Robert H. Mohlenbrock
USDA, NRCS 1995
Northeast Wetland Flora
@ USDA NRCS PLANTS
California Pest Rating for
Pickerelweed (Pontederia cordata L)
Pest Rating: D | Proposed Seed Rating: None
PEST RATING PROFILE
Pontederia cordata currently does not have a rating. It has recently been recommended by Project Plant Right and by the California Invasive Plant Council as a viable alternative for water hyacinth (Eichhornia crassipes) in water gardens. Reports that P. cordata may be spreading spontaneously in California have prompted this review (Kelch & Murdock, 2012).
History & Status:
Background: Pontederia cordata is a perennial, herbaceous, emergent aquatic plant native to the eastern United States. It has light green stems and leaves, and showy blue-violet flower spikes. The plant can reach four feet tall with the spike growing to six inches in length. Pontederia cordata typically grows in shallow water (not more than three feet deep), and inhabits marshes, bogs, and the margins of lakes and streams.
Worldwide Distribution: Pontederia cordata is native to Canada, Central America, Brazil, the West Indies and Argentina (Horn, 2002). It is naturalized in parts of Australia, Europe, and Africa. It is considered invasive in Kenya (BioNET-EAFRINET, 2011) and South Africa (Invasive Species South Africa, 2018). Pontederia cordata is native to the eastern United States. The native distribution of P. cordata is from Nova Scotia to Minnesota, south to Florida and Texas (NRCS, 2002).
Official Control: Pontederia cordata is officially a controlled weed in South Africa.
California Distribution: Pontederia cordata is not currently established in California. There have been occasional finds, but limited in scope. Currently these are interpreted as waifs.
California Interceptions: Pontederia cordata has collected a total of nine specimens in California. The Consortium of California Herbaria has records in Alameda, San Joaquin, Monterey, and Riverside counties.
The risk P. cordata would pose to California is evaluated below.
Consequences of Introduction
1) Climate / Host Interaction: Pontederia cordata prefers fresh, non-turbid water (Lougheed et al, 2001) which limits the areas of establishment. Risk is Medium (2), as cordata may be able to establish in fresh water areas, an uncommon habitat in much of California.
Evaluate if the pest would have suitable hosts and climate to establish in California. Score:
– Low (1) Not likely to establish in California; or likely to establish in very limited areas.
– Medium (2) may be able to establish in a larger but limited part of California.
– High (3) likely to establish a widespread distribution in California.
2) Host Range: Risk is High (3) as weeds do not require any one host, but grow wherever ecological conditions are favorable.
Evaluate the host range of the pest. Score:
– Low (1) has a very limited host range.
– Medium (2) has a moderate host range.
– High (3) has a wide host range.
3) Pest Dispersal Potential: Capers et al, 2009 reviewed the functional dispersal traits of aquatic plants and ranked cordata as a “Poorly dispersing species”. While this plant has the capability of reproducing sexually in its native range, it appears to be limited in other areas, including California, to vegetative reproduction by rhizome. Therefore, P. cordata receives a Low (1) in this category.
Evaluate the natural and artificial dispersal potential of the pest. Score:
– Low (1) does not have high reproductive or dispersal potential.
– Medium (2) has either high reproductive or dispersal potential.
– High (3) has both high reproduction and dispersal potential.
4) Economic Impact: Pontederia cordata can form patches which, if such patches developed in canals, could potentially interfere with water flow (Cichra, 2001). Pontederia cordata receives a Low (1) in this category.
Evaluate the economic impact of the pest to California using the criteria below.
Economic Impact: G
A. The pest could lower crop yield.
B. The pest could lower crop value (includes increasing crop production costs).
C. The pest could trigger the loss of markets (includes quarantines).
D. The pest could negatively change normal cultural practices.
E. The pest can vector, or is vectored, by another pestiferous organism.
F. The organism is injurious or poisonous to agriculturally important animals.
G. The organism can interfere with the delivery or supply of water for agricultural uses.
Economic Impact Score: 1
– Low (1) causes 0 or 1 of these impacts.
– Medium (2) causes 2 of these impacts.
– High (3) causes 3 or more of these impacts.
5) Environmental Impact: The vegetation and seeds are edible to wildlife (NRCS, 2002) and the plant is a good filtration plant for nitrates (Song et al, 2014). However, if cordata were to form large patches it could potentially interfere with water flow and trigger treatment programs. Therefore, P. cordata receives a Medium (2) in this category.
Evaluate the environmental impact of the pest on California using the criteria below.
Environmental Impact: D
A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.
B. The pest could directly affect threatened or endangered species.
C. The pest could impact threatened or endangered species by disrupting critical habitats.
D. The pest could trigger additional official or private treatment programs.
E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.
Score the pest for Environmental Impact. Score: 2
– Low (1) causes none of the above to occur.
– Medium (2) causes one of the above to occur.
– High (3) causes two or more of the above to occur.
Consequences of Introduction to California for P. cordata: Medium (9)
Add up the total score and include it here.
–Low = 5-8 points
–Medium = 9-12 points
–High = 13-15 points
6) Post Entry Distribution and Survey Information: Pontederia cordata is has only been detected sporadically in California. It receives a Not established (0) in this category.
Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.
–Not established (0) Pest never detected in California, or known only from incursions.
–Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).
–Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.
-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.
The final score is the consequences of introduction score minus the post entry distribution and survey information score: Medium (9)
The plant has been a popular aquatic landscaping plant for decades, but has not established itself as a pest. Uncertainty is Low.
Conclusion and Rating Justification:
Based on the score listed above the pest is low risk for further invasions of California. At this point a D rating is justifed.
BioNET-EAFRINET. 2011. “Keys and Fact Sheets: Pontederia cordata (Pickerel Weed). https://keys.lucidcentral.org/keys/v3/eafrinet/weeds/key/weeds/Media/Html/Pontederia_cordata_(Pickerel_Weed).htm Accessed: February 28, 2017
CalFlora: http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=9390 Accessed: February 28, 2017
Capers, R.S., Selsky, R. & Bugbee, G.J. 2009. “The relative importance of local conditions and regional processes in structuring aquatic plant communities”. Freshwater Biology. doi:10.1111/j.1365-2427.2009.02328.x
Cichra, C. 2001. “Physical and vegetative characteristics of floating islands”. J. Aquat. Plant Manage. 39:107-111. July 2001.
Consortium of California Herbaria: http://ucjeps.berkeley.edu/ Accessed: March 1, 2017
Horn, C.N. 2002. Pontederiaceae. In: Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 20+ vols. New York and Oxford. Vol. 26, pp. 45-46.
Invasive Species South Africa. 2018. Plants Search: Pickerel weed (Pontederia cordata). http://www.invasives.org.za/legislation/item/311-pickerel-weed-pontederia-cordata Accessed February 28, 2018
Kelch, D.G., Murdock, A., 2012. Flora of the Carquinez Strait Region, Contra Costa and Solano Counties, California. Madroño 59:47–108.
Long, R.W. & Lakela, O. 1976. A Flora of Tropical Florida: A Manual of the Seed Plants and Ferns of Southern Peninsular Florida, second edition. Banyon Books, Miami, Florida.
Lougheed, V.L., Crosbie, B. & Chow-Fraser, P. 2001. “Primary determinants of macrophyte community structure in 62 marshes across the Great Lakes basin: latitude, land use, and water quality effects”. Can. J. Fish. Aquat. Sci. 58:1603-1612.
Natural Resources Conservation Service. 2002. “Plant Fact Sheet: Pickerelweed (Pontederia cordata L.). United States Department of Agriculture https://plants.usda.gov/factsheet/pdf/fs_poco14.pdf Accessed February 28, 2018
Song, B., Mallin, M.A., Long, A., & McIver, M.R. 2014. “Factors controlling microbial Nitrogen removal efficacy in constructed stormwater wetlands”. Water Resources Research Institute of the University of North Carolina. WRRI Project No. 11-06-W
Karen Olmstead, Environmental Scientist; California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814; Tel. (916) 403-6879; email@example.com
Dean G. Kelch, Primary Botanist; California Department of Food and Agriculture; 1220 N Street, Sacramento, CA 95814; Tel. (916) 403-6650; firstname.lastname@example.org
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Pest Rating: D | Proposed Seed Rating: None
Posted by ls