Photo: Ron Vanderhoff

Asparagus aethiopicus Risk Assessment

Synonyms: Asparagus sprengeri, Asparagus densiflorus

Common names: asparagus fern, Sprenger's Asparagus, foxtail fern

Asparagus aethiopicus -- California

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Evaluation Summary
This perennial is native to South Africa, and is used in the horticulture industry as an ornamental plant (aka Asparagus fern, which is not a true fern). It has been distributed throughout many parts of the world through the horticulture industry as its distinctive branching and leafing pattern can be attractive to gardeners. This species has been listed as invasive in several areas of the globe, mostly in wetter areas than California, but also in Coastal areas that are similar to California. This species is also spreading in some natural areas in Southern California. Synonyms for this species include Asparagus densiflorus, and Protaspargus densiflorus, which is a separate species but was mis-ascribed to this species and is sometimes called this incorrect name by organizations especially in Australia. A. densiflorus is currently not found in Australia, but publications mistakenly call A. aethiopicus, A. densiflorus or P. densiflorus. See Asparagus Weeds Management Manual (page 11) in citations for more details.
General Evaluation Information
Date of Evaluation: 
September 13, 2021
Evaluation Time (hrs): 
Not Recorded
Evaluation Status: 
Completed
Plant Information
Plant Material: 
If the plant is a cultivar, and if the cultivar's behavior differs from its parent's (behavior), explain how: 
Regional Information
Region Name: 
Climate Matching Map
These maps were built using a toolkit created in collaboration between GreenInfo Network, PlantRight, Cal-IPC, and Agricultural Sustainability Institute at UC Davis.
Climate Matching Maps PDF: 
AttachmentSize
PDF icon CA_Matching_Results Asparagus A.pdf503.38 KB
Invasive History and Climate Matching
1. Has the species (or cultivar or variety, if applicable; applies to subsequent "species" questions) become naturalized where it is not native?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
It is invasive and naturalized in Florida, Hawaii, Australia and also found in South America.
Reference(s): 
2. Is the species (or cultivar or variety) noted as being naturalized in the US or world in a similar climate?
Yes or No: 
Yes
Points: 
2
Confidence Level: 
Very High
Answer / Justification: 
This species is currently naturalized in California and is also naturalized in eastern Australia in New South Wales, and Spain, where the climate matches California
Reference(s): 
3. Is the species (or cultivar or variety) noted as being invasive in the U.S. or world?
Yes or No: 
Yes
Points: 
2
Confidence Level: 
Very High
Answer / Justification: 
Yes it is noted as being invasive (spreading and causing harm) in Australia, Florida and Hawaii.
4. Is the species (or cultivar or variety) noted as being invasive in the US or world in a similar climate?
Yes or No: 
Yes
Points: 
3
Confidence Level: 
High
Answer / Justification: 
Noted as being invasive and in Australia, NSW, where the climate matches California. It is also found in Coastal Southern California in natural areas. In coastal Southern California most current locations are found near the wildland urban interface.
Reference(s): 
5. Are other species of the same genus (or closely related genera) invasive in a similar climate?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Asparagus asparagoides is invasive in California. Other Asparagus species are also invasive and/or naturalized in Australia.
6. Is the species (or cultivar or variety) found predominately in a climate matching the region of concern?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
Most of the locations for Asparagus aethiopicus are in more tropical areas, such as the southeastern US, Hawaii, Central America, and north eastern Australia (Queensland).
Reference(s): 
Impact on Native Plants and Animals
7. Does this plant displace native plants and dominate (overtop or smother) the plant community in areas where it has established?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
From the NSW Weed Wise website: "Ground asparagus forms dense blankets of growth above ground and a profusion of roots and tubers below ground which suppresses other ground flora and reduces available soil moisture and nutrients." The Weeds of Australia website says "Ground asparagus (Asparagus aethiopicus 'Sprengeri') forms a thick mat of tuberous roots and grows particularly well in shaded areas and in sandy soils." "The dense growth of this species may form impenetrable thickets that smother native understorey plants and inhibit their regeneration, thereby transforming the ground layer of native plant communities."
Reference(s): 
8. Is the plant noted as promoting fire and/or changing fire regimes?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
This plant does not contain a lot of leaves and does not create a lot of fuel. The branches are thin, the leaves are small and long. It is also a perennial of mostly shady locations, often near the coast, and does not dry out completely to create highly flammable fuels with low fuel moisture.
Reference(s): 
9. Is the plant a health risk to humans or animals/fish? Has the species been noted as impacting grazing systems?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
This species appears only toxic to dogs and cats. If it is toxic to livestock, it does not appear to invade grasslands and the likelihood is that few livestock would eat it. It is not likely that livestock eat this species, although one source (Lusigi et. al 1984) show that this species can be a minor (20% or less) component of goat forage in the wet season in Kenya.
Reference(s): 
10. Does the plant produce impenetrable thickets, blocking or slowing movement of animals, livestock, or humans?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
This species spreads and can form mats along the ground and can suppress other plants from growing or establishing. It is difficult to determine if these mats suppress the spread of animals. The plant is low growing or grows inside other plants using them as support so it is unlikely they would slow the movement of livestock or humans. It is unknown if it could inhibit movements of smaller animals. From the NSW Weed Wise website: "Ground asparagus forms dense blankets of growth above ground and a profusion of roots and tubers below ground which suppresses other ground flora and reduces available soil moisture and nutrients." From Asparagus Weeds Management Manual "Asparagus aethiopicus creates vigorous thickets of foliage that forms dense spiny mats. It can quickly invade disturbed sites in open sun or partial shade. Plants can form monocultures that smother and displace native herbs and shrubs, and can form impenetrable root mats below the ground that may impede the growth of native seedlings. The above ground biomass can dominate the native ground and shrub layer."
Reference(s): 
Reproductive Strategies
11. Does this species (or cultivar or variety) reproduce and spread vegetatively?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Main mode of reproduction is by seeds and to a lesser extent by vegetative spread. It can spread if rhizomes are transported, such as by gardeners or infected poorly processed compost or following disturbance that separates rhizomes from the plant. The plant can also be propagated by dividing the central crowns (rhizomes), but the underground tubers are storage organs are do not promote vegetative spread. Most spread is not by vegetative plant parts, but by the spread of seeds.
Reference(s): 
12. If naturally detached fragments from this plant are capable of producing new plants, is this a common method of reproduction for the plant?
Yes or No: 
No
Points: 
0
Confidence Level: 
High
Answer / Justification: 
It does not appear the spread of plant fragments is a common method of dispersal. "Spread is primarily by seeds" -Asparagus Weed Management Manual.
Reference(s): 
13. Does the species (or cultivar or variety) commonly produce viable seed?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
The main method of reproduction is seed.
Reference(s): 
14. Does this plant produce copious viable seeds each year (> 1000)?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
"Up to 600 mature fruit were observed on a single plant at one time, and while most fruit was observed on bushes in May and June, ripe fruit was observed in every month of the year." Plants can also produce 3 seeds per fruit and if there are 2-3 seeds per fruit on some plants there will be over 1,000 seeds per plant.
Reference(s): 
15. Is there significant germination (>25%) of seeds the next growing season, with no requirement of an infrequent environmental condition for seeds to germinate (i.e. fire) or long dormancy period?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Germination was greater than 30% after 30 days of collecting fruits in both February and April.
Reference(s): 
16. Does this plant produce viable seed within the first three years (for an herbaceous species) to five years (for a woody species) after germination?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
Plants mature within 1.5 - 2 years (see source page 12)
Reference(s): 
17. Does this plant continuously produce seed for >3 months each year or does seed production occur more than once a year?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
"Up to 600 mature fruit were observed on a single plant at one time, and while most fruit was observed on bushes in May and June, ripe fruit was observed in every month of the year."
Reference(s): 
Dispersal
18. Are the plant’s propagules frequently dispersed long distance (>100 m) by mammals or birds or via domestic animals?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
Several sources suggest birds are one dispersal agent, and move seeds "far from the main plant." Presumably birds ingest the fruits and disperse the seeds long distances.
Reference(s): 
19. Are the plant’s propagules frequently dispersed long distance (>100 m) by wind or water?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
The main way this species reproduces is through dispersal of seeds in the fruits. Birds and other wildlife are believed to be primary dispersers. The fruits are round and heavy and cannot be dispersed by wind; they could roll down hill in some unique situations. Available sources do not mention if the fruits float and emphasize dispersal by wildlife.
Reference(s): 
20. Are the plant’s propagules frequently dispersed via contaminated seed (agriculture or wildflower packets), equipment, vehicles, boats or clothing/shoes?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
No, the main dispersal for this species is seeds by birds and by plant parts (crown divisions, rhizomes) intentionally by gardeners, not by contaminated seed, equipment vehicles or clothing. Fruits and plant propagules, such as rhizomes would be spread intentionally by gardeners, or in infected compost or soil, but would not be frequent.
Reference(s): 
Evaluation Notes
Notes: 
Total PRE Score

  • < 13 : Low Potential Risk
  • 13 - 15 : Moderate Potential Risk
  • > 15 : High Potential Risk

PRE Score: 
17
Number of questions answered: 
20
Screener Confidence (%): 
82.0
PRE Content Access and Privacy
Evaluation visibility: 
Private - accessible only to organization members

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