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PRE — Plant Risk Evaluator

Euphorbia dentata -- Oregon

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Evaluation Summary


Euphorbia dentata photo by Max Licher

Evaluation Date:  2025-03-05

Screener:  Courtney Gattuso
 
Plant:  Euphorbia dentata
Common Name(s):
toothed spurge, toothed Euphorbia, green poinsettia

State:  Oregon

PRE Score:  12
Questions Answered:  20
Screener Confidence (%):  67

Executive Summary

Euphorbia dentata (toothed spurge) has naturalized in some regions outside its native range, including parts of Europe and the U.S., but is not widely classified as invasive. It is considered invasive in certain areas, such as China and parts of the U.S., though not specifically in the Pacific Northwest. The plant does not form impenetrable thickets but may impact native vegetation in some regions. It reproduces exclusively by seed, producing viable seeds annually, but does not spread vegetatively or via detached fragments. While exact seed production numbers are unclear, it likely produces large quantities of viable seeds and does not require special conditions for germination. Seeds are dispersed locally through explosive dehiscence but are not frequently carried long distances by wind, water, or animals. However, human activities such as contaminated equipment, vehicles, and clothing may contribute to its spread. The plant's toxic sap poses risks to humans and livestock, potentially impacting grazing systems. Overall, E. dentata has the potential to establish and spread but lacks some of the most aggressive traits of highly invasive species.

Climate Matching Map

Attachment Size
climatematch-euphorbia_dentata-oregon-20250305.pdf (1.12 MB) 1.12 MB

1. Question 1

Yes
1
High
Euphorbia dentata, commonly known as toothed spurge, is native to parts of North and South America, specifically from northern Mexico and the south-central United States north and east through the Ohio River Valley. However, it has become naturalized in regions outside its native range. For instance, in New England, it is absent except for an introduced occurrence in northern Vermont. Additionally, Euphorbia dentata is present in Europe, indicating its naturalization beyond its native habitat.
“Euphorbia Dentata - Toothed Spurge”. 1729. https://gobotany.nativeplanttrust.org/species/euphorbia/dentata/.
“Euphorbia Dentata”. 1729. SEINet Portal Network - Arizone/New Mexico Chapter. https://swbiodiversity.org/seinet/taxa/index.php?taxon=euphorbia+dentata.
Garcke, Klotzsch \&. 1803. “Euphorbia Dentata (Flora of North America)”. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242321404.

2. Question 2

Yes
2
High
There are occurrences of toothed spurge in the Pacific Northwest (Idaho, Oregon, and Utah) and many observations in the Appalachian region of the eastern United States. The Climate Matching Map shows Euphorbia dentata's potential to naturalize in areas outside of its native range due to the high volume of documented observations.
“Euphorbia Dentata Michx”. 1729. https://www.gbif.org/species/3066993.

3. Question 3

Yes
2
Medium
While it has become naturalized in regions beyond its native range, it is not widely recognized as an invasive species in the United States. For example, the USDA Plants Database does not list it as invasive or noxious. However, in Idaho, it is classified as a noxious weed due to its potential adverse impacts. In China, E. dentata is considered invasive and is known for its toxicity and potential to reduce crop yields.
“Euphorbia Dentata Michx”. 1729. https://plants.usda.gov/plant-profile/EUDE4.
Xu, Chen-Sen, and Zhi-Xin Liao. (2024) 2024. “Dentatacid A: An Unprecedented 2, 3-Seco-Arbor-2, 3-Dioic Triterpenoid from the Invasive Plant Euphorbia Dentata, With Cytotoxicity Effect on Colon Cancer”. Edited by Yuan-Ling Shao, Qing Li, and Hong-Wei Wu. Multidisciplinary Digital Publishing Institute (MDPI). https://pmc.ncbi.nlm.nih.gov/articles/PMC11397642/$\#$abstract1.

4. Question 4

Yes
3
Medium
Several states recognize toothed spurge as an introduced species, but few deem it an invasive or noxious. The Colorado State University Extension considers E. dentata an invasive weed, though it is not officially listed as a noxious weed in the state. They recommend removing it from gardens to prevent its spread. The species has been reported in countries such as Switzerland and France, primarily in railway areas. While many populations are small and confined to these disturbed sites, E. dentata has shown the ability to invade agricultural fields, raising concerns about its potential impact on crop yields. Its known distribution has locations with a similar climates to Oregon.
“Wild Poinsettia - Euphorbia Dentata - Invasive? Should I Pull Them Out of My Englewood Garden?”. 1729. https://ask2.extension.org/kb/faq.php?id=765296.
Barina, Zolt\ an, Myroslav Shevera, Culi\c t\u a S\^\irbu, and Gyula Pinke. 2013. “Current Distribution and Spreading of Euphorbia Davidii (E. Dentata Agg.) in Europe”. Central European Journal of Biology 8. https://www.researchgate.net/publication/260842898_Current_distribution….

5. Question 5

Yes
1
Very High
Several species within the Euphorbia genus, as well as closely related genera, are recognized as invasive in climates similar to the Pacific Northwest. In Oregon alone, there are 3 Euphorbia spp. that are listed on the state noxious weed list: Oblong spurge
(Euphorbia oblongata), Mytle spurge (Euphorbia myrsinities), and Leafy spurge (Euphorbia esula).
“Oregon Noxious Weed Profiles”. 1729. https://www.oregon.gov/oda/weeds/oregon-noxious-weeds/pages/default.aspx.

6. Question 6

No
0
High
The majority of toothed spurge occurrences are found predominately in climates that do not match Oregon's. Therefore, it has the ability to thrive in several different climate types.
“Euphorbia Dentata Michx”. 1729. https://www.gbif.org/species/3066993.

7. Question 7

No
0
Low
Toothed spurge has been observed to impact native plant communities in certain regions where it has been established. However, specific information regarding its ability to displace native plants and dominate plant communities is limited. Studies in China and Europe show that it has an invasive potential with a growing number of established populations, and encourages close monitoring, especially in agricultural settings.
Xu, Chen-Sen, and Zhi-Xin Liao. (2024) 2024. “Dentatacid A: An Unprecedented 2, 3-Seco-Arbor-2, 3-Dioic Triterpenoid from the Invasive Plant Euphorbia Dentata, With Cytotoxicity Effect on Colon Cancer”. Edited by Yuan-Ling Shao, Qing Li, and Hong-Wei Wu. Multidisciplinary Digital Publishing Institute (MDPI). https://pmc.ncbi.nlm.nih.gov/articles/PMC11397642/$\#$abstract1.
Barina, Zolt\ an, Myroslav Shevera, Culi\c t\u a S\^\irbu, and Gyula Pinke. 2013. “Current Distribution and Spreading of Euphorbia Davidii (E. Dentata Agg.) in Europe”. Central European Journal of Biology 8. https://www.researchgate.net/publication/260842898_Current_distribution….

8. Question 8

No
0
Medium
​Currently, there is no specific evidence indicating that Euphorbia dentata (toothed spurge) promotes fire or alters fire regimes in areas where it has been established.
No references cited.

9. Question 9

Yes
1
Very High
The plant contains a milky sap that is toxic upon contact or ingestion. Exposure can lead to skin irritation, blisters, and dermatitis. If the sap comes into contact with the eyes, it may cause temporary blindness. The toxic sap can cause adverse effects in livestock, including cattle and horses, leading to symptoms such as vomiting, diarrhea, and mouth irritation.
“Weed of the Month: Toothed Spurge (Euphorbia Dentata)”. 1729. https://ipm.missouri.edu/croppest/2014/7/Weed-of-the-Month-Toothed-Spur….

10. Question 10

No
0
High
It generally grows between 8 to 24 inches high and does not form dense thickets. Therefore, it is unlikely to impede or slow the movement of animals, livestock, or humans in areas where it has been established.
“Euphorbia Dentata”. 1729. SEINet Portal Network - Arizone/New Mexico Chapter. https://swbiodiversity.org/seinet/taxa/index.php?taxon=euphorbia+dentata.

11. Question 11

No
0
Very High
​Euphorbia dentata (toothed spurge) reproduces exclusively by seed and does not spread vegetatively. This reproductive strategy involves the production of seeds following flowering, without the formation of bulbils or other vegetative structures for propagation.
“Euphorbia Dentata - Toothed Spurge”. 1729. https://gobotany.nativeplanttrust.org/species/euphorbia/dentata/.

12. Question 12

No
0
High
Since toothed spurge does not reproduce vegetatively, it cannot spread via detached fragments.
No references cited.

13. Question 13

Yes
1
High
Euphorbia dentata (toothed spurge) commonly produces viable seeds. As an annual plant, it relies on seed production for reproduction and propagation. The seeds typically germinate when temperatures become warm, allowing the species to establish itself in suitable habitats.
“Toothed Spurge”. 1729. https://www.illinoiswildflowers.info/prairie/plantx/tooth_spurgex.htm.

14. Question 14

No
0
Very Low
I could not find any references that estimated seed production.
No references cited.

15. Question 15

No
0
Very Low
I could not find enough information to support a significant germination rate for Euphorbia dentata.
No references cited.

16. Question 16

Yes
1
Very High
It is an annual herbaceous species, meaning it completes its life cycle—including germination, growth, flowering, and seed production—within a single growing season. Since it does not persist beyond one year, it must produce viable seeds within its first year to ensure future generations.
“Know Your Natives - Toothed Spurge”. 1729. https://anps.org/2020/10/08/know-your-natives-toothed-spurge/.
“Toothed Spurge”. 1729. https://www.illinoiswildflowers.info/prairie/plantx/tooth_spurgex.htm.

17. Question 17

No
0
Very High
Toothed spurge typically blooms in mid-summer, with the blooming period lasting about one month. This suggests that seed production occurs once per year during this blooming period and does not extend continuously for more than three months.
“Weed of the Month: Toothed Spurge (Euphorbia Dentata)”. 1729. https://ipm.missouri.edu/croppest/2014/7/Weed-of-the-Month-Toothed-Spur….

18. Question 18

No
0
Low
Toothed spurge primarily disperses its seeds through explosive dehiscence, a mechanism where mature fruiting capsules forcibly eject seeds to nearby areas. This method typically results in seed dispersal over relatively short distances.​ There is no evidence to suggest that its seeds are frequently dispersed over long distances by mammals, birds, or domestic animals.
“Know Your Natives - Toothed Spurge”. 1729. https://anps.org/2020/10/08/know-your-natives-toothed-spurge/.

19. Question 19

No
0
Low
There is no evidence to suggest that E. dentata seeds are adapted for long-distance dispersal by wind or water. Therefore, it is unlikely that the plant's propagules are frequently dispersed over distances greater than 100 meters by these means.
No references cited.

20. Question 20

No
0
Very Low
While specific studies on E. dentata are limited, these general dispersal mechanisms have been documented in related species. For instance, Euphorbia esula (leafy spurge) seeds are known to disperse via vehicles, equipment, and contaminated soil and can spread along roadways and into agricultural and natural areas. Therefore, it is plausible that E. dentata propagules can be dispersed over long distances through similar means, particularly when human activities inadvertently transport seeds attached to equipment, vehicles, or clothing.​
“Leafy Spurge”. 1729. https://www.mda.state.mn.us/plants/pestmanagement/weedcontrol/noxiousli….

Total PRE Score

12
20
67

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:  Courtney Gattuso

 

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

Gattuso, Courtney. "Euphorbia dentata -- Oregon" Plant Risk Evaluator (PRE) published 2025-03-05 https://pretool.org/evaluations/4949

 


Please cite this evaluation. We need your support here!

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Evaluation Reviewers

Troy Abercrombie reviewed on 2025-04-17
Jutta Burger reviewed on 2025-03-18
Nicole Valentine reviewed on 2025-03-12

 

Associated Project

2023-2025 Western IPM Project

This project intends to support the expanded use of the online PRE tool to more Western States and nations, and to explore the use of the PRE results for each partner region. Along with the direct benefit from the plant assessments, this project will also provide a platform through which to collaborate on a range of efforts related to preventing introduction of invasive plants through horticulture. Each partner can share their expertise on effort such as providing information on safe landscaping alternatives, surveying nurseries for data on what is being sold, comparing species priorities.

 

Associated Organizations, Agencies, and Institutions

Cascade Pacific Resource Conservation & Development

 

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