United States 

Department of 

Agriculture 

Animal and 

Plant Health 

Inspection 

Service 

March 10, 2015 

Version 2 

Weed Risk Assessment for Thlaspi 

arvense L. (Brassicaceae) – Field 

pennycress

Left: Thlaspi arvense plant (source: Utah State University Archive, Utah State University, 

Bugwood.org). Top center: Senesced fruits (seed pods) (source: Ohio State Weed Lab Archive, 

The Ohio State University, Bugwood.org). Bottom center: Plants with seed pods growing in a 

field of winter wheat (source: Howard F. Schwartz, Colorado State University, Bugwood.org). 

Right: Fruit [source: Mary Ellen (Mel) Harte, Bugwood.org]. 

Agency Contact: 

Plant Epidemiology and Risk Analysis Laboratory 

Center for Plant Health Science and Technology 

Plant Protection and Quarantine 

Animal and Plant Health Inspection Service 

United States Department of Agriculture 

1730 Varsity Drive, Suite 300 

Raleigh, NC 27606 
Weed Risk Assessment for Thlaspi arvense

Ver. 2 March 10, 2015 1

Introduction Plant Protection and Quarantine (PPQ) regulates noxious weeds under the 

authority of the Plant Protection Act (7 U.S.C. § 7701-7786, 2000) and the 

Federal Seed Act (7 U.S.C. § 1581-1610, 1939). A noxious weed is defined 

as “any plant or plant product that can directly or indirectly injure or cause 

damage to crops (including nursery stock or plant products), livestock, 

poultry, or other interests of agriculture, irrigation, navigation, the natural 

resources of the United States, the public health, or the environment” (7 

U.S.C. § 7701-7786, 2000). We use weed risk assessment (WRA)—

specifically, the PPQ WRA model (Koop et al., 2012)—to evaluate the risk 

potential of plants, including those newly detected in the United States, 

those proposed for import, and those emerging as weeds elsewhere in the 

world. 

Because the PPQ WRA model is geographically and climatically neutral, it 

can be used to evaluate the baseline invasive/weed potential of any plant 

species for the entire United States or for any area within it. As part of this 

analysis, we use a stochastic simulation to evaluate how much the 

uncertainty associated with the analysis affects the model outcomes. We also 

use GIS overlays to evaluate those areas of the United States that may be 

suitable for the establishment of the plant. For more information on the PPQ 

WRA process, please refer to the document, Background information on the 

PPQ Weed Risk Assessment, which is available upon request. 

Thlaspi arvense L. – Field pennycress 

Species Family: Brassicaceae 

Information Synonyms: Crucifera thlaspi (Roxb.) E.H.L.Krause, Lepidium thlaspi

Roxb., Teruncius arvense (L.) Lunell, T. arvensis (L.) Lunell, Thlaspi 

baicalense DC., T. collinum Bieb. M, T. strictum Dalla Torre & Sarnth., 

Thlaspidea arvensis (L.) Opiz, Thlaspidium arvense (L.) Bubani (The 

Plant List, 2013; Tropicos.org, 2014). 

Common names: Field pennycress (CABI, 2014; NRCS, 2014); bastard 

cress, fanweed, Frenchweed, Mithridate mustard, pennycress, stinkweed, 

wild garlic (NGRP, 2014b). Preferred common name is field pennycress 

(CABI, 2014). 

Botanical description: Thlaspi arvense is an erect, annual herb (Holm et al., 

1997; NRCS, 2014). It starts out as a rosette of leaves, but then becomes 

an erect flowering stem (Uva et al., 1997), growing 18 to 80 cm tall 

(Holm et al., 1997). It produces small white flowers in terminal clusters; 

the fruit are flat, heart-shaped pods 1 to 2 cm long, each containing 4 to 

16 seeds (Royer and Dickinson, 1999). For a full botanical description, 

see eFloras (2014). 

Initiation: On August 4, 2014, the Environmental Protection Agency (EPA) 

contacted Jonathan Jones, USDA Biofuel Team Leader, with questions 

about the weed status of T. arvense (Lie, 2014). We later learned that the 

EPA wanted to know whether or not this species should be regulated 
Weed Risk Assessment for Thlaspi arvense

Ver. 2 March 10, 2015 2

under their Renewable Fuel Standard as a potential invasive species (Lie, 

2014). On October 6, the PPQ Weeds Cross-Functional Working Group 

requested that the PERAL Weed Team conduct a WRA of this species. 

Foreign distribution: Thlaspi arvense is native to and widespread in Europe 

and Asia (mainly temperate areas) and has naturalized in North America 

(Canada and the United States), Australia, and New Zealand, as well as 

parts of Africa (Algeria, Morocco, the Azores, the Madeira Islands, South 

Africa, the Canary Islands, Tunisia) and South America (Argentina, 

Brazil, Chile) (GBIF, 2014; Holm et al., 1991; NGRP, 2014b). It was 

recently introduced to Mexico (Vibrans, 2003), but we do not know if 

they consider it to be established there. 

 U.S. distribution and status: Thlaspi arvense was first detected in the United 

States (in Detroit, Michigan) in 1701 (Royer and Dickinson, 1999). Since 

then it has become naturalized in every state in the continental United 

States (Kartesz, 2013; NRCS, 2014). It is listed as one of the "most 

widespread invasive plants in North America" (NAISN, 2013). Although 

we found no evidence that this species is sold commercially in the United 

States, it may be cultivated privately to some extent [i.e., a person in 

Washington stated that they have seeds of the plant available for private 

trade on a gardening forum (Dave's Garden, 2014)]. Also, it is being 

proposed and developed as a potential oilseed biofuel plant here (ATI, 

2010; Dorn et al., 2013; Moser et al., 2009). Several states list it as a 

noxious weed in seed (Indiana, Kansas, Michigan, Minnesota, Nebraska, 

Nevada, Ohio, South Dakota, Washington) (NGRP, 2014a; AMS, 2014), 

and it is listed in the Invasive Plant Atlas of the United States 

(Swearingen, 2014). 

 WRA area1

: Entire United States, including territories. 

 

 1. Thlaspi arvense analysis 

Establishment/Spread 

Potential 

Beyond its native range in Eurasia, T. arvense has established widely 

throughout the world, including North America, Australasia, and parts of 

Africa and South America (GBIF, 2014; Holm et al., 1991; NGRP, 2014b; 

Salisbury, 1961). It was first detected in North America in 1701 (Royer and 

Dickinson, 1999) and became established throughout Canada and the United 

States by the 1930s (Best and McIntyre, 1975; Clark, 1923). It is an erect 

herb that is self-compatible (Best and McIntyre, 1975), has prolific seed 

production (Holm et al., 1997; Salisbury, 1961), forms a persistent seed 

bank (Bond et al., 2007; Warwick et al., 2002), and some populations have 

developed herbicide resistance (Heap et al., 2014; Warwick et al., 2002). 

Propagules can be dispersed as seed contaminants in trade (Holm et al., 

1997; NGRP, 2014b), via agricultural operations (e.g., combines) (Holm et 

 

1

 “WRA area” is the area in relation to which the weed risk assessment is conducted [definition modified from that for “PRA 

area”] (IPPC, 2012). 
Weed Risk Assessment for Thlaspi arvense

Ver. 2 March 10, 2015 3

al., 1997), by grazing animals that consume the seed (Pleasant and 

Schlather, 1994), by wind (Best and McIntyre, 1975; WSSA, 2014) and 

water (with spring floods) (Clark, 1923), and possibly by birds and 

externally on animals (Holm et al., 1997; Salisbury, 1961). We had low 

uncertainty for this risk element. 

Risk score = 22 Uncertainty index = 0.11 

Impact Potential Thlaspi arvense has likely been a weed of agriculture for several thousand 

years (Holm et al., 1997). Today it is a weed of nursery, horticultural, and 

agricultural crops (Uva et al., 1997). It is an important weed in many crops 

and countries, especially barley, oats, rape, sunflowers, wheat, forage crops, 

and oilseed (Holm et al., 1997; Warwick et al., 2002). It can cause serious 

yield losses of field crops, such as wheat and safflower (Holm et al., 1997; 

Warwick et al., 2002). The plant is poisonous to livestock (Darbyshire, 

2003; Stubbendieck et al., 2003; Warwick et al., 2002), and consumption of 

its seeds or leaves by cattle causes their milk and flesh to develop an offflavor (Warwick et al., 2002). Seed contaminants can also lower the quality 

of wheat and canola (Warwick et al., 2002; WSSA, 2014). Because it is a 

quarantine or regulated pest for multiple countries or regions of countries 

(EPPO, 2013; Groves et al., 2005; NGRP, 2014a; Warwick et al., 2002) and 

can be dispersed as a contaminant, it could impact trade. It may be 

allelopathic to some extent (Holm et al., 1997) and can strongly compete 

with plants for water (Best and McIntyre, 1975). Although it has been listed 

as a weed of natural areas (Groves et al., 2005; Randall, 2007) and gardens 

and waste areas (Royer and Dickinson, 1999), we found no evidence of it 

causing impacts in anthropogenic (e.g., cities, suburbs, roadways) or natural 

systems. We had average uncertainty for this risk element. 

Risk score = 3.3 Uncertainty index = 0.14 

Geographic Potential Thlaspi arvense is already naturalized in every state in the continental 

United States and occurs in about 75 percent of the counties (Kartesz, 2013; 

NRCS, 2014). Based on county distribution, it is not very widespread in the 

southeastern United States (Kartesz, 2013; NRCS, 2014). Using three 

climatic variables, we estimate that nearly all of the United States is suitable 

for the establishment of T. arvense (Fig. 1). This predicted distribution is 

based on the species’ known distribution in the world and includes pointreferenced localities and areas of occurrence. The map for T. arvense

represents the joint distribution of Plant Hardiness Zones 1-10, areas with 0-

100+ inches of annual precipitation, and the following Köppen-Geiger 

climate classes: steppe, desert, Mediterranean, humid subtropical, marine 

west coast, humid continental warm summers, humid continental cool 

summers, subarctic, and tundra. 

The estimated area is likely conservative as it only uses three climatic 

variables. Other environmental variables, such as soil and habitat type, may 

further limit the areas in which this species is likely to establish. Habitats of 
Weed Risk Assessment for Thlaspi arvense

Ver. 2 March 10, 2015 4

this plant include cropland, fallow fields, weedy meadows, rangeland, 

roadsides and railroads, gardens, lawns, nursery plots, waste areas, stream 

banks, bluffs, thickets, slopes, floodplains, and woods (Cowbrough, 2014; 

eFloras, 2014; Hilty, 2014; Holm et al., 1997; Warwick et al., 2002). This 

plant prefers disturbed areas (Hilty, 2014; Holm et al., 1997) and grows well 

on moist soil (Nawrocki, 2010). 

Entry Potential We did not assess the entry potential of Thlaspi arvense because it is already 

present in the United States (Kartesz, 2013; NAISN, 2013; NRCS, 2014). 

Figure 1. Predicted distribution of Thlaspi arvense in the United States. 

Map insets for Alaska, Hawaii, and Puerto Rico are not to scale.

 2. Results 

Model Probabilities: P(Major Invader) = 95.4% 

 P(Minor Invader) = 4.4% 

 P(Non-Invader) = 0.1% 

Risk Result = High Risk 

Secondary Screening = Not Applicable

 
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Figure 2. Thlaspi arvense risk score (black box) relative to the risk scores of 

species used to develop and validate the PPQ WRA model(other symbols). 

See Appendix A for the complete assessment. 

Figure 3. Model simulation results (N=5,000) for uncertainty around the 

risk score for Thlaspi arvense. The blue “+” symbol represents the medians 

of the simulated outcomes. The smallest box contains 50 percent of the 

outcomes, the second 95 percent, and the largest 99 percent. 
Weed Risk Assessment for Thlaspi arvense

Ver. 2 March 10, 2015 6

 3. Discussion 

The result of the weed risk assessment for Thlaspi arvense is High Risk 

(Fig. 2) and is well supported by our uncertainty simulation (Fig. 3). This 

species tolerates a wide range of environmental conditions. It is an 

important agricultural weed for multiple crops (e.g., wheat, forage, oilseeds) 

(Bridges, 1992; Holm et al., 1997; Warwick et al., 2002), and it can harm 

livestock health and the quality of animal products (Darbyshire, 2003; 

Stubbendieck et al., 2003; Warwick et al., 2002). Thlaspi arvense is usually 

described as occurring predominantly in or restricted to disturbed habitats 

(NatureServe, 2014). While it can impact agricultural production systems, 

we found no evidence of harm in anthropogenic or natural systems. 

Other groups have also assessed the risk of this plant. A WRA by the U.S. 

Forest Service (2014), resulted in a High risk score (= 19, well above the 

threshold of 6). The U.S. Forest Service model is based on the Australian 

WRA model (Pheloung et al., 1999) and therefore is similar to our model. 

On the other hand, the University of Alaska Anchorage’s Alaska Natural 

Heritage Program, using the “Alaska non-native plant invasiveness ranking 

form,” rated T. arvense “weakly invasive” (ANHP, 2011; Nawrocki et al., 

2010). A NatureServe (2014) assessment rated its overall U.S. Invasive 

Species Impact Rank as Low/Insignificant because it is often restricted to 

disturbed areas, but that tool does not evaluate potential impacts to 

agricultural areas. 

Thlaspi arvense is being proposed as a winter biofuel crop (Lie, 2014), and 

may also have industrial (chemical) uses (e.g., Fan et al., 2013). 

Furthermore, it is being tested as a rotational/cover crop (Johnson et al., 

2015; Phippen and Phippen, 2012; Royo-Esnal et al., 2015). While the 

weediness of T. arvense is firmly established, it is unclear what effect these 

potentially beneficial uses may have on its prevalence or impacts in other 

crops. 

Although we found no evidence that T. arvense has been bred for any 

particular traits resulting in reduced weed potential, because of its promise 

as a biofuel plant, it is an "attractive target for rapid domestication," and 

within the past five years concerted efforts to domesticate this plant have 

begun (Sedbrook et al., 2014). Those authors proposed that knowledge about 

other brassicas and "the advent of affordable next generation sequencing... 

can bring about the rapid domestication and improvement of pennycress.” 

Traits (and possible genes to target) identified as needing domestication 

include reducing seed dormancy, eliminating glucosinolate in seeds, and 

reducing pod shatter (Sedbrook et al., 2014). Pod shatter can result in 

significant harvest loss; 10-15 percent of seeds may be lost during harvest 

(Sedbrook et al., 2014). Improving all three traits in breeding lines used for 

biofuel production would decrease the weed risk. 
Weed Risk Assessment for Thlaspi arvense

Ver. 2 March 10, 2015 7

In agricultural settings, despite control efforts, T. arvense can interfere with 

crop production (see above) and persist in crop fields (Hume, 1987, 1988). 

Also, multiple populations in Canada have developed resistance to ALS 

inhibitor herbicides (Heap et al., 2014; Warwick et al., 2002). Nevertheless, 

other authors indicate it can be easily controlled with herbicides such as 

glyphosate and glufosinate (Sedbrook et al., 2014). Tillage, grubbing, 

digging, or hand pulling before flowering, as well as the use of various 

herbicides, are said to give excellent control of T. arvense (DiTomaso and 

Kyser, 2013). In Spain, the weed’s near disappearance in some regional 

cereal fields probably resulted from changes in management practices, such 

as greater use of conservation tillage and spraying glyphosate before sowing 

(Cirujeda et al., 2011). Many complex factors (e.g., weather, timing, 

biotypes, crops, years) may contribute to its interference with crops and ease 

of control. It is unknown how its production on a large scale may contribute 

to this complexity; therefore, additional study and monitoring seems 

appropriate if it is to be grown as a crop. 

 

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sp.) manure and its importance as a weed source for cropland. Weed 

Technology 8(2):304-310. 

Randall, J. M. 2007. The introduced flora of Australia and its weed status. 

CRC for Australian Weed Management, Department of Agriculture 

and Food, Western Australia, Australia. 528 pp. 

Randall, R. P. 2012. A Global Compendium of Weeds, 2nd Edition. 

Department of Agriculture and Food, Western Australia. 1115 pp. 

Reynolds, S. C. P. 2002. A Catalogue of Alien Plants in Ireland. National 

Botanic Gardens, Glasnevin, Ireland. 315 pp. 

Royer, F., and R. Dickinson. 1999. Weeds of Canada and the northern 

United States: A guide for identification. University of Alberta Press, 

Edmonton, Canada. 434 pp. 

Royo-Esnal, A., J. Torra, J. Recasens, J. Necajeva, and R. W. Gesch. 2015. 
Weed Risk Assessment for Thlaspi arvense

Ver. 2 March 10, 2015 12

Emergence of field pennycress (Thlaspi arvense L.): Comparison of 

two accessions and modelling. Industrial Crops and Products 66:161-

169. 

Rydahl, P. 2014. Planteværn Online: Thlaspi arvense L. Aarhus University 

(AU), Institut for Agroecology. Last accessed November 17, 2014, 

http://www.ipmdss.dk/cp/graphics/Name.asp?Language=enla&TaskID=1&NameID=35. 

Salisbury, E. 1961. Weeds and aliens. Collins, London. 384 pp. 

Sedbrook, J. C., W. B. Phippen, and M. D. Marks. 2014. New approaches to 

facilitate rapid domestication of a wild plant to an oilseed crop: 

Example pennycress (Thlaspi arvense L.). Plant Science 227:122-

132. 

Stubbendieck, J., M. J. Coffin, and L. M. Landholt. 2003. Weeds of the 

Great Plains. Nebraska Department of Agriculture, Lincoln, NE, 

U.S.A. 605 pp. 

Swearingen, J. 2014. Invasive plant atlas of the United States. National Park 

Service. Last accessed November 15, 2014, 

http://www.invasiveplantatlas.org/index.html. 

The Plant List. 2013. The Plant List, a working list of all plant species, 

Version 1.1. Royal Botanic Gardens, Kew and Missouri Botanical 

Garden http://www.theplantlist.org/. (Archived at PERAL). 

Tropicos.org. 2014. Thlaspi arvense L. Missouri Botanical Garden, Saint 

Louis, Missouri. Last accessed November 16, 2014, 

http://www.tropicos.org/Name/4100645?tab=synonyms. 

U.S. Forest Service. 2014. Pacific Island Ecosystems at Risk (PIER): Plant 

threats to Pacific ecosystems. United States Department of 

Agriculture, Forest Service. http://www.hear.org/pier/index.html. 

(Archived at PERAL). 

Uva, R. H., J. C. Neal, and J. M. DiTomaso. 1997. Weeds of the Northeast. 

Comstock Publishing (Cornell University Press), Ithaca, NY., U.S.A. 

398 pp. 

Vaughn, S. F., T. A. Isbell, D. Weisleder, and M. A. Berhow. 2005. 

Biofumigant compounds released by field pennycress (Thlaspi 

arvense) seedmeal. Journal of Chemical Ecology 31(1):167-177. 

Vibrans, H. 2003. Notes on neophytes 3. Distribution of some Brassicaceae 

recently introduced in central Mexico [Abstract]. Acta Botanica 

Mexicana (65):31-44. 

Warwick, S. I., A. Francis, and D. J. Susko. 2002. The biology of Canadian 

weeds. 9. Thlaspi arvense L. (updated). Canadian Journal of Plant 

Science 82(4):803-823. 

Westmoreland, G. 1983. Weeds of Alberta. Alberta Envrironmental Centre, 

Canada. 209 pp. 

WSSA. 2014. Field Pennycress - The Stinkweed. Weed Science Society of 

America (WSSA). Last accessed November 16, 2014, 

http://wssa.net/wpcontent/themes/WSSA/WorldOfWeeds/pennycress.html. 
Weed Risk Assessment for Thlaspi arvense

Ver. 2 March 10, 2015 13

Appendix A. Weed risk assessment for Thlaspi arvense L. (Brassicaceae). The following information came from 

the original risk assessment, which is available upon request (full responses and all guidance). We modified the 

information to fit on the page.

Question ID Answer - 

Uncertainty 

Score Notes (and references) 

ESTABLISHMENT/SPREAD POTENTIAL 

ES-1 

(Status/invasiveness 

outside its native range) 

f - negl 5 Thlaspi arvense is native to and widespread in Europe and Asia 

(mainly temperate areas) and has naturalized in North America 

(Canada and the United States), Australia, New Zealand, as well as 

parts of Africa (Algeria, Morocco, the Azores, the Madeira Islands, 

South Africa, the Canary Islands, Tunisia), and South America 

(Argentina, Brazil, Chile) (GBIF, 2014; Holm et al., 1991; NGRP, 

2014b; Salisbury, 1961). Also, it was recently introduced to Mexico 

(Vibrans, 2003), but it is unclear if it is considered established there 

or not. It has "widely spread" in temperate regions of the northern 

hemisphere (Warwick et al., 2002). Randall (2012), citing numerous 

sources, lists it as a species escaping cultivation and naturalizing. It 

was first detected in the United States (in Detroit, Michigan) in 1701 

(Royer and Dickinson, 1999), and by 1937 it "was distributed 

throughout the United States from Maine to Florida and westward to 

California and Washington" (Best and McIntyre, 1975). It was first 

detected in Canada in 1860 (Claudi et al., 2002) and then was found 

in every Canadian province by 1923 (Clark, 1923). In 1940 in 

Kansas, it was described as one of the weeds "spreading from the 

north to the south" in the state (Gates, 1940). In the United States, it 

is "common" ("those species that are widely existing, or prevalent") 

in crops in multiple states (Bridges, 1992). It is now naturalized in 

every state in the continental United States (Kartesz, 2013; NRCS, 

2014) and is one of the "most widespread invasive plants in North 

America" (NAISN, 2013). Alternate answers for the Monte Carlo 

simulation were both "e." 

ES-2 (Is the species 

highly domesticated) 

n - low 0 While it has been cultivated in various parts of the world for 

consumption of its leaves (WSSA, 2014) and is being developed as a 

potential oilseed biofuel plant (ATI, 2010; Dorn et al., 2013; Moser 

et al., 2009), we found no evidence that it has been bred for any 

particular traits resulting in reduced weed potential. Other risk 

assessors have also found no evidence of domestication that reduces 

invasive traits (U.S. Forest Service, 2014). "There has been little 

agronomic improvement in pennycress through traditional breeding" 

(Dorn et al., 2013). However, because of its promise as a biofuel 

plant, this plant is considered an "attractive target for rapid 

domestication," and traits (and possible genes to target) that have 

been identified as needing domestication include reducing seed 

dormancy, abolishing seed glucosinolate content, and reducing pod 

shatter (Sedbrook et al., 2014). We answered no with low 

uncertainty, because even if domestication has occurred (or will soon 

occur), it would be highly unlikely to affect the species as a whole. 

ES-3 (Weedy congeners) y - high 1 The genus Thlaspi contains six species (eFloras, 2014; Mabberley, 

2008). Randall (2012) lists species in the genus as agricultural weeds 

(e.g., T. alliaceum, T. perfoliatum), invasive plants (T. caerulescens, 

T. perfoliatum), quarantine weeds (T. cepaeifolium, T. 

microphyllum), and an environmental weed (T. perfoliatum) 

somewhere in the world. In Norway, after escaping cultivation in a 

botanical garden, T. caerulescens rapidly expanded its range and is 
Weed Risk Assessment for Thlaspi arvense

Ver. 2 March 10, 2015 14

Question ID Answer - 

Uncertainty 

Score Notes (and references) 

now present in all provinces and is frequent to common in many 

areas; however, it is noted as not being aggressive or representing a 

danger to native populations (Elven and Fremstad, 1996). We found 

no other evidence to indicate that congeners are causing significant 

direct or indirect impacts. Based on the use of only one reference 

(i.e., Randall, 2012), we use high uncertainty. 

ES-4 (Shade tolerant at 

some stage of its life 

cycle) 

n - negl 0 In a study in Sweden, it could not develop under conditions of low 

light (Holm et al., 1997). It requires "full sun" (Hansen, 2014). It 

"cannot grow in the shade" (PFAF, 2014). It is "shade intolerant" 

(Nawrocki, 2010). 

ES-5 (Climbing or 

smothering growth form) 

n - low 0 The plant is not a vine. It is an erect, annual herb (Holm et al., 1997; 

NRCS, 2014). It starts out as a rosette of leaves, but the basal leaves 

do not persist at maturity, and it then becomes an erect flowering 

stem (Uva et al., 1997), growing 18 to 80 cm tall (Best and McIntyre, 

1975; Holm et al., 1997). Although it can form basal rosettes, we 

found no evidence in the literature of them being described as flat 

and tightly appressed with overlapping leaves or as covering or 

smothering other plants. 

ES-6 (Forms dense 

thickets) 

? - max 0 Unknown. One author states that it "does not form dense thickets" 

(Nawrocki et al., 2010). However, according to Best and McIntyre 

(1975), this species "may grow as isolated plants, in small patches or 

in pure stands." Also, in Ireland, it sometimes occurs in "dense stands 

where obviously self-sown" (Reynolds, 2002). A website about its 

weed importance in Denmark states that a "dense population" may 

lead to yield loss in crops (Rydahl, 2014). We found no other 

evidence of this plant forming dense populations. We answered 

unknown, as we found conflicting evidence, and the evidence for 

dense populations is not very strong considering the fact that it is a 

very common weed. 

ES-7 (Aquatic) n - negl 0 Not an aquatic plant; this plant is a terrestrial herb (eFloras, 2014; 

Holm et al., 1997; NRCS, 2014; O’Flynn et al., 2014). 

ES-8 (Grass) n - negl 0 This plant is not in the family Poaceae (NGRP, 2014b). 

ES-9 (Nitrogen-fixing 

woody plant) 

n - negl 0 We found no evidence that T. arvense fixes nitrogen. It is not a 

member of one of the plant families known to fix nitrogen (Martin 

and Dowd, 1990). Also, it is a non-woody plant (Hansen, 2014). 

ES-10 (Does it produce 

viable seeds or spores) 

y - negl 1 Reproduces solely by seed (CABI, 2014; Cowbrough, 2014; Hansen, 

2014; Holm et al., 1997). 

ES-11 (Self-compatible 

or apomictic) 

y - negl 1 The species is "self-compatible and readily autogamous" (Best and 

McIntyre, 1975). The flowers have both male and female organs, and 

the plant is self-fertile (PFAF, 2014). It produces high yields of 

viable seeds via self-pollination (Holm et al., 1997). This plant is 

mainly autogamous (Bond et al., 2007). 

ES-12 (Requires special 

pollinators) 

n - negl 0 Although mainly autogamous (see ES-11) and not requiring 

specialized pollinators, there is some cross-pollination by insects 

(Bond et al., 2007; Holm et al., 1997); outcrossing rates have been 

estimated to range between 3 to 20 percent (Warwick et al., 2002). 

Multiple genera and species of Lepidoptera, Hymenoptera, and 

Diptera are reported to be "occasional visitors" on this plant (Best 

and McIntyre, 1975; Warwick et al., 2002). 

ES-13 (Minimum 

generation time) 

b - high 1 Thlaspi arvense is an annual (Kartesz, 2013; NRCS, 2014; 

Stubbendieck et al., 2003). It can be a winter, spring, or summer 

annual (Sedbrook et al., 2014; Uva et al., 1997). In the United States, 

it may behave as either a summer or winter annual (Bond et al., 
Weed Risk Assessment for Thlaspi arvense

Ver. 2 March 10, 2015 15

Question ID Answer - 

Uncertainty 

Score Notes (and references) 

2007). The minimum generative time is one year (U.S. Forest 

Service, 2014). However, one author states that its short life cycle 

permits "several generations per year" (Holm et al., 1997). Alternate 

answers for the Monte Carlo simulation were both "a." 

ES-14 (Prolific 

reproduction) 

y - negl 1 Thlaspi arvense is a prolific seed producer (Holm et al., 1997). The 

reported estimates of the number of seeds per plant range from 900 

(Hanf, 1983) to 2,000 (Salisbury, 1961), 7,000 (Nawrocki, 2010), 

15,000 (Moser et al., 2009), 20,000 (Holm et al., 1997; Salisbury, 

1961), and up to 50,000 (AgroAtlas, 2014). In crop production in 

Canada, its density has been reported to range from 52 to 137 plants 

per meter square (Warwick et al., 2002). Outside of cultivation, even 

if two to three plants occurred per square meter and with germination 

rates of 87 to 99 percent (Best and McIntyre, 1975), it readily meets 

our threshold of 5,000 viable seeds per square meter for a yes 

response. 

ES-15 (Propagules likely 

to be dispersed 

unintentionally by 

people) 

y - negl 1 Its spread is commonly associated with agricultural operations 

(Nawrocki et al., 2010). Dispersed locally by grain combines and 

other machinery, by mud on people's shoes, and by falling from 

vehicles during transport on farm roads (Holm et al., 1997). It is 

ranked among weeds that have the greatest seed fall during harvest 

operations (Holm et al., 1997). 

ES-16 (Propagules likely 

to disperse in trade as 

contaminants or 

hitchhikers) 

y - negl 2 It is a potential seed contaminant (CABI, 2014; Nawrocki, 2010; 

NGRP, 2014b). It spreads as a seed contaminant in cereal and flax 

seed stocks, and in India it is one of the common weed seeds found in 

wheat for sale (Holm et al., 1997). In Ireland, it was probably 

reintroduced with grain or animal seed; it has been found there in 

birdseed and in assemblages of exotic plants introduced with animal 

feed (Reynolds, 2002). The seeds can ripen before harvest, shatter, 

and subsequently infest crop seeds (AgroAtlas, 2014). In St. Louis, 

Missouri, it frequently forms colonies of different sizes on the 

margins of railroads as well as on the tracks (Mühlenbach, 1979). 

ES-17 (Number of 

natural dispersal vectors) 

5 4 Information relevant for ES-17a through ES-17e: The fruit (or seed 

pods) are flattened and oval to heart-shaped (Nawrocki, 2010) with a 

broad flat wing (Cowbrough, 2014), measuring 1-2 cm long and 7-20 

mm wide (Nawrocki, 2010). The seed-containing section is split into 

two compartments by a narrow membranous partition, each side 

containing 3 to 8 seeds; this membranous partition often remains on 

the plant after the pod breaks apart to release the seeds (Cowbrough, 

2014). The seeds are flattened, ovoid, 1-2 mm in length, 

approximately two-thirds the length in width, reddish-brown to 

purplish or blackish, and with several rows of concentric ridges on 

each side (Cowbrough, 2014; Salisbury, 1961). 

 ES-17a (Wind 

dispersal) 

y - mod Based on the available evidence, it is unclear to what extent wind 

contributes to seed dispersal, in particular to long distance spread. 

Some authors report that the seeds are disseminated via the wind 

(e.g., Kaul, 1986). The seedpods become detached from the plant and 

“blow about in the wind” (Hilty, 2014). Whereas some authors 

indicate that dispersal is mainly by wind (Best and McIntyre, 1975; 

WSSA, 2014), others suggest that wind disperses the seed only 

moderate distances (e.g., 1 km) (CABI, 2014; NatureServe, 2014). 

"Wind occasionally disperses seeds over long distances"; "[t]he wide 

distribution of field pennycress appears to result more from it being a 

contaminant in crop seed than from dispersal by wind" (Nawrocki, 
Weed Risk Assessment for Thlaspi arvense

Ver. 2 March 10, 2015 16

Question ID Answer - 

Uncertainty 

Score Notes (and references) 

2010). Its seed pods have broad wings (Cowbrough, 2014; eFloras, 

2014), which may assist with wind dispersal, and there are multiple 

references to its seed being dispersed by wind (e.g., Hilty, 2014; 

Kaul, 1986; Best and McIntyre, 1975; WSSA, 2014). However, 

Cowbrough (2014) states that the membranous partition of the pod 

often remains on the plant, suggesting that the seeds may often not be 

dispersed by wind. Given the number of references indicating that 

wind dispersal is involved, we answered yes; however, we used 

moderate uncertainty. 

 ES-17b (Water 

dispersal) 

y - low Seeds disperse with water greater distances than that with wind 

(DiTomaso and Healy, 2007). Its seeds are distributed by spring 

floods (WSSA, 2014). In Canada in 1923, one author observed that it 

is difficult to control "on account of the distribution of its seeds by 

spring floods" (Clark, 1923). "The seed has a high specific gravity 

and in water it sinks upon agitation, but Hope (1927) in Alberta, 

Canada found significant amounts of the seed moving with the flow 

in mains and laterals of irrigation systems" (cited in Holm et al., 

1997). One study found that ninety percent of seeds floated on still 

water for 24 hours (cited in Best and McIntyre, 1975). 

 ES-17c (Bird dispersal) y - mod It can disperse locally by "mud on the feet of...birds..." (Holm et al., 

1997). Viable seeds have been found in the excreta of pigeons and 

other birds (Salisbury, 1961). Seeds can be spread by sticking to 

feathers (cited in Nawrocki, 2010). Mourning doves will occasionally 

eat the seeds of weedy species in the mustard family (Hilty, 2014). 

Based on the evidence, it is unclear how often this type of dispersal 

may occur; therefore, we used moderate uncertainty. 

 ES-17d (Animal 

external dispersal) 

y - mod Can disperse locally by "mud on the feet of...animals" (Holm et al., 

1997). Over short distances the seed may be spread by being in the 

soil on the feet or fur of animals (CABI, 2014). 

 ES-17e (Animal 

internal dispersal) 

y - low Can disperse locally by animal dung as it is spread in fields (Holm et 

al., 1997). Seeds of it have been obtained from droppings of cattle 

and horses (Salisbury, 1961), and they can remain viable after 

passage through the digestive system of animals (Holm et al., 1997; 

AgroAtlas, 2014). In one study, up to 98 percent of seeds were able 

to germinate following rumen digestion (cited in Bond et al., 2007). 

On a dairy farm in New York, "apparently-viable" seeds of T. 

arvense were found in samples of cow manure, averaging 3,700 

seeds per 1,000 kg of manure (Pleasant and Schlather, 1994). On the 

other hand, because of its bitter-garlic flavor, T. arvense is not a 

preferred food source for mammalian herbivores (Hilty, 2014). 

ES-18 (Evidence that a 

persistent (>1yr) 

propagule bank (seed 

bank) is formed) 

y - negl 1 Thlaspi arvense has a persistent seed bank (Warwick et al., 2002). 

Most of the seed germinate within nine years (Nawrocki, 2010), but 

they can remain dormant up to 20 or more years (Nawrocki, 2010; 

Warwick et al., 2002; references cited in CABI, 2014). In a seed 

viability study, after three years of dormancy, 62 percent of the seeds 

were still viable, whereas after 30 years, 11 percent were still viable 

(Salisbury, 1961). After 10 years in the soil, seed can still have 87 

percent viability (Bond et al., 2007). 

ES-19 

(Tolerates/benefits from 

mutilation, cultivation or 

fire) 

n - low -1 We found no evidence that the plant tolerates or benefits from 

mutilation, cultivation, or fire, despite this being a common and 

widespread economically important agricultural weed. It does not 

resprout after removal of aboveground portions (Nawrocki et al., 

2010), and "[t]here is no evidence of vegetative reproduction" 
Weed Risk Assessment for Thlaspi arvense

Ver. 2 March 10, 2015 17

Question ID Answer - 

Uncertainty 

Score Notes (and references) 

(Warwick et al., 2002). Recommended measures for "excellent 

control" of this weed include tillage, digging, or hand pulling before 

flowering (DiTomaso and Kyser, 2013). 

ES-20 (Is resistant to 

some herbicides or has 

the potential to become 

resistant) 

y - negl 1 Thlaspi arvense is listed in Heap et al. (2014). "A resistant biotype to 

Group 2 herbicides, which inhibit acetolactate synthase (ALS), has 

been found at two to five sites in Alberta in 2001" (Warwick et al., 

2002). 

ES-21 (Number of cold 

hardiness zones suitable 

for its survival) 

10 1 

ES-22 (Number of 

climate types suitable for 

its survival) 

9 2 

ES-23 (Number of 

precipitation bands 

suitable for its survival) 

11 1 

IMPACT POTENTIAL 

General Impacts 

Imp-G1 (Allelopathic) y - high 0.1 In a study on allelopathic effects of seeds, some authors in Romania 

found that T. arvense seeds stimulated the germination and early 

growth of seeds of certain cultivated crops (e.g., rye, clover), but 

inhibited the germination of wheat seeds; these authors suggested 

that the active compounds are released in exudates from the newlyformed roots (Holm et al., 1997). Thlaspi arvense contains the 

glucosinolate sinigrin, which can be hydrolyzed to form compounds 

that may be involved in allelopathy (Vaughn et al., 2005). Defatted T. 

arvense seedmeal "completely inhibited seedling 

germination/emergence" of wheat and arugula in a laboratory study, 

and significantly reduced the dry weight of bioassay plants in field 

studies (Vaughn et al., 2005). Holm et al. (1997) is not an original 

source reference, and we were unable to verify the source they cited, 

and the Vaughn et al. (2005) report was of processed seedmeal, not 

of naturally occurring plants or seeds. Also, given this species is 

extremely common as an agricultural weed, we would expect there 

would be more reports if the species were strongly allelopathic. 

Given these factors, we answered yes but with high uncertainty. 

Imp-G2 (Parasitic) n - negl 0 We found no evidence this species is parasitic. Furthermore, Thlaspi 

arvense does not belong to a family known to contain parasitic plants 

(Heide-Jorgensen, 2008; NGRP, 2014b; Nickrent, 2009). 

Impacts to Natural Systems 

Imp-N1 (Change 

ecosystem processes and 

parameters that affect 

other species) 

n - low 0 We found no evidence of this type of impact. "No evidence of 

negative impact to natural systems" (U.S. Forest Service, 2014). 

“Field pennycress is not likely to have ecological impacts in 

undisturbed areas”; it requires sparsely vegetated soil in disturbed 

areas or cultivated lands in order to germinate (Nawrocki, 2010). It is 

widely described as occurring predominantly in or restricted to 

disturbed habitats (NatureServe, 2014). For instance, in Finland, it is 

not found growing in the wild (NatureGate, 2014), and in Ireland it is 

considered established mainly in artificial habitats (e.g., roadsides, 

disturbed ground, landfill sites, cultivated and formerly cultivated 

ground) (Reynolds, 2002). NatureServe (2014) ranked its ecological 

impact as "low/insignificant", and its overall U.S. Invasive Species 

Impact Rank (I-Rank) as Low/Insignificant based on it being 
Weed Risk Assessment for Thlaspi arvense

Ver. 2 March 10, 2015 18

Question ID Answer - 

Uncertainty 

Score Notes (and references) 

predominantly found in or restricted to disturbed areas. Although 

listed as a weed of natural areas by a few sources (see Imp-N6), these 

sources provide no information on the types or extent of impacts in 

natural areas. Based on this evidence (plus additional evidence below 

in this subelement) and because we found no evidence of impacts in 

natural areas, we used low uncertainty for this question and the others 

in this subelement. 

Imp-N2 (Change 

community structure) 

n - low 0 We found no evidence of this type of impact. 

Imp-N3 (Change 

community composition) 

n - low 0 We found no evidence of this type of impact. In Canada's Riding 

Mountain National Park, T. arvense was found only in ruderal (i.e., 

waste ground) habitats (not natural habitats), was considered to have 

a low risk of proliferation, and in the absence of soil disturbance was 

considered to "not threaten native biodiversity" (Otfinowski et al., 

2007). It is a poor competitor with grass species such as Agropyron 

cristatum, A. trachycaulum, and Bromus inermis (Best and McIntyre, 

1975), and when it colonizes abandoned prairie environments, it 

appears to have insignificant effects on the normal pattern of 

succession (NatureServe, 2014). 

Imp-N4 (Is it likely to 

affect federal Threatened 

and Endangered species) 

n - low 0 We found no evidence. This plant occurs predominantly in or 

restricted to disturbed habitats, and we found no evidence of negative 

impacts in natural areas (see Imp-N1, N2, and N3). 

Imp-N5 (Is it likely to 

affect any globally 

outstanding ecoregions) 

n - low 0 We found no evidence. This plant occurs predominantly in or 

restricted to disturbed habitats, and we found no evidence of negative 

impacts in natural areas (see Imp-N1, N2, and N3). 

Imp-N6 (Weed status in 

natural systems) 

b - mod 0.2 Listed as "a weed of the natural environment" in Australia (Randall, 

2007) and “invasive in natural areas in the U.S." (Swearingen, 2014). 

In Australia, it is also listed as an "environmental weed" with a score 

of 2 for natural ecosystems (2 = "Naturalised and known to be a 

minor problem warranting control at 3 or fewer locations within a 

State or Territory") (Groves et al., 2005), but this reference does not 

give any more information on control efforts in natural systems, nor 

does it cite any sources that we could verify. It is a Declared Noxious 

Weed and is prohibited from sale in Western Australia, Australia 

(Groves et al., 2005); however, this source does not indicate if the 

plant is being regulated because of impacts in natural systems. 

Alternate answers for the Monte Carlo simulation were "a" and "c." 

Impact to Anthropogenic Systems (cities, suburbs, roadways) 

Imp-A1 (Impacts human 

property, processes, 

civilization, or safety) 

n - low 0 No evidence of this type of impact. 

Imp-A2 (Changes or 

limits recreational use of 

an area) 

n - high 0 It can have a "strong, fetid, onionlike odor" (Callihan et al., 2000). 

When bruised the leaves release an unpleasant odor, which is 

responsible for the common name stinkweed used in Canada 

(Salisbury, 1961). We found no direct evidence for this type of 

impact; however, because it can produce an unpleasant odor, we 

answered no with high uncertainty. 

Imp-A3 (Outcompetes, 

replaces, or otherwise 

affects desirable plants 

and vegetation) 

? - max We found no direct evidence for this impact. However, considering 

that this plant occurs in gardens (Lorenzi and Jeffery, 1987; Warwick 

et al., 2002) and is reported to be a serious weed of gardens (Royer 

and Dickinson, 1999), that control measures for this weed are 

indicated for "home gardens" (Lorenzi and Jeffery, 1987), and that 

this plant can have important impacts on crop plants (see Imp-P1), it 
Weed Risk Assessment for Thlaspi arvense

Ver. 2 March 10, 2015 19

Question ID Answer - 

Uncertainty 

Score Notes (and references) 

seems likely that T. arvense may have some negative impacts on 

desirable plants and vegetation in home gardens. 

Imp-A4 (Weed status in 

anthropogenic systems) 

c - high 0.4 It is a serious weed of gardens and waste areas (Royer and 

Dickinson, 1999). The use of 2,4-D, paraquat, or a soil sterilant are 

recommended control options for this weed occurring in fence rows, 

waste areas, and industrial sites (Lorenzi and Jeffery, 1987). Control 

measures for T. arvense are indicated for "home gardens" (Lorenzi 

and Jeffery, 1987). This evidence suggests that people may be 

controlling this weed in these environments. Based on the use of 

indirect evidence, we used high uncertainty. Alternate answers for 

the Monte Carlo simulation were both "b." 

Impact to Production Systems (agriculture, nurseries, forest plantations, orchards, etc.) 

Imp-P1 (Reduces 

crop/product yield) 

y - negl 0.4 It can cause serious yield losses of field crops, especially in Canadian 

prairies (Warwick et al., 2002). In Canada, studies have shown that a 

light infestation can reduce wheat yields by 35 percent and a heavy 

infestation by 50 percent (Holm et al., 1997). In 1986-1989 studies in 

Canada, in combination with other weeds, it reduced winter wheat 

yield by 18-32 percent and safflower yield by up to 73 percent 

(Warwick et al., 2002). In the United States, it causes crop losses and 

is listed as "troublesome" (which are "species which despite weed 

control efforts are inadequately controlled and interfere with crop 

production and/or yield, crop quality, or harvest efficiency) in oats, 

wheat, and rye (Bridges, 1992). 

Imp-P2 (Lowers 

commodity value) 

y - negl 0.2 Seeds contaminating livestock feed can cause the animals to reject 

the feed (Westmoreland, 1983). When cattle do consume the seeds or 

leaves, it causes their milk and meat to develop an off-flavor 

(Cowbrough, 2014; Hilty, 2014; Holm et al., 1997; Warwick et al., 

2002). Grain contaminated with T. arvense seed can lead to ruined 

wheat flour and very sharply reduced price of the grain (WSSA, 

2014). Contaminated canola can lead to lowered quality through 

increased erucic acid levels in the extracted oil and glucosinolate 

content in the meal (Warwick et al., 2002). 

Imp-P3 (Is it likely to 

impact trade) 

y - low 0.2 It is an A1 quarantine pest for Mexico (EPPO, 2013), a declared 

noxious-weed seed in multiple U.S. states (NGRP, 2014a), a 

"secondary noxious" plant in the Weed Seeds Order by Agriculture 

Canada (which limits the number of seeds permitted in commercial 

seed lots) (Warwick et al., 2002), and a Declared Noxious Weed 

prohibited from sale in Western Australia, Australia (Groves et al., 

2005). Based on this evidence, plus the fact that it can be dispersed in 

trade as a contaminant (see ES-16), we answered yes. 

Imp-P4 (Reduces the 

quality or availability of 

irrigation, or strongly 

competes with plants for 

water) 

y - mod 0.1 Thlaspi arvense has an extensive root system that surrounds those of 

nearby plants, thereby competing for the uptake of water (Holm et 

al., 1997). In the Prairie Provinces of Canada, "it competes with 

crops for limited moisture supply, causing significant reductions in 

yield" (Best and McIntyre, 1975). It "competes keenly with crops for 

moisture" (WSSA, 2014). 

Imp-P5 (Toxic to 

animals, including 

livestock/range animals 

and poultry) 

y - negl 0.1 It is poisonous to livestock (Darbyshire, 2003; Stubbendieck et al., 

2003). While the leaves are usually not toxic to animals, the seeds are 

rich in oil glucosides and when ground with feed can result in breakdown products that are toxic to livestock (Holm et al., 1997). When 

contaminating hay or other fodder, its seeds or leaves can be toxic to 

animals (Warwick et al., 2002). Acute poisoning in cattle can lead to 

abortion, colic, peeling skin, massive submucosal edema of the walls 
Weed Risk Assessment for Thlaspi arvense

Ver. 2 March 10, 2015 20

Question ID Answer - 

Uncertainty 

Score Notes (and references) 

of forestomachs, and death (Warwick et al., 2002). Livestock feeding 

on large amounts of ground seeds may develop “chronic enteritis, 

haemorrhagic diarrheoa, colic, abortion, nephritis and haematuria, 

apathy and paralysis of heart and respiration” (Best and McIntyre, 

1975). The "contamination of hay and forage grain feed and 

associated toxic effects...has remained a serious problem, particularly 

for farmers in western Canada" (Warwick et al., 2002). 

Imp-P6 (Weed status in 

production systems) 

c - negl 0.6 There is evidence it has been a weed of agriculture for several 

thousand years, and today is a problem in 30 crops in 45 countries 

(Holm et al., 1997). It is a weed of nursery crops, horticultural, and 

agricultural crops (Uva et al., 1997). A “serious weed” of barley, 

oats, rape, sunflowers, and wheat in Canada; of barley and wheat in 

Korea; and of pastures and winter wheat in the United States (Holm 

et al., 1997). A "principal weed" of other crops (e.g., asparagus, 

beets, beans, onions, peas, root crops, cereals, horticultural crops, 

lucerne, maize, potatoes, oil seed rape) (Holm et al., 1997). An 

"important weed” of grain, oilseed, and forage crops in Canada, 

especially in the prairies (Warwick et al., 2002). There have been 

"continuous control efforts" against this weed (Holm et al., 1997). 

Control measures used against and recommended for this weed 

include grubbing, digging, and hand pulling before flowering, as well 

as chemical control (e.g., 2,4-D, glyphosate) (Clark, 1923; DiTomaso 

and Kyser, 2013; Sedbrook et al., 2014; Warwick et al., 2002). 

Alternate answers for the Monte Carlo simulation were both "b." 

GEOGRAPHIC 

POTENTIAL 

 Unless otherwise indicated, the following evidence represents 

geographically referenced points obtained from the Global 

Biodiversity Information Facility (GBIF, 2014). 

Plant hardiness zones 

Geo-Z1 (Zone 1) y - low N/A Canada and the United States (AK). 

Geo-Z2 (Zone 2) y - negl N/A Canada and the United States (AK). 

Geo-Z3 (Zone 3) y - negl N/A Canada, Finland, and the United States (CO). A few points in India. 

Geo-Z4 (Zone 4) y - negl N/A Finland, India, Norway, and the United States (CO). 

Geo-Z5 (Zone 5) y - negl N/A Norway and Sweden. Also the United States (SD) (NRCS, 2014). 

Geo-Z6 (Zone 6) y - negl N/A Norway and Sweden. Also the United States (KS). 

Geo-Z7 (Zone 7) y - negl N/A Austria, Germany, Spain, and the United States (OR). 

Geo-Z8 (Zone 8) y - negl N/A Belgium, France, and Spain. Also the United States (NC) (NRCS, 

2014). 

Geo-Z9 (Zone 9) y - negl N/A Spain, the Netherlands, and the United Kingdom. Also the United 

States (FL) (NRCS, 2014). 

Geo-Z10 (Zone 10) y - low N/A The United Kingdom and the United States (AZ, CA). A few points 

in Pakistan. Also in the United States (FL) (NRCS, 2014). 

Geo-Z11 (Zone 11) n - high N/A There was one point in Honduras and one in Guatemala, but these are 

likely spurious or misidentifications. 

Geo-Z12 (Zone 12) n - high N/A We found no evidence that this species occurs in this zone. The two 

points from Zone 11 were near the edge of this zone. 

Geo-Z13 (Zone 13) n - high N/A We found no evidence that this species occurs in this zone. 

Köppen -Geiger 

climate classes 

 

Geo-C1 (Tropical 

rainforest) 

n - high N/A Reported to occur in the United States in West Palm Beach, Florida 

(NRCS, 2014), but this county includes both tropical rainforest and 

humid tropical. Because we found no other evidence it occurs in 

tropical rainforests we answered no. 
Weed Risk Assessment for Thlaspi arvense

Ver. 2 March 10, 2015 21

Question ID Answer - 

Uncertainty 

Score Notes (and references) 

Geo-C2 (Tropical 

savanna) 

n - high N/A One point in Honduras, but this is likely spurious or a 

misidentification. 

Geo-C3 (Steppe) y - negl N/A Afghanistan and Spain. It often occurs in forest-steppe zones 

(AgroAtlas, 2014). 

Geo-C4 (Desert) y - mod N/A A few points in Afghanistan. Thlaspi arvense occurs in semi-desert 

zones more rarely than some other zones (AgroAtlas, 2014). 

Geo-C5 (Mediterranean) y - low N/A Australia, Portugal, and Spain. 

Geo-C6 (Humid 

subtropical) 

y - negl N/A A few points in India, Nepal, and Pakistan. Also in the United States 

(FL, GA, NC) (NRCS, 2014). 

Geo-C7 (Marine west 

coast) 

y - negl N/A France, Germany, and the United Kingdom. 

Geo-C8 (Humid cont. 

warm sum.) 

y - negl N/A The United States (KS, MO). 

Geo-C9 (Humid cont. 

cool sum.) 

y - negl N/A Canada, China, Germany, Norway, and Sweden. 

Geo-C10 (Subarctic) y - negl N/A Canada, China, Finland, Norway, and Sweden. It has been found in 

arctic Norway and Svalbard, at approximately 78°N (Nawrocki et al., 

2010). 

Geo-C11 (Tundra) y - negl N/A Norway, and a few points in Austria, Iceland, and Switzerland. 

Geo-C12 (Icecap) n - low N/A We found no evidence. 

10-inch precipitation 

bands 

 

Geo-R1 (0-10 inches; 0-

25 cm) 

y - high N/A A few points in Afghanistan, and a few in the United States either 

inside this band or right on the edge. 

Geo-R2 (10-20 inches; 

25-51 cm) 

y - negl N/A Afghanistan, Spain, India, and the United States. 

Geo-R3 (20-30 inches; 

51-76 cm) 

y - negl N/A Germany, Spain, and Sweden. 

Geo-R4 (30-40 inches; 

76-102 cm) 

y - negl N/A Belgium, France, Germany, and the United Kingdom. 

Geo-R5 (40-50 inches; 

102-127 cm) 

y - negl N/A France, Ireland, and the United Kingdom. 

Geo-R6 (50-60 inches; 

127-152 cm) 

y - negl N/A Germany, Ireland, and the United Kingdom. 

Geo-R7 (60-70 inches; 

152-178 cm) 

y - negl N/A Ireland, Norway, and the United Kingdom. 

Geo-R8 (70-80 inches; 

178-203 cm) 

y - negl N/A Germany, Norway, and a few points in the United Kingdom. 

Geo-R9 (80-90 inches; 

203-229 cm) 

y - negl N/A Norway and two points in the United Kingdom. 

Geo-R10 (90-100 inches; 

229-254 cm) 

y - mod N/A Canada, Norway, and one point on the edge in the United Kingdom. 

Geo-R11 (100+ inches; 

254+ cm) 

y - high N/A A few points in Norway, two points in Canada, and one point in the 

United States. 

ENTRY POTENTIAL 

Ent-1 (Plant already 

here) 

y - negl 1 Thlaspi arvense was first detected in the United States (in Detroit, 

Michigan) in 1701 (Royer and Dickinson, 1999), and since that time 

it has become naturalized in every state in the continental United 

States (Kartesz, 2013; NRCS, 2014). It is listed as one of the "most 

widespread invasive plants in North America" (NAISN, 2013). 

Ent-2 (Plant proposed 

for entry, or entry is 

 - N/A 
Weed Risk Assessment for Thlaspi arvense

Ver. 2 March 10, 2015 22

Question ID Answer - 

Uncertainty 

Score Notes (and references) 

imminent ) 

Ent-3 (Human value & 

cultivation/trade status) 

 - N/A 

Ent-4 (Entry as a 

contaminant) 

 

 Ent-4a (Plant present in 

Canada, Mexico, Central 

America, the Caribbean 

or China ) 

 - N/A 

 Ent-4b (Contaminant of 

plant propagative 

material (except seeds)) 

 - N/A 

 Ent-4c (Contaminant of 

seeds for planting) 

 - N/A 

 Ent-4d (Contaminant of 

ballast water) 

 - N/A 

 Ent-4e (Contaminant of 

aquarium plants or other 

aquarium products) 

 - N/A 

 Ent-4f (Contaminant of 

landscape products) 

 - N/A 

 Ent-4g (Contaminant of 

containers, packing 

materials, trade goods, 

equipment or 

conveyances) 

 - N/A 

 Ent-4h (Contaminants 

of fruit, vegetables, or 

other products for 

consumption or 

processing) 

 - N/A 

 Ent-4i (Contaminant of 

some other pathway) 

 - N/A 

Ent-5 (Likely to enter 

through natural 

dispersal) 

 - N/A