Ehrharta erecta (panic veldtgrass)
- Summary of Invasiveness
- Taxonomic Tree
- Distribution Table
- History of Introduction and Spread
- Risk of Introduction
- Habitat List
- Biology and Ecology
- Means of Movement and Dispersal
- Economic Impact
- Environmental Impact
- Threatened Species
- Risk and Impact Factors
- Similarities to Other Species/Conditions
- Prevention and Control
- Gaps in Knowledge/Research Needs
- Distribution Maps
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PicturesTop of page
IdentityTop of page
Preferred Scientific Name
- Ehrharta erecta Lam.
Preferred Common Name
- panic veldtgrass
Other Scientific Names
- Ehrharta abyssinica Hochst
- Ehrharta erecta var. abyssinica (Hochst.) Pilg.
- Ehrharta erecta var. erecta (Hochst.) Pilg.
- Ehrharta erecta var. natalensis Stapf.
- Ehrharta panicea Sm.
- Ehrharta paniciformis Nees ex Trin.
- Panicum deflexum Guss. ex Ten.
- Trochera panicea Baill.
Local Common Names
- : ehrharta; Lamarck's erharta; panic veld grass; panic veldgrass; panic veldt-grass; perennial grass
- : zhou fu cao
Summary of InvasivenessTop of page
E. erecta is a grass native to Africa that has been introduced to China, USA, Italy, Australia and New Zealand. Its abilitiy to live in many different habitats, flower and seed throughout the year, germinate rapidly and quickly develop large populations all contribute to its invasiveness. By dominating the ground layer it can restrict the growth and regeneration of native plants, eventually eliminating smaller species.
Taxonomic TreeTop of page
- Domain: Eukaryota
- Kingdom: Plantae
- Phylum: Spermatophyta
- Subphylum: Angiospermae
- Class: Monocotyledonae
- Order: Cyperales
- Family: Poaceae
- Genus: Ehrharta
- Species: Ehrharta erecta
DescriptionTop of page
Modified from Clayton et al. (2013):
Habit: Perennial; caespitose. Culms decumbent; 40–100 cm long; 4–6 -noded; rooting from lower nodes. Leaf-sheath auricles falcate. Ligule an eciliate membrane; 2–7 mm long; entire, or lacerate; truncate, or obtuse. Leaf-blades 4–20 cm long; 2–10(–15) mm wide.
Inflorescence: Inflorescence a panicle.
Panicle open, or contracted; linear, or elliptic; equilateral, or nodding; 6–20 cm long. Primary panicle branches appressed, or ascending; 1–3 -nate; simple. Panicle branches stiff; smooth, or scaberulous.
Spikelets solitary. Fertile spikelets pedicelled. Pedicels filiform; 2–10 mm long.
Fertile Spikelets: Spikelets comprising 2 basal sterile florets; 1 fertile florets; without rhachilla extension. Spikelets oblong; laterally compressed; (3–)4–5.75(–6.8) mm long; breaking up at maturity; disarticulating below each fertile floret. Floret callus glabrous, or pubescent.
Glumes: Glumes persistent; similar; shorter than spikelet; thinner than fertile lemma. Lower glume ovate; 3–3.6 mm long; 0.8 length of upper glume; membranous; 1-keeled; 3(–5) -veined. Lower glume apex obtuse, or acute. Upper glume ovate; 2.5–4.5 mm long; 0.8 length of adjacent fertile lemma; membranous; without keels; 5 -veined. Upper glume apex emarginate, or acute.
Florets: Basal sterile florets similar; barren; without significant palea; attached to and deciduous with the fertile. Lemma of lower sterile floret elliptic; 5.4 mm long; coriaceous; 1-keeled; 5 -veined; smooth, or rugose; rough above; glabrous, or hispidulous; obtuse. Lemma of upper sterile floret elliptic; basally auriculate; 6.5 mm long; 1.2 length of lower sterile floret; coriaceous; smooth, or rugose above; obtuse, or acute. Fertile lemma ovate; 2.5–5.5 mm long; coriaceous; keeled; 5 -veined. Lemma midvein scaberulous. Lemma lateral veins with cross-veins. Lemma apex obtuse. Palea 2 -veined. Palea keels approximate; scaberulous.
Flowers: Lodicules 2; obovate; membranous; 2-toothed; obtuse. Anthers 6; 1.5–2 mm long.
DistributionTop of page
E. erecta is native to a large part of the eastern side of the African continent, from South Africa up to Eritrea and Ethiopia, as well as Yemen. It has been introduced to China, California and Hawaii (USA), Italy, Australia and New Zealand. According to Frey (2005), E. erecta now occurs in California throughout the San Francisco Bay area, in Santa Cruz, San Luis Obispo, Mendocino, Yolo, San Diego, Los Angeles, Ventura, Santa Barbara and on the Farallon Islands.
Distribution TableTop of page
The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.
|Continent/Country/Region||Distribution||Last Reported||Origin||First Reported||Invasive||Reference||Notes|
|China||Present||Introduced||Flora of China, 2013|
|-Yunnan||Present||Introduced||Flora of China, 2013|
|Congo Democratic Republic||Present||Native||USDA-ARS, 2013|
|Mozambique||Present||Native||Launert, 1971||Manica, Mt. Zuira, Tsetsera|
|South Africa||Present||Native||USDA-ARS, 2013||Cape Province, Free State, KwaZulu-Natal, Transvaal|
|Tanzania||Present||Native||Napper, 1965||Forest and forest edges, 4,500 – 8,500 ft.|
|USA||Present||Present based on regional distribution.|
|Italy||Present||Introduced||Ricciardi and Anzalone, 1988|
|-New South Wales||Widespread||Introduced||Invasive||University of Queensland, 2013|
|-Queensland||Present||Introduced||University of Queensland, 2013||South-east|
|-South Australia||Present||Introduced||University of Queensland, 2013||South-east|
|-Tasmania||Present||Introduced||University of Queensland, 2013|
|-Victoria||Widespread||Introduced||Invasive||University of Queensland, 2013|
|-Western Australia||Present||Introduced||University of Queensland, 2013|
|New Zealand||Present||Introduced||Invasive||Edgar and Connor, 2010|
History of Introduction and SpreadTop of page
Stebbins (1985) reported that E. erecta first established as an adventive in northern California in about 1930. The same author observed the spread of the diploid form of E. erecta from an accidental ‘escape’ (in excavated soil) in 1948 into a grove of oaks (Quercus sp.). By around 1965 the species had spread extensively westward, colonising diverse areas, some in hard-packed soil and others in well-drained areas under redwoods (Sequoia sempervirens). According to Frey (2005), E. erecta now occurs throughout the San Francisco Bay area, in Santa Cruz, San Luis Obispo, Mendocino, Yolo, San Diego, Los Angeles, Ventura, Santa Barbara and on the Farallon Islands.
E. erecta was first reported as naturalised in Maui, Hawaii in 1979 by Herbst and Clayton (1988), having apparently escaped from plantings in experimental grass plots at the Hawaii Agricultural Experimental Station on Haleakal.
In the past 10-15 years E. erecta has spread rapidly in New Zealand, especially in the Palmerston North and Wellington areas, where it has become abundant (Edgar and Connor, 2010).
IntroductionsTop of page
|Introduced to||Introduced from||Year||Reason||Introduced by||Established in wild through||References||Notes|
|Natural reproduction||Continuous restocking|
|Australia||South Africa||1910||Seed trade (pathway cause)||Yes||No||Australia’s Virtual Herbarium (2013); Jessop et al. (2006); McIntyre and Ladiges (1985); Royal Botanic Gardens Sydney (2004); Royal Botanic Gardens Sydney (2013)||Accidental spread in garden soil or birdseed?|
|New Zealand||Africa||Before 1943||Seed trade (pathway cause)||Yes||No||Ogle (1988)||Accidental spread in bird seed? Spread rapidly around Wellington since the early 1970s|
Risk of IntroductionTop of page
In Australia, McIntyre and Ladiges (1985) considered it plausible that E. erecta arrived in garden soil imported from South Africa; Jessop et al. (2005) suggested it was introduced to Victoria in 1950 in birdseed. Ogle (1988) also thought it may have arrived in New Zealand in imported birdseed.
In theory, border inspections of seeds and other products being imported into a country ought to reduce the likelihood of the introduction of E. erecta into other countries, but its occurrence as a garden weed increases the chances of seed being transferred on contaminated footwear, clothing or baggage.
Once present in a country, E. erecta is able to spread quickly, initially in gardens and around towns (McIntyre and Ladiges, 1985; Ogle, 1988), and later into native bush areas. Rapid spread within a country is possible because seeds can be carried for short distances by wind or water and for longer distance by birds (Ogle, 1988), by vehicles or on footwear. Sigg (1996) reported that in one Californian forest, E. erecta is found along 'many miles of single-track hiking trails.'
HabitatTop of page
In its native Africa, Launert (1971) described the habitat of E. erecta as ‘mainly in forest shade in places with open canopies or in clearings, but also in disturbed areas and on hillsides, occasionally even on coastal sands.’
E. erecta has been introduced and has become naturalised and invasive in California, Hawaii, Australia and New Zealand. Areas invaded are apparently of above-average moisture, although once established it can move into drier, more open areas. ‘In contrast to all other spp. of the genus, E. erecta is adapted to a wide range of edaphic conditions which explains the great variability of the species’ (Launert, 1971).
In California it is often found in scrub, grassland, woodland disturbed areas, urban areas and turf, riparian and coastal places, especially on stabilised dunes, and in shaded habitats, including moist wildlands (Frey, 2005; Cal-IPC, 2013). Sigg (1996) stressed its wide tolerance range in California: ‘on the coast, it grows on hot, dry banks or in deep shade; it grows in pure sand; in heavy soils; in soils that stay waterlogged for extended periods (thus a threat to wetlands); in thin, rocky soils; and in cracks in vertical rock faces.’
In Australia E. erecta grows in grassy woodlands, forest, heathland, river banks and coastal areas (Weeds of Australia, 2013).
In New Zealand it grows particularly well in low fertility, sandy, loess-based soils, especially in bases of hedges, untended shrubberies, and on banks. It also grows well in open cultivated ground and can even establish and persist in mown lawns. E. erecta grows readily in the heavier clay soils of Wellington city and tolerates both dry and damp conditions. It is able to grow well in very shady conditions which other adventive grasses cannot tolerate (Ogle, 1988). Edgar and Connor (2010) described its habitat in New Zealand as stabilised sand dunes, waste places and ruderal habitats. The same authors added that in the past 10-15 years E. erecta has spread rapidly, especially in the Palmerston North and Wellington areas, where it has become abundant.
E. erecta performs well in urban environments, such as Wellington and San Francisco (Sigg, 1996).
Habitat ListTop of page
|Terrestrial – Managed||Disturbed areas||Present, no further details|
|Urban / peri-urban areas||Present, no further details|
|Terrestrial ‑ Natural / Semi-natural||Natural forests||Present, no further details|
|Natural grasslands||Present, no further details|
|Riverbanks||Present, no further details|
|Rocky areas / lava flows||Present, no further details|
|Coastal areas||Present, no further details|
|Coastal dunes||Present, no further details|
Biology and EcologyTop of page
The chromosome number is recorded as 2n=48 (Guo and Song, 2005).
Stebbins (1985) planted paired plots of the diploid and a colchicine-induced autotetraploid, and reported that the diploid spread extensively: the autotetraploid was less aggressive and had not invaded different habitats.
Although E. erecta can reproduce vegetatively by rooting at the nodes of its decumbent flower stems (Frey, 2005), it can produce copious seeds at any time of the year if moisture conditions allow (Ogle, 1998).
Physiology and Phenology
In Victoria, Australia, McIntyre and Ladiges (1985) found that seedling emergence began in autumn (May), following summer drought and that seedling density was as high as almost 1200 seedlings m-2 at one site. The number of seeds in the soil declined dramatically between March and May as seedlings emerged. The same authors found that fresh seeds had some innate dormancy which was broken by dry storage at room temperature for 11 months and that germination was further accelerated by removal of the lemmas from the caryopses.
McIntyre and Ladiges (1985) grew plants of E. erecta under different levels of shade and found that plants in 0.6 % of full daylight declined in weight and suffered high mortality. However, those at 13.6 % of full daylight did not have significantly lower dry weight than those in full daylight, although they had a more erect growth form, greater extension, decreased root/shoot ratio and expanded leaf areas.
Plants can produce seeds throughout the year if soil moisture conditions are adequate (Ogle, 1988; Muyt, 2001). Seed germination rates are high, recorded as 99% within 11 months in Australia (McIntyre and Ladiges, 1985). Frey (2005) reported that plants can set seed when less than 8 cm tall and that they can thrive under native vegetation.
Population Size and Structure
Seedling density can exceed 1150 m-2 (McIntyre and Ladiges, 1985). Gluesenkamp (2004) wrote that in California E. erecta forms robust monospecific stands under full sun or in as little as 2.5 % of daylight, quoting Haubensak and Smyth (2000). Weeds of Australia (2013) also stated that it develops large populations quickly, dominating the ground layer in native vegetation.
E. erecta has been found under a canopy of Leptospermum laevigatum in Australia (McIntyre and Ladiges, 1985) and in low stature scrub dominated by Coprosmapropinqua and Muehlenbeckia complexa around Wellington in New Zealand (Ogle, 1988).
E. erecta grows readily in the heavier clay soils of Wellington, New Zealand, and tolerates both dry and damp conditions. It is able to grow well in very shady conditions which other adventive grasses cannot tolerate (Ogle, 1988).
Means of Movement and DispersalTop of page
Natural Dispersal (Non-Biotic)
Ogle (1988) suggested that wind and water were responsible for local spread of E. erecta in New Zealand.
Vector Transmission (Biotic)
Seeds of E. erecta can be carried to new sites in soil on deer hooves. Starlings have been suggested as responsible for movement of seeds to offshore island (Ogle, 1988). Cal-IPC (2013) suggested that mowing can aid establishment and dispersal.
E. erecta seeds may be carried as contaminants in potted plants (Gluesenkamp, 2004), in soil (including garden soil) attached to shoes and on clothing and equipment. Others too have mentioned its inadvertent movement in garden soil (McIntyre and Ladiges, 1985; Ogle, 1988).
Economic ImpactTop of page
It does not appear to seriously affect any farming enterprises.
Environmental ImpactTop of page
Impact on Habitats
The impacts of E. erecta on natural habitats have been described in California (Frey, 2005), New Zealand (Ogle, 1988) and Australia (Weeds of Australia, 2013). In California it is considered a ‘moderate’ threat (Sigg, 1996), and it has invaded moist wildlands, urban areas, riparian and coastal habitats, especially coastal dunes (Cal-IPC, 2013). In such places E. erecta can dramatically change plant community composition, alter fire potential and increase organic matter accumulation (Frey, 2005).
In New Zealand, E. erecta is abundant and out-competing native species in some areas of low stature scrub, and it has found its way to offshore islands (Ogle, 1988). The same author predicted that it would become ‘an increasingly common weed in a wide variety of ungrazed sites through much of lowland New Zealand.’
In Australia it is found in grassy woodlands, forests, heathland, riverbanks and coastal environments, often invading undisturbed natural vegetation (Weeds of Australia, 2013). There it rapidly dominates the ground layer in native vegetation, restricting the growth and regeneration of indigenous plants and eventually eliminating smaller native species.
Impact on Biodiversity
E. erecta has the potential to swamp lower growing native species in invaded habitats, as well as increasing the fire risk and adding to the accumulation of organic matter.
Threatened SpeciesTop of page
|Threatened Species||Conservation Status||Where Threatened||Mechanism||References||Notes|
|Speyeria callippe callippe (callippe silverspot butterfly)||USA ESA listing as endangered species USA ESA listing as endangered species||California||Ecosystem change / habitat alteration||US Fish and Wildlife Service, 2009|
Risk and Impact FactorsTop of page Invasiveness
- Proved invasive outside its native range
- Has a broad native range
- Highly adaptable to different environments
- Pioneering in disturbed areas
- Benefits from human association (i.e. it is a human commensal)
- Long lived
- Fast growing
- Has high reproductive potential
- Has propagules that can remain viable for more than one year
- Reproduces asexually
- Has high genetic variability
- Ecosystem change/ habitat alteration
- Highly likely to be transported internationally accidentally
- Difficult to identify/detect in the field
UsesTop of page
Mulroy et al. (1992) and Pickart (2000), both quoted in Frey (2005), reported that E. erecta had been used for forage and erosion control in California and Australia. NSWDPI (2013) suggests that it has been used in New South Wales, Australia, as a pasture and soil stabilisation species. It was possibly imported into New Zealand in birdseed (Ogle, 1988) or as a potentially useful turf species (Radcliffe and Dale, 1964). However, the adverse effects of its introduction outweigh any economic value it may bring.
Similarities to Other Species/ConditionsTop of page
When not flowering, E. erecta resembles the New Zealand and Australian native grass Microlaena stipoides, but is softer in texture, more yellow-green, and is easier to pull from the soil (Ogle, 1988; Muyt, 2001).
Launert (1971) wrote that ‘in contrast to all other spp. of the genus, E. erecta is adapted to a wide range of edaphic conditions which explains the great variability of the species. The distinguishing characters between E. erecta and E. abyssinica given by various workers in the past break down completely if one tries to apply them to the large number of specimens which are now available from all parts of Africa. O. Stapf (loc. cit.) had already regarded the East African plants as being “a slightly different form” of E. erecta.’
Prevention and ControlTop of page
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.
For most people, E. erecta is ‘just another grass’ and it has few obvious distinguishing characteristics, so that raising public awareness of the dangers it possesses would probably not be very effective. However, raising awareness of its adverse effects with those responsible for upkeep of roads, footpaths and parks and reserves could be beneficial.
Frey (2005) contemplated a ‘scorched earth’ policy for eradication of E. erecta and related species of Ehrharta. Managing (i.e. destroying) small infestations and preventing fresh invasion are preferable and more economical and practical than killing large established infestations. Large scale eradication would be very damaging to any environment and it would be next to impossible to kill every last seed and prevent a fresh invasion of a cleared area.
In Australia, Muyt (2001) reported that plants are easy to dig out, but care must be taken to remove all rhizome material and to dispose of it safely. He also wrote that hot fires will destroy mature plants and stimulate seed germination, but seedlings and any regrowth must be controlled within 4 to 6 weeks. Frey (2005) described hand pulling or digging as successful but time consuming for short-term control; however, soil disturbance may encourage germination of more seeds. Also, by the time E. erecta is recognised in the field is may already have gone through several generations of plants, making mechanical control difficult.
Since the seeds do not appear to have any long-term dormancy, repeated cultivation may eventually deplete the soil seed bank, but this would not be practical in areas of native vegetation. One technique described by Frey (2005) is to cover the ground with black landscape fabric and rice straw 15 cm deep, which was reported as being effective in the short term. Frey (2005) also commented on the use of a gas or vapour flame torch for locally containing plants and wrote that it works better on seedlings than on mature plants. Again, this method would not usually be suitable in areas of native vegetation, or when there was any risk of starting fires.
When moving machinery from affected areas to those where E. erecta does not yet occur, care must be taken that no seed is carried from place to place. The same applies to footwear and sports equipment.
Biological control is not commonly used for grass species, because of their close affinity to many very useful species. However, Frey (2005) mentioned the fungal pathogen Uredo ehrhartae-calycinae found on the related E. calaycina in South Africa, but this has not been evaluated for its effectiveness.
Non-selective or grass-selective herbicides give good control of E. erecta, but treatment must be vigorously followed up with further applications to kill new seedlings or regrowth from mature plants (Muyt, 2001). Both glyphosate (non-selective) and fluazifop-butyl (which selectively kills grasses but not broad-leaved species) have been used for killing E. erecta plants, although results with using fluazifop-butyl have been variable.
The reports of management programs for species of Ehrharta mentioned in Frey (2005) mostly deal with improving herbicidal control of the species, or with using non-chemical methods like manual removal or covering with light-proof material. Long-term effective management has yet to be properly tested.
Control by Utilization
Ogle (1988) observed that ‘grazing by livestock seems to prevent its establishment, perhaps because young plants are more easily pulled up than other pasture grasses.’
Frey (2005) claimed that the potential for restoration of sites invaded by species of Ehrharta is ‘medium to high’, provided that funds and resources for ongoing intense control and maintenance are sufficient. He quoted the report by Pickard (2000) of ‘sufficiently’ successful restoration of native dune scrub in California, USA, after invasion by the related E. calycina, but stressed the need for continuous monitoring and control of new invading plants for several years.
Gaps in Knowledge/Research NeedsTop of page
The very serious invasive potential of E. erecta has only been recognized relatively recently and it is as yet too soon to know just how damaging this weed could be, although the signs are ominous. It does not appear to seriously affect any farming enterprises, and in any case its growth is apparently restricted in grazed pasture. However it does seem to create serious problems in native environments, especially in coastal areas. Much remains to be discovered about it. More information on its seeds would be useful, especially in relation to dormancy enforced by burial of cover by vegetation or mulches. Above all there is a major need to determine how best to prevent its spread to new areas and how best to restore invaded sites.
ReferencesTop of page
Cal-IPC (California Invasive Plant Council), 2013. California Invasive Plants Council. Berkeley, California, USA: California Invasive Plant Council. http://www.cal-ipc.org/
Clayton WD, Vorontsova MS, Harman KT, Williamson H, 2013. GrassBase - The Online World Grass Flora. http://www.kew.org/data/grasses-db/
Flora of China, 2013. Flora of China. http://www.efloras.org/
Frey M, 2005. Element Stewardship Abstract for Ehrharta spp. Thunb. Arlington, Virginia, USA: The Nature Conservancy. http://www.imapinvasives.org/GIST/ESA/esapages/ehrhcaly.html
Gluesenkamp D, 2004. ACR's Bolinas Lagoon Preserve as a test area for regional conservation: Eliminating Ehrharta. The Ardeid: Research and Resource Management at Audubon Canyon Ranch:6-9. http://www.egret.org/pdfs/Ardeid2004.pdf
Guo YaLong, Ge Song, 2005. Molecular phylogeny of Oryzeae (Poaceae) based on DNA sequences from chloroplast, mitochondrial, and nuclear genomes. American Journal of Botany, 92(9):1548-1558. http://www.amjbot.org/
Haubensak K, Smyth A, 1999. Ehrharta erects. Species assessment prepared for Channel Islands National Park.
Herbst DR, Clayton WD, 1998. Notes on the grasses of Hawaii: new records, corrections, and name changes. Part 1: Articles. Notes on the grasses of Hawaii, 55:17-39. [Records of the Hawaii Biological Survey for 1997.]
Jessop J, Dashorst GRM, James FM, 2006. Grasses of South Australia: an illustrated guide to the native and introduced species. Kent Town, Australia: Wakefield Press, 554.
Launert E, 1971. Gramineae. In: Fernandes A, Launert E, Wild H, eds. Flora Zambesiaca, Vol. 10, Part 1. London, UK: Flora Zambesiaca Management Committee.
Mulroy TW, Dungan ML, Tich RE, Mayerle BC, 1992. Wildland weed control in sensitive natural communities: Vandenberg Air Force Base, California. In: Proceedings of the 44th California Weed Conference, January 22, 1992, Fremont, CA. 166-180.
Muyt A, 2001. Bush invaders of South-East Australia: a guide to the identification and control of environmental weeds found in South-East Australia. Meredith, Australia: R.G. and F.J. Richardson, xvi + 304 pp.
NSWDPI, 2013. New South Wales Weed Risk Management System. NSW Department of Primary Industries: Agriculture. New South Wales, Australia. http://www.dpi.nsw.gov.au/agriculture
Ogle C, 1988. Veld grass (Ehrharta erecta) has come to stay. Bull. Wellington Bot. Soc., 44:8-15.
Pickart AJ, 2000. Ehrharta calycina, Ehrharta erecta, and Ehrharta longiflora in: (eds.) 2000. Invasive Plants of California's Wildlands. In: Invasive Plants of California's Wildlands [ed. by Bossard, C. C. \Randall, J. M. \Hoshovsky, M. C.]. Berkeley, California, USA: University of California Press, 164-170.
Radcliffe J, Dale WR, 1964. Ehrharta erecta - a possible turf species for coastal sands. New Zealand Institute for Turf Culture Newsletter, 30:6-7.
Royal Botanic Gardens Sydney, 2013. Australia’s Virtual Herbarium. Sydney, Australia: Royal Botanic Gardens. http://avh.chah.org.au/
Sigg J, 1996. Ehrharta erecta: sneak attack in the making? CalEPPC News, Summer/Fall:8-9. http://www.cal-ipc.org/resources/news/pdf/newsletters886.pdf
Stebbins GL, 1985. Polyploidy, hybridization, and the invasion of new habitats. Annals of the Missouri Botanical Garden, 72:824-832.
University of Queensland, 2013. Weeds of Australia, Biosecurity Queensland edition. Queensland, Australia. http://keyserver.lucidcentral.org/weeds/
USDA-ARS, 2013. Germplasm Resources Information Network (GRIN). Online Database. Beltsville, Maryland, USA: National Germplasm Resources Laboratory. https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomysearch.aspx
USDA-NRCS, 2013. The PLANTS Database. Baton Rouge, USA: National Plant Data Center. http://plants.usda.gov/
ContributorsTop of page
20/05/13: Original text by:
Ian Popay, consultant, New Zealand, with the support of Landcare Research.
Distribution MapsTop of page
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