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PRE — Plant Risk Evaluator

Lathyrus latifolius -- California

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Evaluation Summary


photo by Ron Vanderhoff

Evaluation Date:  2020-02-10

Screener:  Lynn Sweet
 
Plant:  Lathyrus latifolius
Common Name(s):
Perennial sweet pea

State:  California

PRE Score:  16
Questions Answered:  20
Screener Confidence (%):  70

Executive Summary

This plant is a vining perennial with an extensive history in the horticultural industry. It has naturalized throughout the US, and also in Australia and beyond its native range (North Africa/Southern Europe) into Eastern and Northern Europe. The plant is noted as producing monocultures and invading natural areas. However it is heavily associated with disturbed sites and roadsides. It can reproduce by seed but its persistence onsite is due to its extensive production of rhizomes, making it very difficult to control once established.

Climate Matching Map

https://weedmap.cal-ipc.org/climatematch/?areaType=states&areaList%5B0%5D=06&ma…
Attachment Size
climatematch-lathyrus_latifolius-california-20251029.pdf (1.17 MB) 1.17 MB

1. Question 1

Yes
1
Very High
The species has naturalized where it is not native in the eastern Mediterranean region (Cyprus), Northern and central Europe, Australia, and North America.
NPGS, USDA-ARS. 2020. “Germplasm Resources Information Network (GRIN-Taxonomy)”. https://npgsweb.ars-grin.gov/gringlobal/taxonomydetail.aspx?id=21580 .

2. Question 2

Yes
2
Very High
Yes. The species has naturalized in 43 counties in the region of interest, California, USA. (Calflora)
As well, the species is naturalized in Oregon and Washington, which have a similar climate.
Calflora. 2016. “Calflora California Wild Plant Database”. Berkeley, California: The Calflora Database [a non-profit organization]. http://www.calflora.org/.

3. Question 3

Yes
2
High
The plant is listed as being invasive in many areas of the US, primarily referencing roadsides and rights-of-way (Oregon Dept of Ag).
Considered to be invasive in some areas in the US (Missouri Botanical Garden)
The plant is an environmental weed in Victoria, Australia and on Lord Howe Island, it is listed as an invasive plant that is targeted for eradication. (Weeds of Australia)
This was noted as late-season monoculture in the San Francisco area. (R. Kesel, Pers. Comm.)
Agriculture, Oregon Dept of. 2020. “Oregon Department of Agriculture ‘B’ Rated Weeds: Perennial Peavine”. https://www.oregon.gov/oda/Documents/Publications/Weeds/PerennialPeavin….
“Missouri Botanical Garden Plant Finder”. 2014. http://www.missouribotanicalgarden.org/plantfinder/plantfindersearch.as….
Government, Queensland. 2020. “Lathyrus Latifolius Fact Sheet from Environmental Weeds of Australia for Biosecurity Queensland Edition”. https://keyserver.lucidcentral.org/weeds/data/media/Html/lathyrus_latif….
Kesel, Rachel. 2019. “Personal Communication, Rachel Kesel, OneTam Conservation Mgmt Specialist.”

4. Question 4

Yes
3
High
Within the region of interest, this was noted as becoming a late-season monoculture in urban areas around San Francisco, and it has been managed in another disturbed preserve in San Francisco. It was also noted that it demonstrates an extremely extensive rhizome network. The plant occurs in the front country of Mt. Tamalpais, Dipsea area, and several highway corridors in Sonoma County (R. Kesel, Pers. Comm.)
Within a similar climate, the plant is listed as being invasive in Oregon, primarily referencing roadsides and rights-of-way (Oregon Dept of Ag).
Although it is noted that it is mainly a weed of disturbed sites and roadsides where it occurs in Australia, they do mention that it has invaded natural areas as well. The plant is listed as being invasive in Victoria, Australia, some of which matches the climate in California. (Weeds of Australia, Queensland)
Kesel, Rachel. 2019. “Personal Communication, Rachel Kesel, OneTam Conservation Mgmt Specialist.”
Government, Queensland. 2020. “Lathyrus Latifolius Fact Sheet from Environmental Weeds of Australia for Biosecurity Queensland Edition”. https://keyserver.lucidcentral.org/weeds/data/media/Html/lathyrus_latif….
Agriculture, Oregon Dept of. 2020. “Oregon Department of Agriculture ‘B’ Rated Weeds: Perennial Peavine”. https://www.oregon.gov/oda/Documents/Publications/Weeds/PerennialPeavin….

5. Question 5

No
0
Low
Lathyrus odoratus is noted to be invasive in New Zealand and possibly in the Dominican Republic (CABI). This species has naturalized in California but no information was available about it being invasive.
No other Lathyrus are on the noxious weed list in the region of interest.
Rojas-Sandoval, Julissa. 2007. “CABI Invasive Species Compendium”. https://www.cabi.org/.

6. Question 6

No
0
Medium
The plant is found throughout vast areas of the United States, much of which does not match the region of concern. The areas where it is found in Central, Eastern and Northern Europe and Scandinavia do not match the region of concern. Of the areas reported in Australia and New Zealand, about half of the areas match the climate in the region of concern. (GBIF, Invasive Plants Atlas)
Secretariat, GBIF. 2016. “GBIF Backbone Taxonomy”. http://www.gbif.org/dataset/d7dddbf4-2cf0-4f39-9b2a-bb099caae36c.
Swearingen, J, and C. Bargeron. 2020. “Everlasting Peavine Lathyrus Latifolia: Invasive Plant Atlas of the United States”. University of Georgia Center for Invasive Species and Ecosystem Health. https://www.invasiveplantatlas.org/subject.html?sub=5912.

7. Question 7

Yes
1
High
In Oregon, USA, the plant is known to overtop and smother native vegetation.
Agriculture, Oregon Dept of. 2020. “Oregon Department of Agriculture ‘B’ Rated Weeds: Perennial Peavine”. https://www.oregon.gov/oda/Documents/Publications/Weeds/PerennialPeavin….

8. Question 8

No
0
Medium
No effects noted having to do with fire. The plant is a low-growing tender perennial, so unlikely to contribute to fire risk substantially.
No references cited.

9. Question 9

Yes
1
High
Can be toxic to livestock. (DiTomaso et al)
USDA GRIN lists it as a vertebrate poison for mammals.
DiTomaso, Joseph M., and Evelyn A. Healy. 2013. Weed Control in Natural Areas in the Western United States. Davis, CA: University of California, Weed Research and Information Center.
, Agricultural Resource Service, and National Plant Germplasm System. 2020. “Germplasm Resources Information Network (GRIN Taxonomy)”. https://npgsweb.ars-grin.gov/gringlobal/taxon/taxonomydetail?id=16358.

10. Question 10

No
0
Medium
The plant grows tender foliage and flowers to 4-8" tall, so this is unlikely.
“Missouri Botanical Garden Plant Finder”. 2014. http://www.missouribotanicalgarden.org/plantfinder/plantfindersearch.as….

11. Question 11

Yes
1
Very High
Rhizomatous growth is a well-known method of reproduction for this species.
“Missouri Botanical Garden Plant Finder”. 2014. http://www.missouribotanicalgarden.org/plantfinder/plantfindersearch.as….

12. Question 12

Yes
1
Low
Since this is a vining species, it is likely that animals moving through the underbrush could easily detach pieces of the vine and deposit them elsewhere, however, this was not noted in any reference.
Hossaert-McKey, M., and M. Jarry. 1992. “Spatial and Temporal Patterns of Investment in Growth and Sexual Reproduction in Two Stoloniferous Species, Lathyrus Latifolius and L. Sylvestris”. Journal of Ecology 80: 555\textendash565. doi:10.2307/2260698.

13. Question 13

Yes
1
High
The plant is said to easily self-seed.
“Missouri Botanical Garden Plant Finder”. 2014. http://www.missouribotanicalgarden.org/plantfinder/plantfindersearch.as….

14. Question 14

No
0
Medium
The primary means of reproduction appears to be vegetative. It was noted that seeds were rarely set in greenhouse settings, and seed set in the field is very dependent on pollinators and the abundance of nectar robbers (Godt & Hamrick 1992).
The number of ramets in the field far exceeded the number of seedlings. (Hossaert-McKey and Jarry 1992)
A study of ovule position in natural populations in Europe showed some variation, but note an average of 10-12 flowers per inflorescence, maturing 0.5-1.5 pods each, and an average of 5-6 viable seeds per pod. This source did not mention the number of infl. per individual, but the numbers would likely be less than 1000 seeds per individual. (Hossaert & Valero 1988)
Godt, Mary Jo W., and J. L. Hamrick. 1991. “Estimates of Outcrossing Rates in Lathyrus Latifolius Populations”. Genome 34: 988\textendash992. doi:10.1139/g91-152.
Hossaert-McKey, M., and M. Jarry. 1992. “Spatial and Temporal Patterns of Investment in Growth and Sexual Reproduction in Two Stoloniferous Species, Lathyrus Latifolius and L. Sylvestris”. Journal of Ecology 80: 555\textendash565. doi:10.2307/2260698.
Hossaert-McKey, Martine, and Myriam Valero. 1988. “Effect of Ovule Position in the Pod on Patterns of Seed Formation in Two Species of Lathyrus (leguminosae: Papilionoideae)”. American Journal of Botany 75 (11): 1714-31. doi:10.1002/j.1537-2197.1988.tb11248.x.

15. Question 15

Yes
1
High
There was no mention of specific requirements for germination. Germination rates were listed as high under various conditions listed in Kew Seed Information Database.
Kew, Royal Botanic Gardens. 2016. “Kew Seed Information Database”. Kew Royal Botanic Gardens. http://data.kew.org/sid/.

16. Question 16

Yes
1
Medium
The species didn't flower the first year under controlled conditions in a study that also showed high mortality, so this is probably not typical (Hossaert-McKey & Jarry 1992).
The plant is listed in garden blogs/web sales as flowering during the first year, and also unlikely to flower in the first year. None indicated that it would take longer than 3 years for the plant to flower.
Hossaert-McKey, M., and M. Jarry. 1992. “Spatial and Temporal Patterns of Investment in Growth and Sexual Reproduction in Two Stoloniferous Species, Lathyrus Latifolius and L. Sylvestris”. Journal of Ecology 80: 555\textendash565. doi:10.2307/2260698.
“Roger Parson’s Sweet Peas”. 2020. https://www.englishsweetpeas.co.uk/.

17. Question 17

Yes
1
High
Calflora lists the bloom period as May-September (5 months). Other garden sites list the species as blooming "all summer."
"The first flowers of both species appear in late June and early July, and the last pods mature in October. Each of the pink flowers ...stays open during about one week. Fertilized fruits require about one month for maturation." (Hossaert & Valero 1988)
No references cited.

18. Question 18

No
0
Low
Being fairly toxic to wildlife and with the evolution of a violent dehiscion and vegetative reproduction as dispersal, it's unlikely.
Burnham, Robyn J. 2013. “Censusing Lianas In Mesic Biomes of Eastern RegionS: Lathyrus Latifolius” 2020. http://climbers.lsa.umich.edu/?p=282.

19. Question 19

No
0
Medium
The large, heavy seeds are noted to be primarily gravity dispersed. (Godt and Hamrick 1991)
Godt, Mary Jo W., and J. L. Hamrick. 1991. “Estimates of Outcrossing Rates in Lathyrus Latifolius Populations”. Genome 34: 988\textendash992. doi:10.1139/g91-152.

20. Question 20

No
0
Medium
This is noted to be a roadside weed in Oregon, however, there is no specific mechanism of attachment to vehicles, and it is not noted to be an ag contaminant. Dehiscing violently and gravity seem to be the primary way the seeds disperse.
Burnham, Robyn J. 2013. “Censusing Lianas In Mesic Biomes of Eastern RegionS: Lathyrus Latifolius” 2020. http://climbers.lsa.umich.edu/?p=282.

Evaluation Notes

Newer climate match link and map added 10/31/25 but associated answers to questions were not re-reviewed (J. Burger)

Total PRE Score

16
20
70

PRE Score Legend

The PRE Score is calculated by adding the point totals for each (answered) question.

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

Questions Answered Legend

It is important to answer at least 16 questions to consider a PRE Score as "valid".

≥ 16 : Valid (80% or more questions answered)
≤ 15 : Invalid (not enough questions answered)

Evaluation Credits and Citation


Screener:  Lynn Sweet

 

Below is a recommend citation when referencing this evaluation in other works:

Sweet, Lynn. "Lathyrus latifolius -- California" Plant Risk Evaluator (PRE) published 2020-02-10 https://pretool.org/evaluations/1725

 


Please cite this evaluation. We need your support here!

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Evaluation Reviewers

Jutta Burger reviewed on 2025-10-31

 

Associated Project

There are no associated projects.


 

Associated Organizations, Agencies, and Institutions

PlantRight
California Invasive Plant Council (Cal-IPC)

 

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