Photo: Jennifer Mo

Lythrum junceum Risk Assessment

Synonyms: Lythrum graefferi, Lythrum monanthum

Common names: creeping loosestrife, rose loosestrife

Lythrum junceum -- California

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Created by: Lynn Sweet
Created on: Monday, Oct 11th, 2021
Evaluation Summary
This species is native to Europe and the Mediterranean region. It is noted in just a few areas worldwide outside of that area; but where it has been found, it is often listed as locally abundant. It may have been misidentified in the past in California, however, which probably contributes to a lack of information about the species. The 2019 paper describing the former misidentification states that it is surprising that it is not more widespread given its long history and local abundance-- this could definitely be due to misidentification in the state. Therefore, there may be new information about the region of concern once it is more widely identified. I have low confidence in the questions about invasiveness.
General Evaluation Information
Date of Evaluation: 
October 11, 2021
Evaluation Time (hrs): 
Not Recorded
Evaluation Status: 
Completed
Plant Information
Plant: 
Lythrum junceum
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: 
California
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.
Link to Climate Matching Map: 
Climate Matching Maps PDF: 
AttachmentSize
PDF icon PRE_CA_Matching_Results.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: 
This species is native to Europe, but has been documented in both California (Santa Clara and Alameda Counties) and South Australia, and New Zealand.
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: 
The species has naturalized in Alameda and Santa Clara Counties in coastal California, the region of interest. One of the observations from California notes, "Flowering, fruiting; low-growing perennial along creek and in wetlands." Importantly this observation by K. Hickman includes botanical detail to differentiate the ID from L. californicum (a native species historically confused). https://www.calflora.org/entry/occdetail.html?seq_num=po164252
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: 
From the published literature, it was seen in California, the region of interest, "dominating a spring area protected from grazing near the main trailhead" and "populations were located at almost every wetland site in Mission Peak Regional Preserve, and the species is often a dominant species at these sites". (Ertter & Gowen) I gave a medium confidence because this dominance wasn't described as invasive, but this is listed under a paper sub-heading "Invasive Status", so it's inferred.
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: 
Medium
Answer / Justification: 
From the published literature, it was seen in California, the region of interest, "dominating a spring area protected from grazing near the main trailhead" and "populations were located at almost every wetland site in Mission Peak Regional Preserve, and the species is often a dominant species at these sites". (Ertter & Gowen) I gave a medium confidence because this dominance wasn't described as invasive, but this is listed under a paper sub-heading "Invasive Status", so it's inferred.
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: 
Yes. Lythrum salicaria (purple loosestrife) is present within California, the region of interest. Purple loosestrife is a well-known and documented invasive species of wetlands in many regions of the globe including California. (Houghton-Thomson et al.) A second species in the genus, Lythrum hyssopifolia (Hyssop loosestrife) is is noted by Cal-IPC to have limited potential to invade new habitats in California, and somewhat poor competitive ability after initially invading sites as an early successional species, but it is widespread. (Bauder 1996). Literature on Lythrum salicaria supports a high confidence here.
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: 
Medium
Answer / Justification: 
The climate matches the region of concern where the species is present within its native range within Europe within southern Europe, and the area surrounding the Mediterranean, in the Middle East and North Africa; not matching the climate in areas (less than 50%) within Northern Europe and Great Britain. The non-native presences in California are within the region of concern. The presences in South Australia and New South Wales generally match the climate of the region of concern, and about half of the occurrences elsewhere in central and Western Australia match the region of concern.
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: 
Very Low
Answer / Justification: 
While the plant was described as dominant in several areas, it was never mentioned that it was displacing native plants specifically. There was a general lack of information about this species, and in many cases this may be because plants were misidentified as L. californica -- the new (2019) Ertter & Gowen paper described this misidentification and gives some information on its status in California. The only other information I have with specific information is the the Calflora observations with location notes. In New Zealand listed as locally common.
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 a low growing herbaceous perennial that inhabits riparian areas and no evidence of the species contributing to fire.
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: 
High
Answer / Justification: 
Cattle grazing stated to reduce the biomass of the species (Erttner & Gowen). No other mention of the species being a health risk.
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: 
Low growing herbaceous perennial species. While it is noted as creeping and stoloniferous, it is unlikely this would contribute to thickets or inhibit movement.
Reference(s): 
Reproductive Strategies
11. Does this species (or cultivar or variety) reproduce and spread vegetatively?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
From a peer-reviewed study of the species, authors indicated that the plants "...thrive vegetatively, spreading by strongly rooted stolons" (Ertter and Bowen)
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: 
Medium
Answer / Justification: 
The plants live in wetland habitats (though rooted near-shore from descriptions), and disturbance in these areas could easily lead to spread.
Reference(s): 
13. Does the species (or cultivar or variety) commonly produce viable seed?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Medium
Answer / Justification: 
The species produces viable seed, but apparently is self-incompatible and requires other plants present. (Ertter & Gowen)
Reference(s): 
14. Does this plant produce copious viable seeds each year (> 1000)?
Yes or No: 
No
Points: 
0
Confidence Level: 
Very Low
Answer / Justification: 
This plant is a short herbaceous perennial species (20–70 cm). But I was unable to find an estimate of seed production per plant. The flowers are listed as solitary in the axils (South Australia website), the Go Botany page has some information about morphology (2 capsules per flower), and the Dulberger paper lists up to 14 seeds per capsule. It's hard to imagine that this species could therefore produce copious seeds. However, its congener, purple loosestrife is known to be a highly prolific seeder with 100k+ seeds per plant per year (FEIS page for that species).
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: 
Germination of seeds at Kew assessed using a typical cold stratification period, and was listed as 80-90%. This would not be an infrequent condition.
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: 
Points: 
Confidence Level: 
Very Low
Answer / Justification: 
This plant is a short herbaceous perennial species, and would likely flower within the first year or two, but I was unable to find much information on this. The Go Botany page has some information about morphology, but nothing specific enough to answer this question.
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: 
High
Answer / Justification: 
Flora of South Australia lists flowering time as Nov-May in the southern hemisphere; Calflora lists flowering as May-Oct in California in the northern hemisphere.
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: 
No
Points: 
0
Confidence Level: 
Very Low
Answer / Justification: 
The New Zealand Plant Conservation site lists that seed can be transported by animals but this is not specifically supported or corroborated by life history. Low growing herbaceous perennial that inhabits riparian areas. No specific adaptations for dispersal via animals noted in the literature (attractive fruit or adhering structure).
Reference(s): 
19. Are the plant’s propagules frequently dispersed long distance (>100 m) by wind or water?
Yes or No: 
Yes
Points: 
1
Confidence Level: 
Very High
Answer / Justification: 
This plant is solidly, in the literature associated with wetlands and in New Zealand the seed is said to spread via water (NZPCN listing for L. junceum; Ertter & Gowen 2019).
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: 
Very Low
Answer / Justification: 
No specific pathway was documented in any source; only conjecture about machinery was mentioned.
Reference(s): 
Evaluation Notes

New Zealand Plant Conservation Network: https://www.nzpcn.org.nz/flora/species/lythrum-junceum/. Accessed 10/1/2021

GBIF: https://www.gbif.org/species/3988701. Accessed 10/1/2021

Kew Seed Information Database: http://data.kew.org/sid/SidServlet?ID=43457&Num=6NU. Accessed 10/1/2021

Total PRE Score

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

PRE Score: 
17
Number of questions answered: 
19
Screener Confidence (%): 
61.0
PRE Content Access and Privacy
Organization: 
California Invasive Plant Council (Cal-IPC)
PlantRight
2021 Western IPM Grant Project
Evaluation visibility: 
Public - accessible to all site users

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