Invasive Species Compendium

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Datasheet

Asparagus densiflorus
(asparagus fern)

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Datasheet

Asparagus densiflorus (asparagus fern)

Summary

  • Last modified
  • 14 November 2018
  • Datasheet Type(s)
  • Invasive Species
  • Host Plant
  • Preferred Scientific Name
  • Asparagus densiflorus
  • Preferred Common Name
  • asparagus fern
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Monocotyledonae
  • Summary of Invasiveness
  • A. densiflorus is a spiny perennial plant, commonly found in savanna thickets in its native environment in eastern Africa and South Africa. It has been widely introduced globally as an ornamental and has subseq...

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Identity

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Preferred Scientific Name

  • Asparagus densiflorus (Kunth) Jessop (1966)

Preferred Common Name

  • asparagus fern

Other Scientific Names

  • Asparagopsis densiflora Kunth (1850)
  • Asparagus aethiopicus L. (1767)
  • Asparagus myriocladus BAK.
  • Asparagus sprengeri Regel (1890)
  • Protasparagus densiflorus (Kunth) Oberm (1983)

International Common Names

  • English: bushy asparagus; coarse asparagus fern; Myer’s asparagus; regal fern; smilax; Sprenger asparagus
  • French: asperge de Sprenger

Local Common Names

  • Australia: fern asparagus; Sprengeris fern
  • Germany: Zier- Spargel
  • Ghana: badji badji; gbadgi gbadgi
  • Netherlands: asperge, hang-
  • USA: Sprenger's asparagus fern

EPPO code

  • ASPSP (Asparagus densiflorus)

Summary of Invasiveness

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A. densiflorus is a spiny perennial plant, commonly found in savanna thickets in its native environment in eastern Africa and South Africa. It has been widely introduced globally as an ornamental and has subsequently naturalised and become a problem in a number of countries, including the USA and Australia. The plant forms dense spiny mats, up to 2 m high in light and sandy soils, suppressing other ground flora and depleting the soil of nutrients and moisture. It may quickly invade disturbed sites in open sun or partial shade and can become a threat in coastal habitats, along river banks and in low fertility soils. It is among the most abundant invasive ornamental weeds of sandy beachfronts in Queensland, Australia and threatens natural vegetation on Lord Howe Island, Norfolk Island and a number of other islands in the Pacific Ocean. The risk assessment score for this plant in Australia is 3 (‘requiring evaluation’) and for the Pacific Islands it has a high score of 15. In Florida, USA it has been reported as displacing native ground cover, understory shrubs and the native wild coffee species Psychotria nervosa. It is also of sufficient concern for it to have been recommended for voluntary withdrawal from sale within the state (Wirth et al., 2004). In Hawaii, USA it is spreading along roadsides and invading secondary forest (PIER, 2008).

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Monocotyledonae
  •                     Order: Liliales
  •                         Family: Liliaceae
  •                             Genus: Asparagus
  •                                 Species: Asparagus densiflorus

Notes on Taxonomy and Nomenclature

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The genus Asparagus has sometimes been attributed to its own family Asparagaceae, but is now generally included in Liliaceae. Missouri Botanical Garden (2008) suggests that the correct name for this species is now Protasparagus densiflorus (Kunth) Oberm., but as this name is not yet widely accepted and many databases do not recognise it, the more commonly recognised name Asparagus densiflorus will be used for this datasheet. Also included will be information based on a number of synonyms, especially A. aethiopicus and A. sprengeri, although some sources insist that A. aethiopicus is not strictly synonymous with A. densiflorus, and the latter continues to be used especially in the horticultural trade, corresponding to the cultivar cv. ‘Sprengeri’ and others. Flora of North America (eFloras, 2008) and USDA-ARS (2008) list A. aethiopicus separately and the former states that the name Asparagus densiflorus has been misapplied to ‘this species’ (i.e. the cultivated material also known as A. sprengeri ) (Green 1986; Judd, 2001). Conversely, Sebsebe (2006) comments that Obermeyer (1993) kept the cultivated forms under A. densiflorus (Kunth) Jessop. In view of the taxonomical uncertainty over which it is being reported on in the literature, they will be considered together here under the name A. densiflorus unless it is necessary to specify.

 

Description

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A. densiflorus is a spiny perennial plant, persisting and spreading by fleshy rhizomes and roots bearing white tubers 2-3 cm long. Stems up to 2 m long are glabrous, green to brown, much-branched and ‘leafy’ but the clusters of flattened ‘leaves’ are in fact cladophylls about 2 cm long, 2-3 m wide. True leaves are represented by small scales at the base of the cladophylls. The stems also bear scattered straight spines, about 5 mm long, just below each branch. Flowers are in groups at the stem apices, white or pale pink, bell-shaped, with a corolla of 6 tepals and orange anthers. Fruit is a red berry 5-8 mm in diameter, containing one or a few seeds 3-4 mm in diameter (Parsons and Cuthbertson, 1992).

Plant Type

Top of page Herbaceous
Perennial
Seed propagated
Shrub
Vegetatively propagated
Woody

Distribution

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In its native area, A. densiflora is a plant of savanna thickets, widely distributed in eastern Africa from Ethiopia to South Africa (Burkhill, 1985), however, USDA-ARS (2008) gives the native range of both A. densifolius and A. aethiopicus as South Africa only.

It has been very widely introduced throughout the world as an ornamental, in private gardens and commercially for sale as a component of cut-flower arrangements, the foliage being used as a delicate ‘fern’. The extent to which it has become naturalised is not altogether clear, but it has certainly done so and become a problem in Australia and south-eastern USA. While it is uncertain whether or not it has become naturalised in many of the other countries to which it has been introduced, it is conversely quite certain that it is already present in cultivation in many more countries than those listed - not yet any problem, but posing a potential risk.

Distribution Table

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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/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Asia

ChinaPresentIntroducedMissouri Botanical Garden, 2008
Christmas Island (Indian Ocean)PresentIntroduced Invasive PIER, 2008
IsraelPresentIntroducedPhilosoph-Hadas et al., 2007
JapanPresentIntroducedPIER, 2008Bonin (Ogasawara)
-Ryukyu ArchipelagoPresentIntroducedPIER, 2008Bonin (Ogasawara)
Korea, Republic ofPresentIntroducedLee et al., 2003
TaiwanPresentIntroducedTu and Cheng, 1983 1985

Africa

EgyptPresentIntroducedAzzam and Tawfik, 2002
South AfricaPresentNativeUSDA-ARS, 2008
TanzaniaPresentNativeMissouri Botanical Garden, 2008As A. aethiopicus in forest reserve
-ZanzibarPresentNativeSebsebe, 2006+ Pemba
UgandaPresentNativeSebsebe, 2006

North America

BermudaPresentIntroducedKairo et al., 2003; GBIF, 2008
USAPresentPresent based on regional distribution.
-CaliforniaPresentIntroducedUSDA-NRCS, 2008
-FloridaPresentIntroduced Invasive USDA-NRCS, 2008
-HawaiiWidespreadIntroduced Invasive PIER, 2008Hawaii, Kauai Lanai, Maui
-MissouriPresentIntroducedMissouri Botanical Garden, 2008

Central America and Caribbean

BahamasPresentIntroducedKairo et al., 2003; GBIF, 2008
Costa RicaPresentIntroducedGBIF, 2008
Dominican RepublicPresentIntroducedMissouri Botanical Garden, 2008
El SalvadorPresentIntroducedMissouri Botanical Garden, 2008
HondurasPresentIntroducedMissouri Botanical Garden, 2008
NicaraguaPresentIntroducedMissouri Botanical Garden, 2008
Puerto RicoPresentIntroducedMissouri Botanical Garden, 2008

South America

ArgentinaPresentIntroducedMissouri Botanical Garden, 2008
EcuadorPresentPIER, 2008Galapagos
VenezuelaPresentIntroducedMaciel et al., 1999

Europe

GermanyPresentIntroducedGBIF, 2008
ItalyPresentIntroducedRusso et al., 2007
SpainPresentIntroducedGBIF, 2008
SwitzerlandPresentIntroducedGBIF, 2008

Oceania

AustraliaLocalisedIntroduced Invasive Parsons and Cuthbertson, 1992+ Lord Howe Island
-New South WalesLocalisedIntroduced Invasive DEWHA, 2008
-QueenslandLocalisedIntroduced Invasive DEWHA, 2008
-South AustraliaUnconfirmed recordIntroducedDEWHA, 2008
-VictoriaLocalisedIntroducedDEWHA, 2008
-Western AustraliaLocalisedIntroducedDEWHA, 2008
Cook IslandsPresentIntroducedPIER, 2008Raratonga
FijiPresentIntroducedPIER, 2008
French PolynesiaPresentIntroduced Invasive PIER, 2008Bora Bora., Raiatea, Taha'a, Tahiti
GuamPresentIntroducedPIER, 2008
Marshall IslandsPresentIntroducedPIER, 2008Kwjalein, Majuro
NauruPresentIntroducedPIER, 2008
New CaledoniaPresentIntroduced Invasive PIER, 2008IIe Grande Terre
New ZealandPresentIntroducedUSDA-ARS, 2008
NiuePresentPIER, 2008
Norfolk IslandLocalisedIntroduced Invasive DEWHA, 2008
Northern Mariana IslandsPresentIntroducedPIER, 2008Tinian Island
PalauPresentIntroducedPIER, 2008Koror, Ngerkebesang
SamoaPresentIntroducedPIER, 2008
TongaPresentIntroducedPIER, 2008Lifuka, Tongatapu, Vava'u

History of Introduction and Spread

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This plant has been known as an ornamental and widely introduced deliberately to many countries over the past two centuries. Dates of introduction are not generally known but Parsons and Cuthbertson (1992) indicate that it was first introduced to Australia at the end of the 1800s.

Introductions

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Introduced toIntroduced fromYearReasonIntroduced byEstablished in wild throughReferencesNotes
Natural reproductionContinuous restocking
Australia Late 1800s Yes Parsons and Cuthbertson (1992); Parsons and WT, Cuthbertson (1992); ParsonsWT, and Cuthbertson (1992)

Risk of Introduction

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Thanks to the very wide popularity of this plant as an ornamental, the risks of introduction and subsequent escape are very high indeed. Spread occurs partly from careless disposal of rhizomes in garden waste but also from dispersal of the seeds by birds eating the attractive red berries (Parsons and Cuthbertson, 1992).

Habitat

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The natural habitat of A. densiflorus in eastern Africa from Ethiopia to South Africa is dry to moist forest, woodland, forest edges, savanna, shady roadsides, and along riversides, also infertile, shallow, sandy soils of coastal sand dunes, beaches, cliffs and scrub. It is tolerant of salinity and may grow close to mangrove swamp (Skimina, 1980). In Australia it is a plant of warm temperate regions with temperatures of 10-20°C (DEWHA, 2008).

Habitat List

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CategorySub-CategoryHabitatPresenceStatus
Terrestrial
 
Terrestrial – ManagedProtected agriculture (e.g. glasshouse production) Secondary/tolerated habitat Productive/non-natural
Managed forests, plantations and orchards Secondary/tolerated habitat Harmful (pest or invasive)
Disturbed areas Principal habitat Harmful (pest or invasive)
Disturbed areas Principal habitat Natural
Rail / roadsides Principal habitat Harmful (pest or invasive)
Rail / roadsides Principal habitat Natural
Urban / peri-urban areas Secondary/tolerated habitat Harmful (pest or invasive)
Urban / peri-urban areas Secondary/tolerated habitat Natural
Urban / peri-urban areas Secondary/tolerated habitat Productive/non-natural
Terrestrial ‑ Natural / Semi-naturalNatural forests Principal habitat Harmful (pest or invasive)
Natural forests Principal habitat Natural
Natural grasslands Secondary/tolerated habitat Harmful (pest or invasive)
Natural grasslands Secondary/tolerated habitat Natural
Riverbanks Principal habitat Harmful (pest or invasive)
Riverbanks Principal habitat Natural
Wetlands Secondary/tolerated habitat Harmful (pest or invasive)
Wetlands Secondary/tolerated habitat Natural
Scrub / shrublands Principal habitat Harmful (pest or invasive)
Scrub / shrublands Principal habitat Natural
Littoral
Coastal areas Principal habitat Harmful (pest or invasive)
Coastal areas Principal habitat Natural
Coastal dunes Principal habitat Harmful (pest or invasive)
Coastal dunes Principal habitat Natural
Mangroves Secondary/tolerated habitat Harmful (pest or invasive)
Mangroves Secondary/tolerated habitat Natural

Hosts/Species Affected

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A. densiflorus is rarely a weed in any agricultural crop.

Biology and Ecology

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Genetics 

Chromosome number is variously recorded as 2n=40 or 2n=60. Dasgupta et al. (2007) refer to 2n=60 as ‘diploid’ but Marcellán and Camadro (1999) found this number in var. sprengeri and refer to it as hexaploid, 2n = 20 being the diploid number for A. officinalis. Sheidai and Inamdar (1992) found var. myers and ‘A. sprengeri’ to be tetraploid (2n = 40), while Kar and Sumitra Sen (1986) recorded ‘A. sprengeri’ as hexaploid, but A. densiflorus var. pyrimidalis as diploid. Missouri Botanical Garden (2008) states that A. densiflorus is only tetraploid, but tetraploid or hexaploid for ‘A. sprengeri’.

Reproduction

Unlike those of the crop asparagus, which is dioecious, the flowers of A. densiflorus are hermaphrodite. They are fragrant but can apparently be self-pollinated as well as cross-pollinated (Camadro, 1994; PIER, 2008). One to three seeds are formed in a red berry which is dispersed by birds.

Physiology and Phenology

Seeds may germinate at any time of the year where introduced in Australia but there is a major flush in the spring and a smaller one in the autumn. Germination can occur from below 10°C upwards, in light or darkness (Massante, 1963). Establishment is relatively slow until the roots are well developed, and tubers form on the rhizomes throughout the early summer. Flowering occurs in late winter and spring through to early summer and foliage may die back during mid-summer, with a fresh flush of rhizome and tuber development each season and fruits may be present throughout the year (Parsons and Cuthbertson, 1992).

Climate

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ClimateStatusDescriptionRemark
As - Tropical savanna climate with dry summer Tolerated < 60mm precipitation driest month (in summer) and < (100 - [total annual precipitation{mm}/25])
Aw - Tropical wet and dry savanna climate Tolerated < 60mm precipitation driest month (in winter) and < (100 - [total annual precipitation{mm}/25])
Cf - Warm temperate climate, wet all year Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, wet all year
Cs - Warm temperate climate with dry summer Preferred Warm average temp. > 10°C, Cold average temp. > 0°C, dry summers
Cw - Warm temperate climate with dry winter Preferred Warm temperate climate with dry winter (Warm average temp. > 10°C, Cold average temp. > 0°C, dry winters)

Latitude/Altitude Ranges

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Latitude North (°N)Latitude South (°S)Altitude Lower (m)Altitude Upper (m)
40 40 0 0

Air Temperature

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Parameter Lower limit Upper limit
Mean annual temperature (ºC) 15 25
Mean maximum temperature of hottest month (ºC) 0 33
Mean minimum temperature of coldest month (ºC) -5 0

Rainfall

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ParameterLower limitUpper limitDescription
Dry season duration06number of consecutive months with <40 mm rainfall
Mean annual rainfall5002000mm; lower/upper limits

Rainfall Regime

Top of page Bimodal
Summer
Uniform
Winter

Soil Tolerances

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Soil drainage

  • free

Soil reaction

  • acid
  • alkaline
  • neutral

Soil texture

  • light
  • medium

Special soil tolerances

  • infertile
  • saline
  • shallow

Notes on Natural Enemies

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Preliminary surveys of natural enemies of Asparagus species in South Africa have suggested a chalcid wasp, a moth larva and a rust to be of potential interest. There is also galling by the chalcids Asparagobius braunsii and a Eurytoma species (Parsons and Cuthbertson, 1992).

Greenhouse-grown A. densiflorus in Poland is attacked by the spiral nematode Scutellonema brachyurum (Wojtowicz and Szczygiel, 1990). In France it is a host to Corynebacterium fascians (Faivre-Amiot, 1967), and in Germany, to Pseudomonas tumefaciens (Stapp, 1940) and Phytomonas fascians[Rhodococcus fascians] (Pape, 1938). In USA it is believed to have been infected by Agrobacterium tumefaciens (Brown and Weiss, 1937).

 

Means of Movement and Dispersal

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Natural Dispersal (Non-Biotic)

Local spread occurs by rhizome growth.

Vector Transmission (Biotic)

Natural dispersal is by birds eating the fleshy berries.

Accidental Introduction

Accidental spread occurs as a result of careless disposal of garden waste containing rhizome or tuber material.

Intentional Introduction

Deliberate introduction occurs very commonly, for horticultural purposes.

Pathway Causes

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CauseNotesLong DistanceLocalReferences
Botanical gardens and zoos Yes Yes
Cut flower trade Yes Yes
Digestion and excretionFruit eaten by birds Yes
Escape from confinement or garden escape Yes
Garden waste disposal Yes
HorticultureAs an ornamental Yes Yes
Internet sales Yes Yes
Landscape improvement Yes Yes
Nursery trade Yes Yes
Ornamental purposes Yes Yes

Pathway Vectors

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VectorNotesLong DistanceLocalReferences
Aircraft Yes
Debris and waste associated with human activities Yes
Land vehicles Yes
Mail Yes Yes

Impact Summary

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CategoryImpact
Cultural/amenity Positive and negative
Economic/livelihood Positive
Environment (generally) Negative

Economic Impact

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A. densiflorus does not generally affect agricultural crops, but there can be an economic cost for control where the weed threatens to cause environmental damage.

Environmental Impact

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The weed forms dense blankets of growth above ground and a mass of roots and rhizome below, suppressing other ground flora and depleting soil moisture and nutrients. It is among the most abundant invasive ornamental weeds of sandy beachfronts in Queensland, Australia (Batianoff and Franks, 1997). It has also become established and threatens natural vegetation on Lord Howe Island, Norfolk Island and a number of other islands in the Pacific Ocean (Parsons and Cuthbertson, 1992; PIER, 2008).

In Florida, USA it has escaped in a number of localities into e.g. scrub vegetation displacing native ground cover and understory shrubs, also overtopping native wild coffee (Psychotria nervosa) (IFAS, 2008), and it is of sufficient concern for it to be recommended for voluntary withdrawal from sale in the state (Wirth et al., 2004). In Hawaii, USA it is spreading along roadsides and invading secondary forest (PIER, 2008).

Risk assessment score for Australia is 3 (‘requiring evaluation’) and for Pacific Islands is 15 (‘high risk’) (PIER, 2008).

Threatened Species

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Threatened SpeciesConservation StatusWhere ThreatenedMechanismReferencesNotes
Psychotria nervosaNo DetailsFloridaCompetition - monopolizing resources; Competition - shading; Competition - smotheringeFloras, 2008

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Highly adaptable to different environments
  • Tolerates, or benefits from, cultivation, browsing pressure, mutilation, fire etc
  • Pioneering in disturbed areas
  • Tolerant of shade
  • Highly mobile locally
  • 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
Impact outcomes
  • Damaged ecosystem services
  • Ecosystem change/ habitat alteration
  • Modification of nutrient regime
  • Modification of successional patterns
  • Monoculture formation
  • Negatively impacts forestry
  • Reduced native biodiversity
  • Threat to/ loss of endangered species
  • Threat to/ loss of native species
Impact mechanisms
  • Competition - monopolizing resources
  • Competition - shading
  • Competition - smothering
  • Rapid growth
Likelihood of entry/control
  • Highly likely to be transported internationally deliberately
  • Difficult to identify/detect in the field
  • Difficult/costly to control

Uses

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The main use for A. densiflorus is as an ornamental plant, whether grown as a whole plant in the garden, or for the cut foliage incorporated into floral decorations. The latter is a major commercial commodity in both local and international trade in Europe, North America and Asia. A number of different varieties are involved.

Among medicinal uses, mashed leaves are applied to cuts and tubers are given to children for stomach ache.

In Canada, the cladophylls of A. densiflorus have been the source of mesophyll cells for many detailed plant physiological studies (Guinel and Bown, 1994).

It has been regarded as a potentially useful source of resistance to pathogens such as Phoma asparagi (Tu and Cheng, 1985) and to F. oxysporum f. sp. asparagi and F. moniliforme [Gibberella fujikuroi] (Stephens et al., 1989).

Uses List

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Environmental

  • Amenity
  • Landscape improvement

General

  • Botanical garden/zoo
  • Laboratory use

Genetic importance

  • Gene source

Medicinal, pharmaceutical

  • Traditional/folklore

Ornamental

  • Cut flower
  • Potted plant
  • Propagation material

Similarities to Other Species/Conditions

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A. densiflorus is superficially similar to many other Asparagus spp. including the cultivated vegetable A. officinalis. The latter has narrower, needle-like cladodes and white to pale yellow flowers on long pedicels. A. plumosus is also a cultivated ornamental but is a climbing plant with very long branches up to 5 m long and with few, down-curved spines, or none, and black berries. A. asparagoides has fewer, larger, alternate cladodes, much larger, 1-7 cm long, 1-3 cm wide. A. scandens has narrower leaves up to 1.5 mm wide, solitary flowers and a more climbing habit. A. racemosus has many longer spines up to 2 cm long.

Prevention and Control

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Control

Mechanical control

Where A. densiflorus has become established outside the intended area, digging out the rhizomes and tubers may be feasible but is unlikely to be successful without some repetition.

Chemical control

Parsons and Cuthbertson (1992) recommend dicamba applied to seedlings or to re-growth following digging or slashing. In New Zealand, glyphosate is recommended (EBPRC, 2008).

Biological control

Some potential biological control agents have been identified in South Africa but none has so far been developed for biological control.

References

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Azzam KM; Tawfik MFS, 2002. Snail preference of the malacophagous sarcophagid Parasarcophaga pharaonis (Rohdendorf) (Diptera: Sarcophagidae). Egyptian Journal of Biological Pest Control, 12(2):125-128.

Batianoff GN; Franks AJ, 1997. Invasion of sandy beachfronts by ornamental plant species in Queensland. Plant Protection Quarterly, 12(4):180-186; 26 ref.

BROWN NA; WEISS F, 1937. Crown gall of the fasciated type on Asparagus sprengeri. Plant Disease Reporter, 21(2):31-32 pp.

Burkill HM, 1985. The useful plants of West Tropical Africa. Vol. 1. Families A- D. Kew, UK: Royal Botanic Gardens, xvi + 960pp.

Camadro EL, 1994. Genetic basis of low seed production in garden and ornamental asparagus. Asparagus Research Newsletter, 11(1/2):16-18.

Dasgupta CN; Mukhopadhyay MJ; Sandip Mukhopadhyay, 2007. Somatic embryogenesis in Asparagus densiflorus (Kunth) Jessop cv Sprengeri. Journal of Plant Biochemistry and Biotechnology, 16(2):145-149. http://www.iospress.nl

DEWHA, 2008. Weeds in Australia. Canberra, Australia: Department of the Environment, Water Heritage and the Arts. http://www.weeds.gov.au/

EBPRC, 2008. Weed Index. Whakatane, New Zealand: Environment Bay of Plenty Regional Council. http://www.envbop.govt.nz/Weeds/Weed-Index.asp

eFloras, 2008. . efloras.org. http://www.efloras.org/index.aspx

Faivre-Amiot A, 1967. Observations on C. fascians in market and flower crop cultivation in France. (Quelques observations sur la presence de Corynebacterium fascians (Tilford) Dowson dans les cultures maraíchéres et florales en France.) Phytiatrie-Phytopharmacie, 16(3):165-176.

GBIF, 2008. Global Biodiversity Information Facility. GBIF. http://www.gbif.org/

Green PS, 1986. The correct name for Asparagus sprengeri. Plantsman, 7(4):249-250.

Guinel FC; Bown AW, 1994. Mechanically isolated photosynthetic cells from asparagus cladophylls originate from two distinct tissue locations. Canadian Journal of Botany, 72(7):1051-1056.

IFAS, 2008. Center for Aquatic and Invasive Plants. Gainesville, Florida, USA: University of Florida. http://plants.ifas.ufl.edu/

Judd WS, 2001. The Asparagaceae in the southeastern United States, 6:223-244.

Kairo M; Ali B; Cheesman O; Haysom K; Murphy S, 2003. Invasive species threats in the Caribbean region. Report to the Nature Conservancy. Curepe, Trinidad and Tobago: CAB International, 132 pp. http://www.issg.org/database/species/reference_files/Kairo%20et%20al,%202003.pdf

Kar DK; Sumitra Sen, 1986. Content of sapogenins in diploid, tetraploid and hexaploid Asparagus. International Journal of Crude Drug Research, 24(3):131-133.

Lee HJ; Byun MS; Kim KW, 2003. Retardation of yellowing and abscission by benzyladenine spray treatment in cut leaves of Asparagus [ed. by Journal of the Korean Society for Horticultural Science]. Korea: Journal of the Korean Society for Horticultural Science, 238-244.

Lee HyunJoo; Byun MiSoon; Kim KiuWeon, 2003. Retardation of yellowing and abscission by benzyladenine spray treatment in cut leaves of Asparagus. Journal of the Korean Society for Horticultural Science, 44(2):238-244.

Maciel N; Mogollón N; Mendoza A, 1999. Germination and emergence of four cut foliage Asparagus species. (Germinación y emergencia de cuatro espárragos (Asparagus spp.) usados como follaje de corte.) Revista de la Facultad de Agronomía, Universidad del Zulia, 16(2):160-166.

Marcellán ON; Camadro EL, 1999. Formation and development of embryo and endosperm in intra- and inter-specific crosses of Asparagus officinalis and A. densiflorus cv. Sprengeri. Scientia Horticulturae, 81(1):1-11.

Massante H, 1963. Investigations on the effect of temperature on the storage and germination of seeds of ornamental plants. (Untersuchungen über den Einfluss der Temperatur auf die Lagerung und Keimung von Zierpflanzensamen.) Gartenbauwissenschaft, 28:173-97.

Missouri Botanical Garden, 2013. VAScular Tropicos database. Missouri, USA: Missouri Botanical Garden. http://mobot.mobot.org/W3T/Search/vast.html

Pape H, 1938. An as yet little heeded disease of ornamentals. (Eine noch wenig beaohtete Krankheit der Zierpflanzen.) Blumen- u. PflBau ver. Gartenwelt, 42(32):384-386 pp.

Parsons WT; Cuthbertson EG, 1992. Noxious Weeds of Australia. Melbourne, Australia: Inkata Press, 692 pp.

Philosoph-Hadas S; Droby S; Rosenberger I; Perzelan Y; Salim S; Shtein I; Meir S, 2007. Sea transport of ornamental branches: problems and solutions. Acta Horticulturae, No.755:267-276. http://www.actahort.org

PIER, 2008. Pacific Islands Ecosystems at Risk. Hawaii, USA. HEAR. http://www.hear.org/pier/index.html

Russo G; D'Errico FP; Abagnale A, 2007. Meloidogyne hapla: a problem for ornamental foliage in southern Italy. (Meloidogyne hapla: un problema nel sud Italia per il verde ornamentale.) Colture Protette, 36(2):83-85. http://www.enzazadenitalia.it

Sebsebe D, 2006. Flora of Tropical East Africa [ed. by Royal Botanic Gradens]. UK: Royal Botanic Gradens.

Sheidai M; Inamdar AC, 1992. Polyploidy in the genus Asparagus L. Nucleus (Calcutta), 35(2/3):93-97.

Skimina CA, 1980 1981. Salt tolerance of ornamentals. In: Combined Proceedings, International Plant Propagators' Society, 113-118.

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06/05/08 Original text by:

Chris Parker, Consultant, UK

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