008) Monoculture within a specific layer;	h	h
(b) medium value EVC	EVC = Damp Heathland/Damp Heathy Woodland Mosaic (D); CMA = Glenelg Hopkins; Bioregion = Glenelg Plain; VH CLIMATE potential. C. flacca is well established on wet flats in some higher rainfall districts, forming dense, low, blue-green swards, at times of considerable area. (Flora of NZ 2008) Monoculture within a specific layer;	h	h
(c) low value EVC	EVC = Wet Heathland (LC); CMA = Glenelg Hopkins; Bioregion = Glenelg Plain; VH CLIMATE potential C. flacca is well established on wet flats in some higher rainfall districts, forming dense, low, blue-green swards, at times of considerable area. (Flora of NZ 2008) Monoculture within a specific layer;	h	h
11. Impact on structure?	C. flacca is well established on wet flats in some higher rainfall districts, forming dense, low, blue-green swards, at times of considerable area. (Flora of NZ 2008) Major effects on all layers. Forms monoculture	h	mh
12. Effect on threatened flora?	C. flacca is well established on wet flats in some higher rainfall districts, forming dense, low, blue-green swards, at times of considerable area. (Flora of NZ 2008) Any population of Bioregional Priority 1A* spp is reduced, or any population of a VROT spp is replaced	mh	mh
Fauna
13. Effect on threatened fauna?	C. flacca is well established on wet flats in some higher rainfall districts, forming dense, low, blue-green swards, at times of considerable area. (Flora of NZ 2008) Reduction in habitat for threatened spp, leading to reduction in numbers of individuals, but NOT to local extinction.	mh	mh
14. Effect on non-threatened fauna?	C. flacca is well established on wet flats in some higher rainfall districts, forming dense, low, blue-green swards, at times of considerable area. (Flora of NZ 2008) Reduction in habitat for fauna spp., leading to reduction in numbers of individuals, but NOT to local extinction.	mh	mh
15. Benefits fauna?	C. flacca is well established on wet flats in some higher rainfall districts, forming dense, low, blue-green swards, at times of considerable area. (Flora of NZ 2008) Occasionally eaten by sheep, cattle and rabbits, especially in spring and early summer. (Taylor F J 1956) Provides some assistance in either food or shelter to desirable species.	mh	mh
16. Injurious to fauna?	Stems trigonous but glabrous, but the margins and keel of the leaves are scabrous (Erteeb & Sherif 1985). Edges of the leaves may cut if hands are drawn up the plant. Spines, burrs or toxic properties to fauna at certain times of the year.	mh	mh
Pest Animal
17. Food source to pests?	Occasionally eaten by sheep, cattle and rabbits, especially in spring and early summer. Tansley and Adamson (1925) noted that in the fenced area at Downley Bottom Carex flacca increased in abundance at first due to decreased rabbit pressure, but then declined as a result of competition from the grasses. (Taylor F J 1956) Supplies food serious pest (eg. rabbits and foxes), but at low levels (eg. foliage).	mh	mh
18. Provides harbor?	C. flacca is well established on wet flats in some higher rainfall districts, forming dense, low, blue-green swards, at times of considerable area. (Flora of NZ 2008) Capacity to provide harbor and permanent warrens for foxes and rabbits throughout the year.	h	mh
Agriculture
19. Impact yield?	C. flacca is well established on wet flats in some higher rainfall districts, forming dense, low, blue-green swards, at times of considerable area. (Flora of NZ 2008). Little affected by grazing in open grassland. Tansley and Adamson found that on Heyshott down, Carex flacca was the most abundant plant after mosses in a severely rabbit-eaten area. (Taylor F J 1956). Major impact on quality of produce (eg 5-20%).	mh	mh
20. Impact quality?	No information available.	m	l
21. Affect land value?	No information available.	m	l
22. Change land use?	No information available.	m	l
23. Increase harvest costs?	No information available.	m	l
24. Disease host/vector?	No information available.	m	l

Invasive

QUESTION	COMMENTS	RATING	CONFIDENCE
Establishment
1. Germination requirements?	Germination of the seeds takes place in spring and early summer. (Taylor F J 1956 ) Requires natural seasonal disturbances such as seasonal rainfall, spring/summer temperatures for germination	mh	mh
2. Establishment requirements?	Usually in wetlands and often invasive in poorly drained pasture or pasture bordering wetlands. Tolerant of heavy shade and full sun. Often favouring soils overlying calcareous or other base-rich substrates (New Zealand Plant Conservation, 2008) Can establish without additional factors.	h	mh
3. How much disturbance is required?	Most of the communities in which Carex flacca occurs are closed, and it can only invade the more open communities (Taylor F J 1956) Establishes in relatively intact or only minor disturbed natural ecosystems	mh	mh
Growth/Competitive
4. Life form?	Perennial herb. Rhizome long creeping (Erteeb & Sherif 1985) and with long subterranean stolons (Kukkonen 1998). Geophyte	ml	mh
5. Allelopathic properties?	None	l	mh
6. Tolerates herb pressure?	Little affected by grazing in open grassland. Tansley and Adamson found that on Heyshott down, Carex flacca was the most abundant plant after mosses in a severely rabbit-eaten area. (Taylor F J 1956) Consumed but non-preferred	mh	mh
7. Normal growth rate?	Tansley and Adamson (1925) noted that in the fenced area at Downley Bottom Carex flacca increased in abundance at first due to decreased rabbit pressure, but then declined as a result of competition from the grasses. (Taylor F J 1956) Growth rate equal to the same life form	m	mh
8. Stress tolerance to frost, drought, w/logg, sal. etc?	Nine populations of Carex flacca Schreb., collected from sites which vary widely in their liability to soil flooding, were grown on an experimental soil with free drainage, transient flooding or continuous flooding for 26 weeks. Although the flooding treatments resulted in low redox potentials and high concentrations of reduced iron and manganese in the soil, the growth of C. flacca plants was little affected by flooding. (Heathcote, C.A et al 1986) Drought tolerant once established. Spreads slowly by rhizomes. (North creek nurseries) Very resistant to drought which may reduce the stature of the plants, but they can still set seed. Frost has little effect, though a severe frost which reaches the rhizome may result in death. (Taylor F J 1956) While usually found on dry soils, it is frequent in damp rich-base marshy places, but only where the soil is oxidizing and not waterlogged in summer. Some of the marshes of this type near the coast may be somewhat brackish. (Taylor F J 1956) Highly resistant to at least two of drought, frost, fire, waterlogging, and salinity not susceptible to more than one	h	mh
Reproduction
9. Reproductive system	Seed and Rhizome (New Zealand Plant Conservation, 2008) Both vegetative and sexual reproduction	h	h
10. Number of propagules produced?	Unknown	m	l
11. Propagule longevity?	After-ripening of the nuts is essential. Fruits collected in summer will not germinate for 9-12 months. After this period they remain viable for 5 years. (Taylor F J 1956) Greater than 25% of seeds survive 5 years and vegetatively reproduces.	l	mh
12. Reproductive period?	The shoot may live several years but flowers only in the first year. (Taylor F J 1956). Unknown.	m	l
13. Time to reproductive maturity?	Seedlings do not flower for at least the first two years, though a rizome is developed towards the end of the first year. (Taylor F J 1956) Produces propagules between 1-2 years after germination, and vegetative propagules become separate individuals between 1-2 years.	mh	mh
Dispersal
14. Number of mechanisms?	The utricle is liberated from the fruit stalk as a whole, the nut being liberated by decay of the utricle. Dispersal of the utricle is by wind, though being relatively heavy (mean weight of 100-2.8 mg) and without wings, it is not carried far. The utricles are buoyant and remain floating on water for 2.5-3 weeks. (Taylor F J 1956) Dispersed endozoically by ungulates grazing on dry dune meadows (Leck & Schutz 2005). Has edible fruit that is readily eaten by highly mobile animals.	h	mh
15. How far do they disperse?	The utricle is liberated from the fruit stalk as a whole, the nut being liberated by decay of the utricle. Dispersal of the utricle is by wind, though being relatively heavy (mean weight of 100-2.8 mg) and without wings, it is not carried far. The utricles are buoyant and remain floating on water for 2.5-3 weeks. (Taylor F J 1956) Very likely that at least one propagule will disperse greater one kilometre.	h	mh

References

Erteeb FB, Sherif AS. 1985. Cyperaceae. In: Jafri SMH, El-Gadi A, eds. Flora of Libya, Vol. 119-120. Tripoli: Faculty of Sciences, 1–46.

Flora of New Zealand. Name search Available at http://nzflora.landcareresearch.co.nz/default.aspx?NavControl=search&selected=NameSearch (verified 12/05/08)

Heathcote CA, Davies MS and Etherrington, JR Phenotypic flexibility of Carex flacca Schreb. Tolerances of soil flooding by populations from contrasting habitats New Phytology (1987) 105, 381-391

Interactive Flora of NW Europe, Taxonomic scope. Available at http://ip30.eti.uva.nl/bis/flora.php?menuentry=inleiding (verified 12/05/08)

New Zealand Plant Conservation Network, Naturalised Plants. Available at http://www.nzpcn.org.nz/exotic_plant_life_and_weeds/ (verified 13/05/08)

North Creek Nurseries Available at http://www.northcreeknurseries.com/index.cfm (verified 12/05/08)

Taylor FJ 1956, Carex Flacca Schreb, Journal of Ecology, Vol: Vol. 44, Issue: No. 1, Jan 1956, Pages: 281-290

Global present distribution data references

Australian National Herbarium (ANH) (2008) Australia’s Virtual Herbarium, Australian National Herbarium, Centre for Plant Diversity and Research, Available at http://www.anbg.gov.au/avh/ (verified7/5/08).

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

Global Biodiversity Information Facility (GBIF) (2008) Global biodiversity information facility, Available at http://www.gbif.org/ (verified 15/5/08).

Missouri Botanical Gardens (MBG) (2008) w³TROPICOS, Missouri Botanical Gardens Database, Available at http://mobot.mobot.org/W3T/Search/vast.html (viewed 15/5/08).

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