Romula rosea_Neal Kramer
Photo by Neal Kramer

Romulea rosea Risk Assessment

Common names: rosy sandcrocus

Romulea rosea -- California

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Evaluation Summary
Summary: 
General Evaluation Information
Date of Evaluation: 
August 20, 2016
Evaluation Time (hrs): 
2 Hours
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: 
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: 
High
Answer / Justification: 
Naturalized with many records in in southern Australia, New Zealand (GBIF), California (Calflora).
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: 
High
Answer / Justification: 
This species is naturalized in far southwestern Western Australia (Florabase), south Australia, Victoria and New South Wales in areas that match California's climate (GBIF).
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: 
Medium
Answer / Justification: 
Common onion grass (Romulea rosea) is a significant environmental weed in Victoria and Western Australia, and an environmental weed in South Australia, the ACT and New South Wales.
Reference(s): 
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: 
Low
Answer / Justification: 
DiTomaso and Healy lists this as an "uncommon ornamental escape" in California in disturbed areas. A TNC weed alert from 2001 as well as an Victoria Agriculture Note state that this is invasive mainly in pastures and disturbed areas.
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: 
Medium
Answer / Justification: 
No Romuleas are on any state or federal noxious lists and none show up in Invasive.org or the US Invasive Plant Atlas, or in DiTomaso and Healy. However, Romulea minutiflora is noted as an environmental weed in Australia in a similar climate.
Reference(s): 
6. Is the species (or cultivar or variety) found predominately in a climate matching the region of concern?
Yes or No: 
Yes
Points: 
2
Confidence Level: 
High
Answer / Justification: 
In GBIF, and USDA GRIN, the native range of the species is South Africa, specifically the southern tip of the Cape Region, which matches California's climate. This species is naturalized in far southwestern Western Australia (Florabase), south Australia, Victoria and New South Wales in areas that match California's climate (GBIF). The only areas with more than 1 location documented in GBIF that do not match California's climate, is the North Island of New Zealand.
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: 
No
Points: 
0
Confidence Level: 
Low
Answer / Justification: 
It is unclear that this plant is good at outcompeting/overtoping existing vegetation. It seems to invade low-competition areas, spread given the opportunity and persist. Agriculture Victoria: "In crops and pastures, onion grass often grows ahead of desirable species, utilising valuable moisture and nutrients and restricting production..."The two main causes of onion grass infestation are autumn bare ground and lack of competition from desirable pasture species. Prevention involves managing pastures to maintain above 70 per cent ground cover and maximising growth during autumn and winter."
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 species is noted as occuring in disturbed post-fire environments but no evidence that it promotes fire. It is a short-statured plant.
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: 
Yes
Points: 
1
Confidence Level: 
Medium
Answer / Justification: 
According to Agriculture Victoria, this plant reduces pastures by replacing more nutritional plants and may cause death if too much of it is ingested by grazing animals.
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: 
High
Answer / Justification: 
This plant is of short stature, and does not therefore impede movement of large animals or humans.
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: 
This species produces corms which produce the perennial growth from underground.
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: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
This species produces corms that build up in the soil locally.
Reference(s): 
13. Does the species (or cultivar or variety) commonly produce viable seed?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
High
Answer / Justification: 
This species may be propagated by seed.
Reference(s): 
14. Does this plant produce copious viable seeds each year (> 1000)?
Yes or No: 
No
Points: 
0
Confidence Level: 
Medium
Answer / Justification: 
Agriculture Victoria notes "abundant seed," and that large numbers of seeds may be dipsersed by sheep, however this seems to be due to high density of plants, not high seed set. Agriculture Victoria also notes 310 seed pods per 3340 plants, giving <0.1 pods per plant. As well, a study by Nie et al. (2012) also noted similar low pod set per plant, 768 pods per 4143 plants. Much of the spread seems to be not by seed, but by corm, and the high seed set is per area, not 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: 
Medium
Answer / Justification: 
Eddy and Smith (1975) studied onion grass seed germination in the context of animal dispersal-- germination was measured in seeds from sheep scat. By 6 weeks, germination was 38% in fecal samples, and 96% in the control.
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: 
Medium
Answer / Justification: 
Time to flower is 2 years.
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: 
Answer / Justification: 
This species is noted as flowering for 4 months in the state of Victoria, Australia and 3 months in Western Australia.
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: 
Medium
Answer / Justification: 
Several references to the ability for animals to transport seeds from area to area.
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: 
Although seeds are noted to be able to be moved (as most biomass is), there are no specific adaptations for dispersing via wind or water. Seed
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 specific adaptation for attachment and dispersal via these mechanisms. Queensland Biosecurity lists the possibility of dispersal when mowing or slashing, but this would seem to be very localized. The GISP Alert site lists the spread in California via contaminated seed, but could find noevidence that this is a frequent means of spread.
Reference(s): 
Evaluation Notes
Total PRE Score

  • < 13 : accept (low risk of invasiveness)
  • 13 - 15 : evaluate further
  • > 15 : reject (high risk of invasiveness)

PRE Score: 
19
Number of questions answered: 
20
Screener Confidence (%): 
62.0
PRE Content Access and Privacy
Evaluation visibility: 
Public - accessible to all site users

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