Phytolacca americana -- Washington

Evaluation Summary

photo by Ron Vanderhoff, Orange County CNPS

Evaluation Date: 2022-09-28

Screener: Jim Evans

Plant: Phytolacca americana

Common Name(s):

American pokeweed, pigeonberry, pokeroot, inkberry coakum

State: Washington

PRE Score: 15

Questions Answered: 20

Screener Confidence (%): 90

Executive Summary

Phytolacca americana (common pokeweed) is a large (to 7m tall), taprooted perennial herb characteristic of open, disturbed places. Native to the southeastern United States, the species has become established in disturbed habitats in the eastern and midwestern U.S. and along the Pacific Coast of the U.S., persisting in some habitats. It is also naturalized in parts of South America, Africa, Asia, and throughout Europe. P. americana is autogamous (capable of self-pollination) and is a prolific producer of seeds which can remain viable in the soil for decades. Although consumed within its native range, all parts of the plant, but especially the roots and seeds, contain toxins that are poisonous to humans and other mammals when ingested without careful preparation.

Phytolacca americana may be troublesome weed in some agricultural situations. In natural areas it seldom forms large or dense infestations and seldom persists away from frequently disturbed places. In the Pacific Northwest P. americana appears to pose only a moderate risk as an invasive species.

Climate Matching Map

Climate Matching Map PDF

Attachment	Size
ClimateMatch_WA_Phytolacca_americana.pdf (1.22 MB)	1.22 MB

1. Question 1

Yes or No

Yes

Points

1

Confidence

Very High

Answer / Justification

Phytolacca americana (common pokeweed) is widely naturalized. Native to the southeastern United States, the species is naturalized in more than 30 counties in California (Calflora 2022), throughout Europe (PlantRight climate match, Invasoras.pt), in Central and South America, East Asia, and elsewhere (PlantRight climate match).

Reference(s)

“Phytolacca Americana L. ; American Pokeweed, Pokeberry”. n.d. Berkeley, CA: The Calflora Database. https://www.calflora.org/app/taxon?crn=6491.

“Phytolacca Americana”. 2017. Plataforma de informa\c c\~ao e ci\^encia-cidad\~a sobre plantas invasoras em Portugal. https://www.invasoras.pt/en/invasive-plant/phytolacca-americana.

“PlantRight”. n.d. http://websites.greeninfo.org/plantright/finder/$\#$.

2. Question 2

Yes or No

Yes

Points

2

Confidence

Very High

Answer / Justification

The species distribution along the west coast and fringes of the Appalachian chain lies in areas of similar climate to Washington and the Pacific Northwest, as does its distribution throughout most of Europe. (PlantRight climate match).

Reference(s)

“PlantRight”. n.d. http://websites.greeninfo.org/plantright/finder/$\#$.

3. Question 3

Yes or No

Yes

Points

2

Confidence

High

Answer / Justification

P. americana is considered invasive in Portugal, where it inhibits the development of native vegetation (Invasoras.pt). In California the species is listed as ‘Limited’ – invasive. but current information indicates their ecological impacts are minor on a statewide level but the species may be locally persistent and problematic (California Invasive Plant Council no date).

Reference(s)

“Phytolacca Americana”. 2007 2022. Berkeley, CA: California Invasive Plant Council. https://www.cal-ipc.org/plants/profile/phytolacca-americana-profile/.

“Phytolacca Americana”. 2017. Plataforma de informa\c c\~ao e ci\^encia-cidad\~a sobre plantas invasoras em Portugal. https://www.invasoras.pt/en/invasive-plant/phytolacca-americana.

4. Question 4

Yes or No

Yes

Points

3

Confidence

High

Answer / Justification

Areas where P. americana is considered invasive and which match Washington’s climate include California and Portugal (California Invasive Plant Council, Invasoras.pt, PlantRight Climate Match).

Reference(s)

“Phytolacca Americana”. 2007 2022. Berkeley, CA: California Invasive Plant Council. https://www.cal-ipc.org/plants/profile/phytolacca-americana-profile/.

“Phytolacca Americana”. 2017. Plataforma de informa\c c\~ao e ci\^encia-cidad\~a sobre plantas invasoras em Portugal. https://www.invasoras.pt/en/invasive-plant/phytolacca-americana.

“PlantRight”. n.d. http://websites.greeninfo.org/plantright/finder/$\#$.

5. Question 5

Yes or No

No

Points

0

Confidence

Very High

Answer / Justification

Neither the Invasive Plant Atlas of the United States nor the Global Invasive Species Database lists another species of Phytolacca nor any species in the Phytolaccaceae. Mexican pokeweed (Phytolacca heterotepala), a native of Central and South America, is A-listed (“pests of the agricultural industry or environment which score high and are not known to occur or under official control in the State of California)” by the California Department of Food and Agriculture (Randhawa 2018) but does not occur in a climate similar to the Pacific Northwest (PlantRight climate matching results for Phytolacca heterotepala).

Reference(s)

“Herbs/Forbs:/Invasive/Plant/Atlas/of/the/United/States”. n.d. https://www.invasiveplantatlas.org/herbs.html.

“Global Invasive Species Database”. 2022. International Union for the Conservation of Nature. http://www.iucngisd.org/gisd/search.php.

Randhawa, R. 2018. “Mexican Pokeweed | Phytolacca Heterotepala H. Walter” 2022. Sacramento, CA: California Department of Food and Agriculture. https://blogs.cdfa.ca.gov/Section3162/?p=4923.

“PlantRight”. n.d. http://websites.greeninfo.org/plantright/finder/$\#$.

6. Question 6

Yes or No

No

Points

0

Confidence

Very High

Answer / Justification

Major portions of P. americana’s range lie outside of areas with climate similar to Washington. These areas include the species’ native range in the southeastern U.S., the Eastern Seaboard, the midwestern U.S., the east coast of South America, eastern Europe, and China and Southeast Asia (PlantRight Climate Match).

Reference(s)

“PlantRight”. n.d. http://websites.greeninfo.org/plantright/finder/$\#$.

7. Question 7

Yes or No

No

Points

0

Confidence

High

Answer / Justification

Sellers et al. (2013) state that P. americana “rarely infests large areas,” except in agricultural fields.

Reference(s)

Sellers, B, P Devkota, and J Ferrell. 2013. “Common Pokeweed” 2022. Gainesville, FL: Agronomy Depertment, University of Florida IFAS Extension. https://edis.ifas.ufl.edu/pdf\%5CAG\%5CAG254\%5CAG254-2638922.pdf.

8. Question 8

Yes or No

No

Points

0

Confidence

High

Answer / Justification

P. americana exhibited an increase in cover from near 0% up to 5% following fire in pine forests in Michigan (Gucker 2005) and fire was judged important in recruitment for the species in deciduous forest in Ohio (Smith 2010). However, the species’ response was small relative to the overall composition of the plant communities studied, and none of the literature reviewed for this evaluation suggested that P. americana has a significant effect on fire regimes.

Reference(s)

Gucker, C. 2005. “Research Project Summary: Effects of Surface Fires in a Mixed Red and Eastern White Pine Stand in Michigan” 2022. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. www.fs.usda.gov/database/feis/research_project_summaries/Neumann01/all.html.

Smith, J. 2010. “Research Project Summary: Effects of Experimental Burning on Understory Plants in a Temperate Deciduous Forest in Ohio”. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. https://www.fs.usda.gov/database/feis/research_project_summaries/Glasgow07/all.html.

9. Question 9

Yes or No

Yes

Points

1

Confidence

Very High

Answer / Justification

Although people in the southeastern U.S. have traditionally harvested and eaten the shoots and leaves of P. americana (after careful preparation), all parts of the plant contain toxins, capable of causing illness and, in rare cases, death to humans, livestock, and other mammals. The greatest concentrations of toxins are in the roots and seeds (Sellers et al. 2013, Thieret 2012).

Reference(s)

Sellers, B, P Devkota, and J Ferrell. 2013. “Common Pokeweed” 2022. Gainesville, FL: Agronomy Depertment, University of Florida IFAS Extension. https://edis.ifas.ufl.edu/pdf\%5CAG\%5CAG254\%5CAG254-2638922.pdf.

Thieret, J. 2012. “Phytolacca Americana Var. Americana” 2022. Jepson Flora Project. https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=63756.

10. Question 10

Yes or No

No

Points

0

Confidence

High

Answer / Justification

Since the species seldom infests large areas it is unlikely to form stands that impede the movement of animals, livestock, or humans

Reference(s)

Sellers, B, P Devkota, and J Ferrell. 2013. “Common Pokeweed” 2022. Gainesville, FL: Agronomy Depertment, University of Florida IFAS Extension. https://edis.ifas.ufl.edu/pdf\%5CAG\%5CAG254\%5CAG254-2638922.pdf.

11. Question 11

Yes or No

No

Points

0

Confidence

High

Answer / Justification

The USDA Plants Database rates P. americana’s vegetative spread rate as “None.”

Reference(s)

“Phytolacca Americana L”. 2022. Washington D.C.: U.S. Department of Agriculture. https://plants.usda.gov/home/plantProfile?symbol=PHAM4.

12. Question 12

Yes or No

No

Points

0

Confidence

High

Answer / Justification

Naturally detached fragments of P. americana do not produce new plants.

Reference(s)

“Phytolacca Americana L”. 2022. Washington D.C.: U.S. Department of Agriculture. https://plants.usda.gov/home/plantProfile?symbol=PHAM4.

13. Question 13

Yes or No

Yes

Points

1

Confidence

Very High

Answer / Justification

Orock (2005) reported that, on average, 96.4% of P. americana seed in bird-consumed samples were viable and 97% of seeds in control samples were viable.

Reference(s)

Orock, J. 2005. “The Effect of Gut Passage by Two Species of Avian Frugivore on Seeds of Pokeweed, Phytolacca Americana”. Canadian Journal of Botany 83: 427-31.

14. Question 14

Yes or No

Yes

Points

1

Confidence

Very High

Answer / Justification

Armesto et al. (1983) reported averages of approximately 9.7 seeds/fruit, 58 fruits/raceme, and 2.7 racemes/plant for a total of approximately 1500 seeds/ plant in a wild population of P. americana in the eastern U.S. Sellers et al. (2013) reported that individual plants are capable of producing over 48,000 seeds, though the authors do not provide data or a citation supporting this assertion.

Reference(s)

Armesto, J., G Cheplick, and M McDonnell. 1893. “Observations on the Reproductive Biology of Phytolacca Americana (Phytolaccaceae)”. Bulletin of the Torrey Botanical Club 110: 380-83.

Sellers, B, P Devkota, and J Ferrell. 2013. “Common Pokeweed” 2022. Gainesville, FL: Agronomy Depertment, University of Florida IFAS Extension. https://edis.ifas.ufl.edu/pdf\%5CAG\%5CAG254\%5CAG254-2638922.pdf.

15. Question 15

Yes or No

Yes

Points

1

Confidence

Very High

Answer / Justification

Several laboratory studies have reported germination rates of P. americana not lower than 25% and mostly between 80-99% (Armesto et al. 1983, Orock 2005).

Reference(s)

No references cited.

16. Question 16

Yes or No

Yes

Points

1

Confidence

High

Answer / Justification

Patches (2014) reported that, during both years of a two-year field study in Pennsylvania, spring-emergent seedlings of P. americana produced mature fruits and seeds by the end of their first growing season.

Reference(s)

Patches, K. (2014) 2014. “Common Pokeweed (Phytolacca Americana L.) Management in Pennsylvania Field Crops.”

17. Question 17

Yes or No

Yes

Points

1

Confidence

Very High

Answer / Justification

Although Calflora reports the bloom period in California as two months (July-August) Armesto et al. (1983) and McDonnell et al. (1984) report flower and fruit production lasting from early summer through late fall in the species native range in the eastern U.S. In Portugal the species reportedly blooms from May to December (Invasoras.pt 2017).

Reference(s)

McDonnell, M, E Stiles, G Cheplick, and J Armesto. 1984. “Bird-Dispersal of Phytolacca Americana L. And the Influence of Fruit Removal on Subsequent Development”. American Journal of Botany 71: 895-901.

Armesto, J., G Cheplick, and M McDonnell. 1893. “Observations on the Reproductive Biology of Phytolacca Americana (Phytolaccaceae)”. Bulletin of the Torrey Botanical Club 110: 380-83.

“Phytolacca Americana L. ; American Pokeweed, Pokeberry”. n.d. Berkeley, CA: The Calflora Database. https://www.calflora.org/app/taxon?crn=6491.

“Phytolacca Americana”. 2017. Plataforma de informa\c c\~ao e ci\^encia-cidad\~a sobre plantas invasoras em Portugal. https://www.invasoras.pt/en/invasive-plant/phytolacca-americana.

18. Question 18

Yes or No

Yes

Points

1

Confidence

Very High

Answer / Justification

Birds, unaffected by the toxicity of P. americana, consume the species’ fleshy fruits and are the principal agents of seed dispersal for P. americana (McDonnell et al. 1984, Orock 2005).

Reference(s)

No references cited.

19. Question 19

Yes or No

No

Points

0

Confidence

High

Answer / Justification

None of the available literature mentions wind or water as means of dispersal for P. americana. Birds are the principal agents of dispersal (McDonnell et al. 1984, Orock 2005).

Reference(s)

No references cited.

20. Question 20

Yes or No

No

Points

0

Confidence

High

Answer / Justification

None of the available literature suggests that these vectors are frequent means of dispersal for P. americana.

Reference(s)

No references cited.

Total PRE Score

PRE Score

15

Questions Answered

20

Screener Confidence (%)

90

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: Jim Evans

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

Evans, Jim. "Phytolacca americana -- Washington" Plant Risk Evaluator (PRE) published 2022-09-28 https://pretool.org/evaluations/1795

Please cite this evaluation. We need your support here!

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Evaluation Reviewers

		reviewed on 2022-10-24
	Jutta Burger	reviewed on 2022-10-23
	Alex Simmons	reviewed on 2022-10-12

Associated Project

2022 Western IPM Grant Project

"Expanding Continuity and Capacity in Invasive Plant Risk Assessments across Western States" is a continuation of the successful 2021 project titled "Building Continuity Across State Invasvie Plant Lists: Evaluating Invasive Risk of Horticultural Plants." Both 2021 and 2022's projects are funded by the Western Integrated Pest Management Center. Project partners for this year inclue the California Invasive Plant Council, PlantRight, The University of Arizona, Western Invasive Species Network, Pacific Northwest Invasive Species Council, the Yurok Tribe, and Nevada State Parks.

Associated Organizations, Agencies, and Institutions

Pacific Northwest Invasive Plant Council