U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2009–1130

Prepared in cooperation with the U.S. Fish and Wildlife Service

Evaluation of Restoration Methods to Minimize Canada 

Thistle (Cirsium arvense) Infestation
Cover. Minnesota restoration field. Photograph by Diane L. Larson, U.S. Geological Survey, taken July 19, 2006.
Evaluation of Restoration Methods to 

Minimize Canada Thistle (Cirsium arvense) 

Infestation

By Diane L. Larson

Prepared in cooperation with the U.S. Fish and Wildlife Service

Open-File Report 2009–1130

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

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U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Larson, D.L., Evaluation of restoration methods to minimize Canada thistle (Cirsium arvense) infestation: 

U.S. Geological Survey Open-File Report 2009–1130, 48 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Methods...........................................................................................................................................................1

Results and Discussion.................................................................................................................................2

Thistle Stem Counts..............................................................................................................................2

Thistle Cover..........................................................................................................................................5

Planted Species Cover.........................................................................................................................7

Species Richness................................................................................................................................10

Minnesota ...................................................................................................................................12

Iowa .........................................................................................................................................16

Synthesis.......................................................................................................................................................21

Minnesota Sites ..................................................................................................................................21

Iowa Sites.............................................................................................................................................21

Acknowledgments.......................................................................................................................................23

References....................................................................................................................................................23

....

Figures

1–18. Graphs showing:

1. Soil texture at study sites in Minnesota (A) and Iowa (B) ............................................2

2. Canada thistle stem counts at sites in Minnesota (A) and Iowa (B)...........................3

3. Canada thistle stem counts by site and method for Minnesota (A) 

and Iowa (B) sites................................................................................................................4

4. Canada thistle stem counts by method and seed mix diversity 

at the Iowa sites...................................................................................................................5

5. Thistle cover as a function of planting method and site in 

Minnesota (A) and Iowa (B)...............................................................................................6

6. Canada thistle cover as a function of planting method and seed 

mix diversity at Iowa sites..................................................................................................7

7. Cover of planted species as a function of planting method and 

site at Minnesota sites........................................................................................................8

8. Cover of planted species over time as a function of seed mix 

diversity at Minnesota sites...............................................................................................8

9. Cover of planted species over 3 years at Iowa sites.....................................................9

10. Cover of planted species as a function of planting method and 

seed mix diversity at Iowa sites ........................................................................................9

11. Richness of planted species as a function of site, planting method, 

and seed mix diversity at sites in Minnesota................................................................10

12. Planted species richness at Iowa sites.........................................................................11

13. Species-specific responses to planting methods within sites 

at Minnesota sites for species present in all three seed mixes ................................13
iv

Conversion Factors

Multiply By To obtain

Length

meter (m) 3.281 foot (ft) 

Mass

gram 0.03527 ounce, avoirdupois (oz)

Constituent concentrations in soil are given in micrograms per gram (μg/g).

Tables

1. Range of values for soil characteristics...................................................................................3

2. Proportion of plots at Minnesota sites in which a species was 

encountered as a function of diversity of the seed mix .......................................................12

3. Proportion of plots at Iowa sites in which a species was encountered 

as a function of diversity of the seed mix ...............................................................................16

4. Proportion of plots at Iowa sites in which a species was encountered 

as a function of planting method..............................................................................................16

5. Proportion of plots at Iowa sites in which a species was encountered 

as a function of site ....................................................................................................................17

6. Standardized total effects for the dormant broadcast, summer 

broadcast, and summer drill planting methods at Minnesota sites...................................23

Appendix 1. Analysis of variance (ANOVA) tables for statistical tests ...........................................26

Appendix 2. Species in the Minnesota seed mixes............................................................................46

Appendix 3. Species in the Iowa seed mixes ......................................................................................47

14. Species-specific responses to planting methods within sites at 

Minnesota sites for species present in the medium and high 

diversity seed mixes..........................................................................................................14

15. Species-specific responses to planting methods within sites at 

Minnesota sites for species present in the high diversity seed 

mix only................................................................................................................................15

16. Species-specific responses to site and seed mix diversity at Iowa sites ...............18

17. Species-specific responses to planting method and seed mix diversity 

at Iowa sites .......................................................................................................................19

18. Species-specific responses to planting method and site at Iowa 

study sites ...........................................................................................................................20

19–20. Diagrams showing:

19. Hypothesized model for effects of soil characteristics on Canada 

thistle cover........................................................................................................................21

20. Structural equation models for dormant broadcast (A), summer 

broadcast (B), and summer drill (C) planting methods at 

Minnesota sites..................................................................................................................22
Evaluation of Restoration Methods to Minimize Canada 

Thistle (Cirsium arvense) Infestation

By Diane L. Larson

Abstract

The National Wildlife Refuge System has an active 

habitat restoration program and annually seeds thousands 

of hectares with native plant species. The noxious weed, 

Canada thistle (Cirsium arvense), plagues these restorations. 

This study evaluates planting methodology and seed mixes 

with the goal of recommending optimal methods to reduce 

infestation of noxious weeds, especially Canada thistle, in 

new restorations. Three planting methods (dormant season 

broadcast, growing season [summer] broadcast, and growing 

season [summer] drill) were fully crossed with three levels 

of seed diversity (10, 20, and 34 species [plus a fourth level, 

58 species, on the three sites in Iowa]) in a completely 

randomized design replicated on nine sites in Minnesota and 

Iowa. The propagule bank of Canada thistle was evaluated at 

each site. Planting occurred in winter 2004 and spring-summer 

2005. Here I report on results through summer 2007. None 

of the planting methods or seed mix diversities consistently 

resulted in reduced abundance of Canada thistle. Soil texture 

had the strongest influence; sites with greater proportions of 

clay had greater frequency and cover of Canada thistle than 

did sandy sites. At the Minnesota study sites, the dormant 

broadcast planting method combined with the highest seed 

diversity resulted in both the greatest cover of planted species 

as well as the greatest richness of planted species. At the 

Iowa sites, planted species richness was slightly greater in the 

summer drill plots, but cover of planted species was greatest 

in the dormant broadcast plots. Richness of planted species 

at the Iowa sites was maximized in the high diversity plots, 

with the extra-high diversity seed mix resulting in significantly 

lower species richness. Individual species responded to planting methods idiosyncratically, which suggests that particular 

species could be favored by tailoring planting methods to that 

species.

Introduction

Restoration is a hallmark of the National Wildlife 

Refuge System (U.S. Fish and Wildlife Service, 1999, p. 12). 

Region 3 of the U.S. Fish and Wildlife Service harbors one of 

the largest tallgrass prairie restorations in the world at Neal 

Smith National Wildlife Refuge (NWR), located in Iowa. 

Efforts to preserve and restore such rare habitats are at the 

core of the Service’s mission to “...administer a national 

network of lands and waters for the conservation, management, and where appropriate, restoration of the fish, wildlife, 

and plant resources and their habitats within the United States 

for the benefit of present and future generations of Americans” 

(National Wildlife Refuge System Improvement Act of 1997).

This study was done by U.S. Geological Survey in cooperation with Region 3 of the U.S. Fish and Wildlife Service. 

It represents the efforts of personnel at Neal Smith NWR and 

at Litchfield, Morris, and Fergus Falls Wetland Management 

Districts (WMDs), Minnesota, to experimentally test the 

effects of three seeding methods and three (four in Iowa) seed 

diversity mixes on the success of restoration plantings. In this 

report, I describe changes in species richness and vegetative 

cover of the planted native species as well as cover and stem 

counts of Canada thistle from 2005 through 2007.

Methods

We combined three planting methods (dormant-season 

broadcast [hereafter referred to as “dormant broadcast”], 

growing-season broadcast [hereafter “summer broadcast”], 

and growing-season drill [hereafter “summer drill”]) with 

three (four in Iowa) seed diversities (10, 20, or 34 species, 

plus 58 at Neal Smith NWR in Iowa) in a completely randomized design on each of nine sites (two at each of the WMDs 

and three at Neal Smith NWR). Each treatment was replicated 

12 times at each site, for a total of 108 12- × 12-m “cells” 

planted at each site. Within each cell we delineated a permanently marked 6- × 2-m sample plot. Here we counted all 

thistle stems. On a 0.25- × 4-m subplot within the sample plot, 

we measured species richness and cover of all species present. 

These cover and richness measurements were completed by a 

contractor from the University of Minnesota in 2005 and 2006 

and by a contractor from Iowa State University in 2007, with 

help from station staff in each year.

Prior to seeding, seedbank samples were collected at 

a subset of cells at each site. These samples were analyzed 

for thistle propagules by contractors at the U.S. Department 
Figure 1. Soil texture at study sites in Minnesota (A) and Iowa (B). Shown are least square means and standard errors.

A Percent sand and clay by site, Minn. B Percent sand and clay by site, Iowa

SITE

DIEKMANN

FAHL

HEINOLA

KANDIYOHI

MEADOWS

MEEKER

TEXTURE, PERCENT

0

20

40

60

80

100

Sand

Clay

HARMISON

ORBWEAVER

PRODUCTION

Sand

Clay

SITE

TEXTURE, PERCENT

0

20

40

60

80

100

2 Evaluation of Restoration Methods to Minimize Canada Thistle (Cirsium arvense) Infestation

of Agriculture, Agricultural Research Service’s Morris field 

station. In addition, soil samples were collected for texture and 

nitrogen analyses; these samples were analyzed by contractors 

at the University of Minnesota.

Basic statistical analyses of the data were performed 

by using repeated measures analysis of variance (ANOVA) 

(SAS GLM, version 9.2) for the years 2005–07. Because 

Canada thistle abundance, as described below, was much 

greater on the Minnesota study sites than at the Neal Smith 

NWR sites in Iowa, Minnesota and Iowa sites were analyzed 

separately for all analyses. When high-order interaction terms 

made ANOVAs hard to interpret, structural equation models 

were used to evaluate differences in response variables (for 

example, cover of Canada thistle, cover of planted species) 

that might be attributed to multivariate, site-specific characteristics (for example, soil texture, nitrogen cycling).

Results and Discussion

Soil texture and propagule bank results were reported 

in the 2006 interim report and are summarized here. There 

was no spatial structure in soil texture within sites, but sites 

did differ from each other in the percentage of sand, silt, and 

clay in their soil (fig. 1). Meeker, at Litchfield WMD, was the 

sandiest site and also had the smallest percentage of clay. Sites 

Orbweaver and Production, at Neal Smith NWR, had the least 

sand and the highest percentage of silt. (Tables of results of all 

ANOVAs in this report are compiled in appendix 1.)

The range of values for soil characteristics at Minnesota 

and Iowa sites is presented in table 1. Results presented in this 

report can likely be generalized within these ranges but should 

not be used to extrapolate outside of them.

Thistle seed was detected on nine plots at site Heinola 

(Fergus Falls WMD), five plots at site Fahl (Morris WMD), 

and one plot each at sites Diekmann (Morris WMD), 

Meadows (Fergus Falls WMD), and Kandiyohi (Litchfield 

WMD). No thistle seeds were found at Meeker (Litchfield 

WMD) or at Production, Orbweaver, and Harmison (Neal 

Smith NWR). No root fragments from any site sprouted. The 

lack of a thistle propagule bank at most sites, combined with 

the obvious presence of Canada thistle in the vegetation, 

suggests either that windblown seeds are entering the sites 

or that our sampling intensity was insufficient to adequately 

characterize the thistle seedbank.

Thistle Stem Counts

Because of the vast difference in the amount of thistle 

at the Neal Smith NWR (Iowa) sites and the WMD (Minnesota) sites (fig. 2), as well as the landscape-level differences 

(for example, proximity to thistle infestations) between the 

NWR and the WMD sites, I have analyzed these two data sets 

separately by using repeated measures ANOVA for the years 

2005–07 in Minnesota and Iowa.

There was a significant interaction between site and 

planting method with respect to thistle stem counts at both 

the Minnesota and Iowa study sites (fig. 3). In Minnesota, 

the dormant broadcast method had more thistle stems at 

three sites, fewer at one site, and did not vary from the other 

planting methods at two sites. The increase between 2005 

and 2006 was much larger than between 2006 and 2007 at all 

Minnesota sites except Diekmann. In Iowa, only Production 

showed a substantial increase in thistle stems over time, and 

this increase was greatest in the dormant broadcast plots. In 
Table 1. Range of values for soil characteristics. 

[Values reported are means for study sites within the two States, with the range for individual plots in parentheses. %, percent; μg, microgram; g, gram]

Soil variable Minnesota sites (range) Iowa sites (range)

Sand (%) 53–82 (48–91) 43–56 (42–75)

Silt (%) 10–24 (2–29) 25–34 (13–38)

Clay (%) 7–24 (5–29) 19–23 (10–25)

Nitrogen mineralization rate (μg/g soil/day) 0.77–1.1 (0.470–2.113) 0.81–0.96 (0.379–1.627)

Net nitrification (μg/g soil/day) 1.6–2.8 (0.852–5.793) 1.3–1.7 (0.802–2.911) 

A Thistle stem counts by site, Minn.

SITE SITE

DIEKMANN

HEINOLA

KANDIYOHI

MEADOWS

MEEKER

COUNT OF STEMS, NUMBER

0

20

40

60

80

100

120

2005

2006

2007

FAHL

B Thistle stem counts by site, Iowa

HARMISON

ORBWEAVER

PRODUCTION

STEMS, NUMBER

0

1

2

3

4

5

6

7

2005

2006

2007

Figure 2. Canada thistle stem counts at sites in Minnesota (A) and Iowa (B). Note that the y-axis differs between the two graphs. 

Shown are least square means and standard errors.

Results and Discussion 3
Figure 3. Canada thistle stem counts by site and method for Minnesota (A) and Iowa (B) sites. For each site, the first three bars are 

2005 counts, the second three are 2006, and the third three are 2007. Note the different range of the y-axes in the two graphs. Shown are 

least square means and standard errors.

A Thistle stems by method and site, Minn. sites 2005−07

SITE

DIEKMANN FAHL HEINOLA KANDIYOHI MEADOWS MEEKER

COUNT OF STEMS, NUMBER

0

20

40

60

80

100

120

140

Dormant broadcast

Summer broadcast

Summer drill

B Thistle stems by method and site, Iowa sites 2005−07

SITE

HARMISON ORBWEAVER PRODUCTION

COUNT OF STEMS, NUMBER

0

2

4

6

8

10

12

14

Dormant broadcast

Summer broadcast

Summer drill

4 Evaluation of Restoration Methods to Minimize Canada Thistle (Cirsium arvense) Infestation
Figure 4. Canada thistle stem counts by method and seed mix diversity at the Iowa sites. For each 

year, the first four bars represent the dormant broadcast method, the second four represent the 

summer broadcast, and the third four represent the summer drill. Shown are least square means and 

standard errors.

YEAR

2005 2006 2007

COUNT OF STEMS, NUMBER

0

2

4

6

8

10

12

14

Extra-high

High

Medium

Low

Results and Discussion 5

addition, the Iowa sites had a significant method-by-diversity 

interaction (fig. 4). The low diversity plots had more thistle 

stems in 2007 than did the plots of other diversity levels.

Thistle Cover

 In the repeated measures analysis, there was a significant 

interaction between site and planting method over time at both 

the Minnesota and the Iowa sites (fig. 5). In Minnesota, thistle 

cover has continued to increase at Diekmann, Kandiyohi, and 

Meadows but has leveled off at the other three sites. Dormant 

broadcast plots tended to have more thistle than did the other 

two planting methods at Fahl and Kandiyohi but less at 

Diekmann. In Iowa, only Production has undergone a significant increase in thistle cover over the 3 years, and this increase 

has been primarily in the dormant broadcast plots, as was the 

case for thistle stem counts.

Thistle cover in Iowa was also influenced by diversity 

of the seed mix, and effect of the seed mix varied by planting 

method (fig. 6). The low diversity seed mix in the dormant 

broadcast method had the highest thistle cover at the Iowa 

sites in 2007. All other method-by-diversity combinations 

had similar amounts of thistle cover in 2007. Although thistle 

cover has increased over the 3 years of the study, it is still 

substantially lower in Iowa than in the Minnesota sites, with 

the exception of Heinola.
Figure 5. Thistle cover as a function of planting method and site in Minnesota (A) and Iowa (B). Within each site, the first three bars 

represent 2005 measurements, the second three represent 2006 measurements, and the third three represent 2007 measurements. Note 

that the y-axes differ on the two graphs. Shown are least square means and standard errors.

Dormant broadcast

Summer broadcast

Summer drill

A Thistle cover by method and site in Minnesota

COVER, PERCENT

0

20

40

60

80

SITE

DIEKMANN FAHL HEINOLA KANDIYOHI MEADOWS MEEKER

SITE

HARMISON ORBWEAVER PRODUCTION

COVER, PERCENT

0

2

4

6

8

10

12

14

Dormant broadcast

Summer broadcast

Summer drill

B Thistle cover by method and site in Iowa

6 Evaluation of Restoration Methods to Minimize Canada Thistle (Cirsium arvense) Infestation
Figure 6. Canada thistle cover as a function of planting method and seed mix diversity at Iowa sites. 

Within each year, the first three bars represent the dormant broadcast method, the second three 

represent the summer broadcast, and the third three represent the summer drill. Shown are least 

square means and standard errors.

YEAR

2005 2006 2007

COVER, PERCENT

0

2

4

6

8

10

12

14

Extra-high

High

Medium

Low

Results and Discussion 7

Planted Species Cover

In Minnesota, cover of planted species varied by method, 

and this variation differed depending on site (fig. 7). Cover of 

planted species increased over the 3 years of the study, with 

the dormant broadcast planting method showing the largest 

amount of cover in each year for each site except Diekmann, 

where the summer drill had a slight advantage over the other 

two planting methods. Cover of planted species in summer 

broadcast and summer drill plots was generally similar, except 

at Kandiyohi, where the summer broadcast lagged behind the 

summer drill. The difference between the effects of seed mix 

diversity levels on cover of planted species has been accentuated over time, with the high diversity seed mix having the 

greatest and the low diversity seed mix having the lowest 

cover of planted species in both 2006 and 2007 (fig. 8).

In Iowa, cover of planted species varied significantly 

by site (fig. 9); cover increased in each year, with Orbweaver 

having the highest cover of planted species in both 2006 and 

2007. There was a significant interaction between planting 

method and seed mix diversity (fig. 10) as well. The extrahigh seed diversity treatment had lower than expected cover 

of planted species. The dormant broadcast method generally 

produced greater cover of planted species than did the other 

two planting methods. Planted cover in the summer broadcast 

and summer drill methods was especially depressed in the 

extra-high diversity seed mix in 2006 and 2007.
Figure 7. Cover of planted species as a function of planting method and site at Minnesota sites. Within each site, the first three bars 

represent 2005 measurements, the second three 2006 measurements, and the third three 2007 measurements. Shown are least square 

means and standard errors.

Figure 8. Cover of planted species over time as a function of seed mix diversity at Minnesota sites. 

Shown are least square means and standard errors.

COVER, PERCENT

0

20

40

60

80

100

120

Dormant broadcast

Summer broadcast

Summer drill

SITE

DIEKMANN FAHL HEINOLA KANDIYOHI MEADOWS MEEKER

YEAR

2005 2006 2007

COVER, PERCENT

0

20

40

60

80

100

High

Medium

Low

8 Evaluation of Restoration Methods to Minimize Canada Thistle (Cirsium arvense) Infestation
Figure 9. Cover of planted species over 3 years at Iowa sites. Shown are least square means and 

standard errors.

Figure 10. Cover of planted species as a function of planting method and seed mix diversity at Iowa 

sites. Within each year, the first three bars refer to the extra-high diversity, the next three to the high 

diversity, the next three to the medium diversity, and the last three to the low diversity. Shown are least 

square means and standard errors.

SITE

HARMISON ORBWEAVER PRODUCTION

COVER, PERCENT

0

20

40

60

80

2005 

2006 

2007 

YEAR

2005 2006 2007

COVER, PERCENT

0

20

40

60

80

100

Dormant broadcast

Summer broadcast

Summer drill

Results and Discussion 9
Figure 11. Richness of planted species as a function of site, planting method, and seed mix diversity at sites in Minnesota. 

Within each site, the first three bars represent the dormant broadcast method, the second three represent the summer 

broadcast, and the third three represent the summer drill. Shown are least square means and standard errors. PLANTED SPECIES RICHNESS, NUMBER

0

5

10

15

20

25

SITE

DIEKMANN FAHL HEINOLA KANDIYOHI MEADOWS MEEKER

High

Medium

Low

10 Evaluation of Restoration Methods to Minimize Canada Thistle (Cirsium arvense) Infestation

Species Richness

Unlike in 2005 and 2006, when we only measured 

species richness in the subplots used to measure cover, in 2007 

we counted the number of species in the entire 2- × 6-m plot. 

Therefore, this ANOVA evaluated the effects of site, planting 

method, seed diversity, and their interactions in 2007 only. 

In Minnesota sites, richness of planted species varied in 

a complex three-way interaction among site, planting method, 

and seed diversity (fig. 11). In most cases, the high diversity 

seed mix resulted in greater species richness than did the 

medium and low diversity mixes; however, at Kandiyohi, 

Meadows, and Meeker, the high and medium diversity mixes 

did not differ when the summer broadcast planting method 

was used. At every site in Minnesota, the dormant broadcast 

planting method combined with the high diversity seed mix 

resulted in the greatest number of desired species.

Richness of planted species at the Iowa sites varied by 

site and seed mix diversity (fig. 12A) and by method and seed 

mix diversity (Figure 12B). The extra-high diversity seed mix 

resulted in lower species richness than did the high diversity 

mix in every case; only in the dormant broadcast planting 

method did more species become established from the extrahigh diversity mix than from the medium diversity mix. The 

low diversity seed mix had higher species richness in the 

summer drill planting method than in the other two methods; 

the medium diversity seed mix did not vary in species richness 

among the three planting methods.

The complete list of species in the seed mixes and their 

proportional representation in the plots can be found in appendix 2 (Minnesota) and appendix 3 (Iowa).
Figure 12. Planted species richness at Iowa sites. A, Richness as a function of site and seed mix 

diversity. B, Richness as a function of planting method and seed mix diversity. Shown are least square 

means and standard errors.

SITE

HARMISON ORBWEAVER PRODUCTION

PLANTED SPECIES RICHNESS, NUMBER

0

2

4

6

8

10

12

14

16

METHOD

SPECIES RICHNESS, NUMBER

0

2

4

6

8

10

12

14

16

Extra-high

High

Medium

Low

Extra-high

High

Medium

Low

A Planted species richness by site and seed mix diversity at Iowa sites

B Planted species richness by method and seed mix diversity at Iowa sites

DORMANT BROADCAST SUMMER BROADCAST SUMMER DRILL

Results and Discussion 11
Table 2. Proportion of plots at Minnesota sites in which a species was encountered as a function of diversity of the seed mix.

[Shown are least square means plus or minus (+) standard error. NA, species not present in the low diversity mix]

Species Diversity of seed mix

High Medium Low

Dalea purpurea 0.33+0.027 0.45+0.027 0.50+0.027

Aster novae-angliae 0.36+0.026 0.39+0.026 0.54+0.026

Heliopsis helianthoides 0.82+0.021 0.93+0.021 NA

Coreopsis palmata 0.54+0.027 0.63+0.027 NA

Dalea candida 0.35+0.026 0.43+0.026 NA

Lespediza capitata 0.39+0.026 0.28+0.026 NA

Potentilla arguta 0.19+0.024 0.31+0.024 NA

12 Evaluation of Restoration Methods to Minimize Canada Thistle (Cirsium arvense) Infestation

Minnesota

Only two species that were planted at Minnesota sites 

failed to appear by 2007: Carex bicknellii and Liatris aspera. 

Many species were less frequently encountered as the diversity of the seed mix increased (table 2), which is expected 

because the amount of seed was kept constant as more species 

were added. Lespedeza capitata was an exception to this trend. 

Among the grasses, Elymus canadensis and E. trachycaulus

appeared on virtually every plot on which they were planted; 

Andropogon gerardii and Bouteloua curtipendula also had 

high establishment. Sorghastrum nutans and Sporobolus 

asper, however, were encountered on only about a quarter of 

the plots where they were planted (appendix 2). Four of the 

five most prevalent forbs were in the Asteraceae; the fifth was 

a mint. Among the five least prevalent forbs were three asters, 

a rose, and a lily (appendix 2).

The most frequent pattern encountered for individual 

species in Minnesota was a site-by-method interaction 

(figs. 13, 14, and 15). In only one case, Ratibida columnifera

at Kandiyohi, was the summer broadcast clearly superior to 

the other two planting methods. Several species, including 

Aster novae-angliae, Sorghastrum nutans, Coreopsis palmata,

Panicum virgatum, Sporobolus asper, and Zizia aurea were 

generally favored by the dormant broadcast planting method. 

Dalea candida was mainly favored by the summer drill 

planting method. In many cases, both dormant broadcast and 

summer drill produced similar results. Three species, Verbena 

stricta, Artemisia ludoviciana, and Solidago rigida, had 

significant three-way interactions among site, diversity, and 

method, which rendered the result difficult to interpret.
Figure 13. Species-specific responses to planting methods within sites at Minnesota sites for species present in all three seed mixes. 

Proportion refers to the proportion of plots in which each species was encountered. Shown are least square means and standard 

errors.

Dormant broadcast

EXPLANATION

Summer broadcast

Summer drill

Andropogon gerardii

PROPORTION

0.0

0.2

0.4

0.6

0.8

1.0

1.2

PROPORTION

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Bouteloua curtipendula

Dalea purpurea Helianthus maximiliani

Aster novae-angliae Monarda fistulosa

Schizachyrium scoparium

DIEKMANN

FAHL

HEINOLA

KANDIYOHI

MEADOWS

MEEKER

0.0

0.2

0.4

0.6

0.8

1.0 Sorghastrum nutans

SITE SITE

PROPORTION

DIEKMANN

HEINOLA

KANDIYOHI

MEADOWS

MEEKER

PROPORTION

0.0

0.2

0.4

0.6

0.8

1.0

1.2

FAHL

Results and Discussion 13
Figure 14. Species-specific responses to planting methods within sites at Minnesota sites for species present in the medium and 

high diversity seed mixes. Proportion refers to the proportion of plots in which each species was encountered. Shown are least square 

means and standard errors.

DIEKMANN

FAHL

HEINOLA

KANDIYOHI

MEADOWS

MEEKER

PROPORTION

0.0

0.2

0.4

0.6

0.8

1.0

1.2

PROPORTION

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Dormant broadcast

EXPLANATION

Summer broadcast

Summer drill

PROPORTION

0.0

0.2

0.4

0.6

0.8

1.0

1.2

PROPORTION

0.0

0.2

0.4

0.6

0.8

1.0

1.2

DIEKMANN

FAHL

HEINOLA

KANDIYOHI

MEADOWS

MEEKER

SITE

SITE

Coreopsis palmata

Lespedeza capitata Panicum virgatum

Potentilla arguta

Dalea candida

Sporobolus asper

Zizia aurea

14 Evaluation of Restoration Methods to Minimize Canada Thistle (Cirsium arvense) Infestation
Figure 15. Species-specific responses to planting methods within sites at Minnesota sites for species present in the high diversity 

seed mix only. Proportion refers to the proportion of plots in which each species was encountered. Shown are least square means and 

standard errors.

DIEKMANN

FAHL

HEINOLA

KANDIYOHI

MEADOWS

MEEKER

PROPORTION

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Dormant broadcast

EXPLANATION

Summer broadcast

Summer drill

PROPORTION

0.0

0.2

0.4

0.6

0.8

1.0

1.2

PROPORTION

0.0

0.2

0.4

0.6

0.8

1.0

1.2

DIEKMANN

FAHL

HEINOLA

KANDIYOHI

MEADOWS

MEEKER

SITE

SITE

Desmodium canadense

Ratibida columnifera Rudbeckia hirta

Stipa viridula

Elymus trachycaulus

Results and Discussion 15
16 Evaluation of Restoration Methods to Minimize Canada Thistle (Cirsium arvense) Infestation

Iowa

Seven species that were planted at Iowa sites were not 

encountered in our 2007 surveys: Phlox pilosa, Amorpha 

canescens, Aster azureus, Coreopsis tripteris, Gentiana 

flavida, Sporobolus heterolepis, and Tradescantia bracteata. 

Of these, P. pilosa was in the high and extra-high diversity 

seed mix, and the rest were in only the extra-high diversity 

mix (appendix 3). Surprisingly, several species that were 

in all four of the seed mixes were rarely encountered in the 

survey. These included Verbena stricta, Helianthus occidentalis, and Aster novae-angliae. As in Minnesota, some species 

had a significant relation to seed mix diversity, and most of 

those had greater frequencies in the lower diversity plots, 

Table 3. Proportion of plots at Iowa sites in which a species was encountered as a function of diversity of the seed mix.

[Shown are least square means plus or minus (±) standard error. Of the species shown, only M. fistulosa was included in the low diversity mix; 

R. pinnata was not present in the medium diversity mix]

Species Diversity of seed mix

Extra-high High Medium Low

Monarda fistulosa 0.38±0.045 0.44±0.045 0.56±0.045 0.69+0.045

Dalea candida 0.14±0.041 0.37±0.041 0.32±0.041

Lespedeza capitata 0.26±0.042 0.65±0.042 0.64±0.042

Panicum virgatum 0.60±0.042 0.81±0.042 0.76±0.042

Sporobolus asper 0.37±0.044 0.53±0.044 0.43±0.044

Ratibida pinnata 0.33±0.042 0.77±0.042

again because of a higher proportion of seed of each species 

included in that mix (table 3). While there were always large 

declines in frequency between high and extra-high plots, there 

were many cases where there was little difference in frequency 

between high and medium diversity. Of the species that varied 

significantly by planting method as a main effect (table 4), 

some were strongly favored by either summer drill or dormant 

broadcast; none were favored by summer broadcast. Despite 

the overall similarity among the three sites (table 1, fig. 1), 

many species varied substantially in the proportion of plots 

occupied as a function of site (table 5).

Table 4. Proportion of plots at Iowa sites in which a species was encountered as a function of planting method.

[Shown are least square means plus or minus (±) standard error]

Species

Method

Dormant broadcast Summer broadcast Summer drill

Monarda fistulosa 0.43±0.039 0.47±0.039 0.65±0.039

Schizachyrium scoparium 0.24±0.037 0.32±0.037 0.46±0.037

Sorghastrum nutans 0.63±0.035 0.65±0.035 0.79±0.035

Panicum virgatum 0.68±0.042 0.67±0.042 0.82±0.042

Potentilla arguta 0.18±0.028 0.10±0.028 0.028±0.028

Sporobolus asper 0.69±0.044 0.32±0.044 0.31±0.044

Tradescantia ohiensis 0.24±0.050 0.18±0.050 0.42±0.050

Asclepias tuberose 0.67±0.073 0.22±0.073 0.31±0.073

Desmodium canadense 0.17±0.075 0.42±0.075 0.56±0.075
Results and Discussion 17

Table 5. Proportion of plots at Iowa sites in which a species was encountered as a function of site.

[Shown are least square means plus or minus (±) standard error]

Species

Site

Harmison Orbweaver Production

Monarda fistulosa 0.44±0.039 0.49±0.039 0.63±0.039

Dalea candida 0.37±0.041 0.15±0.041 0.32±0.041

Heliopsis helianthoides 0.55±0.039 0.70±0.039 0.80±0.039

Panicum virgatum 0.63±0.042 0.78±0.042 0.75±0.042

Potentilla arguta 0.17±0.028 0.01±0.028 0.13±0.028

Sporobolus asper 0.41±0.044 0.56±0.044 0.36±0.044

Asclepias tuberosa 0.25±0.073 0.42±0.073 0.53±0.073

Delphinium virescens 0.14±0.066 0.11±0.066 0.44±0.066

Desmodium canadense 0.22±0.075 0.42±0.075 0.50±0.075

Thalictrum dasycarpum 0.22±0.070 0.11±0.070 0.61±0.070

Seven species had a significant interaction between 

site and seed mix diversity (fig. 16). In general, species that 

occurred only in the extra-high diversity mix were not as 

represented in the plots as were those in the high diversity 

seed mix. Rudbeckia hirta and Tradescantia ohiensis were 

exceptions to this trend. 

Five species had significant interactions between planting method and seed mix diversity (fig. 17). Again, species in 

the extra-high diversity mix were generally less frequent than 

those in the lower diversity mixes, with R. hirta an exception. 

Of these species, Heliopsis helianthoides tended to do better in 

the dormant broadcast treatment, but the others were generally 

slightly better represented in the summer drill and summer 

broadcast.

Six species had significant interactions between planting method and site (fig. 18). Here again, and in contrast to 

results at the Minnesota sites, the summer planting methods 

often showed superior performance to the dormant broadcast 

method; however, substantial variation among the species 

suggests that methods tailored to individual species—for 

example, staggered planting times—may yield the best results. 

Four species, Verbena stricta, Dalea purpurea, Astragalus 

canadensis, and Stipa spartea, had significant three-way 

interactions among site, planting method, and diversity, which 

rendered the results difficult to interpret.
Figure 16. Species-specific responses to site and seed mix diversity at Iowa sites. Proportion refers to 

the proportion of plots in which the species was encountered to all plots in which the species was planted. 

Shown are least square means and standard errors. PROPORTION

0.0

0.2

0.4

0.6

0.8

1.0

1.2

PROPORTION

0.0

0.2

0.4

0.6

0.8

1.0

1.2

EXPLANATION

PROPORTION PROPORTION

0.0

0.2

0.4

0.6

0.8

1.0

SITE

HARMISON ORBWEAVER PRODUCTION

Extra-high

High

Medium

Low

Bouteloua curtipendula

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.2

SITE

HARMISON ORBWEAVER PRODUCTION

Elymus canadensis

Schizachyrium scoparium Zizia aurea

Asclepias verticillata Rudbeckia hirta

Tradescantia ohiensis

18 Evaluation of Restoration Methods to Minimize Canada Thistle (Cirsium arvense) Infestation
Figure 17. Species-specific responses to planting method and seed mix diversity at Iowa sites. Proportion 

refers to the proportion of plots in which the species was encountered to all plots in which the species was 

planted. Shown are least square means and standard errors. PROPORTION

0.0

0.2

0.4

0.6

0.8

1.0

1.2

PROPORTION

0.0

0.2

0.4

0.6

0.8

1.0

1.2

EXPLANATION

PROPORTION

0.0

0.2

0.4

0.6

0.8

1.0

SITE

DORMANT

BROADCAST

SUMMER

BROADCAST

SUMMER

DRILL

Extra-high

High

Medium

Low

1.2 Andropogon gerardii

SITE

DORMANT

BROADCAST

SUMMER

BROADCAST

SUMMER

DRILL

Heliopsis helianthoides

Zizia aurea Elymus virginicus

Rudbeckia hirta

Results and Discussion 19
Figure 18. Species-specific responses to planting method and site at Iowa study sites. Proportion refers to 

the proportion of plots in which the species was encountered to all plots in which the species was planted. 

Shown are least square means and standard errors. PROPORTION

0.0

0.2

0.4

0.6

0.8

1.0

1.2

PROPORTION PROPORTION

0.0

0.2

0.4

0.6

0.8

1.0

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.2

SITE

HARMISON ORBWEAVER PRODUCTION

SITE

HARMISON ORBWEAVER PRODUCTION

Astragalus canadensis Bouteloua curtipendula

Echinacea pallida

Ratibida pinnata Stipa spartea

Dormant broadcast

EXPLANATION

Summer broadcast

Summer drill

Lespedeza capitata

20 Evaluation of Restoration Methods to Minimize Canada Thistle (Cirsium arvense) Infestation
Figure 19. Hypothesized model for effects of soil characteristics 

on Canada thistle cover. Straight arrows are causal pathways; 

curved arrows represent correlations between variables.

% Sand

Thistle cover

2005 (log)

% Clay Nitrification

Thistle cover

2006 (log)

Thistle cover

2007 (log)

Planted cover

2006 (log)

Synthesis 21

Synthesis

The results presented so far suggest that the dormant 

broadcast planting method will tend to optimize the establishment of planted species at Minnesota sites, regardless of site 

or diversity of the seed mix. At the Iowa sites, richness of the 

planted species tended to be optimized by the summer drill 

method, at least for low through high diversity seed mixes. 

Cover of planted species, on the other had, was highest for the 

dormant broadcast plots at sites in both Minnesota and Iowa. 

Higher diversity seed mixes, at least through approximately 

34 species, resulted in greater species richness; results from 

the extra-high diversity mix at the Iowa sites suggest that there 

may be a maximum seed mix diversity, above which there 

is not only no gain in richness but indeed a loss in realized 

species richness and cover of planted species. The importance of this deficit in native recruitment is not yet clear; if 

more “conservative” seeds germinate in subsequent years, the 

higher diversity may ultimately prove to be the more resilient 

to invasion.

Results with respect to Canada thistle are less straightforward. No single planting method or seed diversity level 

resulted in consistently lower infestations of Canada thistle 

across sites. To begin to understand the relations among sitespecific variables, such as soil texture and nitrogen cycling, 

and the response variable, abundance of Canada thistle, I used 

structural equation models (McCune and Grace, 2002) for the 

Minnesota sites. I took a model-generating approach (Jöreskog 

and Sörbom, 1996) to develop the model with data from 2005 

to 2007 with the aim of understanding what factors most influenced Canada thistle cover in 2007. I started with a model that 

included percent sand, percent clay, and nitrification, as well 

as Canada thistle cover in 2005, 2006, and 2007 and cover of 

planted species in 2006 (fig. 19). 

Minnesota Sites

Because nitrification was never significant for either the 

full model or the multigroup model (in which model structure and parameters were compared among the three planting 

methods), I removed it from the model. Likewise, I removed 

pathways that were never significant and for which I had no 

compelling biological rationale for their preservation. The 

resulting model (fig. 20) fit the data well for all three planting 

methods (Chi-square = 16.73, df = 12, P = 0.160). The total 

standardized effects point out several useful patterns in the 

data (table 6). First, cover of planted species in 2006 had a 

weak but significant negative effect on thistle cover in 2007 in 

both the dormant broadcast and summer drill plots; the effect 

was not significant in the summer broadcast plots (fig. 20). 

This result suggests that cover of planted species had already 

begun to influence Canada thistle populations, at least in these 

two planting methods.

Second, the negative effect of percent sand on cover of 

planted species was much larger in plots that were planted in 

the summer than in the dormant season plots (fig. 20), probably because of reduced water availability in sandy soils. Sandy 

sites may therefore benefit from a dormant broadcast planting 

method because increased cover of planted species ultimately 

also should mean less cover of Canada thistle (table 6). In 

contrast, clay strongly favored Canada thistle in all three planting methods.

Third, thistle cover in 2006 strongly influenced thistle 

cover in 2007 in all three planting methods; the effect of 2005 

on 2006 Canada thistle cover was not as strong (table 6). The 

implication of this result is that Canada thistle is not (yet, at 

least) regulated by density dependence. It would be tempting to conclude that, given the strong influence of previous 

thistle cover on subsequent thistle cover, rapid control of 

incipient infestations would benefit new restorations. Canada 

thistle cover, however, did not increase between 2006 and 

2007 at two study sites (Fahl and Meeker; fig. 5), and no 

control efforts were mounted at these sites. Future surveys, 

planned for 2009, will help discern if, by improving cover and 

diversity of planted species, managers can adequately control 

Canada thistle without resorting to herbicides or other disruptive methods.

Iowa Sites

Canada thistle occurred on only 12 of 110 plots for which 

we have soil data at Neal Smith NWR in 2007. (By contrast, 

116 of 214 plots with soil data in Minnesota contained Canada 

thistle in 2007.) Five of the 12 Iowa plots had been infested 

in 2006, but none of these had been infested in 2005. The 
Figure 20. Structural equation models for dormant broadcast (

A), summer broadcast (

B), and summer drill (

C) planting methods at Minnesota sites. Dotted lines refer 

to nonsignificant pathways; solid lines refer to significant pathways. Numbers next to lines are the standardized path coefficients; numbers next to variables in boxes are the coefficients of variation for those variables.

% Sand

Thistle cover

2005 (log)

% Clay

Thistle cover

2006 (log)

Thistle cover

2007 (log)

Planted cover

2006 (log)

-.87

-.43 -.28 .18

.01

.54

.32

.32

.82

.55 -.19

.08

.01

.03.22

% Sand

Thistle cover

2005 (log)

% Clay

Thistle cover

2006 (log)

Thistle cover

2007 (log)

Planted cover

2006 (log)

-.89

-.14 -.67 .21

.47

.40

.10

.40

.70

.59 -.13

.45

.04

.04.06

% Sand

Thistle cover

2005 (log)

% Clay

Thistle cover

2006 (log)

Thistle cover

2007 (log)

Planted cover

2006 (log)

-.90

-.32 -.70 .24

.21

.49

.25

.40

.76

.58 -.16

.49

.02

.06.03

22 Evaluation of Restoration Methods to Minimize Canada Thistle (Cirsium arvense) Infestation
Table 6. Standardized total effects for the dormant broadcast, summer broadcast, and summer drill planting methods at Minnesota 

sites. 

[Total effects take into account all the path coefficients between the variable in the column title and the variable in the row title (refer to fig. 14 to see the paths 

between the variables). For example, the total effect of percent (%) clay on thistle cover in 2007 dormant broadcast plots was 0.562, which means that for every 

increase of 1 standard deviation in percent clay, thistle cover in 2007 increased by 0.562 standard deviations. Entries of 0.000 indicate paths that were not present in the model]

Response

variable % Clay Thistle cover2005 % Sand Thistle cover2006

Planted cover

2006

Dormant broadcast

Thistle cover 2005 0.176 0.000 0.000 0.000 0.000

Thistle cover 2006 .046 .323 -.432 .000 .000

Planted cover 2006 .000 .000 -.284 .000 .000

Thistle cover 2007 .562 .177 -.182 .547 -.194

Summer broadcast

Thistle cover 2005 0.211 0.000 0.000 0.000 0.000

Thistle cover 2006 .493 .104 -.141 .000 .000

Planted cover 2006 .000 .000 -.668 .000 .000

Thistle cover 2007 .688 .061 .003 .585 -.128

Summer drill

Thistle cover 2005 0.242 0.000 0.000 0.000 0.000

Thistle cover 2006 .271 .252 -.318 .000 .000

Planted cover 2006 .000 .000 -.700 .000 .000

Thistle cover 2007 .651 .146 -.075 .581 -.158

References 23

two plots that had Canada thistle in 2005 were free of thistle 

in 2006 and 2007. Under these circumstances, any statistical 

model for the Iowa sites would be tenuous at best and likely 

to lead to false conclusions. It would seem that there is a 

strong component of chance with respect to infestation at Neal 

Smith NWR, which suggests that a landscape perspective may 

be valuable in understanding Canada thistle establishment. 

Because the study sites at Neal Smith NWR are surrounded 

by refuge lands, their proximity to thistle propagules may be 

substantially less than that of the Minnesota sites, which are 

surrounded by agricultural lands, roads, irrigation ditches, and 

the like.

Acknowledgments

J. Larson and K. Wahl worked long hours in the field 

to collect the data that form the basis of this report, and I am 

grateful for their dedication. M. Sovada, R. Gleason, and 

J. Grace provided comments on a previous draft that improved 

the clarity of this report.

References

Jöreskog, K.G., and Sörbom, D., 1996, LISREL 8—user’s 

reference guide: Chicago, Scientific Software International.

McCune, B., and Grace, J.B., 2002, Analysis of ecological 

communities: Gleneden Beach, Oreg., MjM Software 

Design.

U.S. Fish and Wildlife Service, 1999, Fulfilling the promise—

the National Wildlife Refuge System, visions for wildlife, 

habitat, people, and leadership: Arlington, Va., U.S. Fish 

and Wildlife Service.

Appendixes
26 Evaluation of Restoration Methods To Minimize Canada Thistle (Cirsium arvense) Infestation Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued [DF, degrees of freedom; SS, sums of squares] Variable Source DF Type III SS Mean square F value P value Reference table or figure Sand (Minn.) field 5 21,526.922 4,305.3844 259.33 <0.0001 fig. 1 Clay (Minn.) field 5 8,292.5578 1,658.5116 396.99 <.0001 fig. 1 Nitrogen mineralization (Minn.) field 5 3.0564167 .6112833 20.92 <.0001 table 1 Nitrification (Minn.) field 5 26.302954 5.2605908 17.91 <.0001 table 1 Sand (Iowa) field 2 4,136.664 2,068.332 51.6 <.0001 fig. 1 Clay (Iowa) field 2 386.31769 193.15884 27.25 <.0001 fig. 1 Nitrogen mineralization (Iowa) field 2 .4569387 .2284694 7.77 .0007 table 1 Nitrification (Iowa) field 2 3.8760873 1.9380437 31.44 <.0001 table 1 Thistle stems (Minn.) time 2 455,070.3 227,535.15 378.94 <.0001 fig. 2 time*site 10 448,881.84 44,888.185 74.76 <.0001 time*method 4 10,194.527 2,548.6318 4.24 .002 time*diversity 4 4,055.3033 1,013.8258 1.69 .1503 time*method*diversity 8 5,039.7591 629.9699 1.05 .3968 time*site*diversity 20 10,510.546 525.5273 .88 .6198 time*site*method 20 34,199.321 1,709.966 2.85 <.0001 fig. 3 time*site*method*diversity 40 18,150.649 453.7662 .76 .8659 error(time) 1,162 697,728.72 600.455 Thistle cover (Minn.) time 2 158,366.98 79,183.49 353.66 <.0001 time*site 10 145,300.15 14,530.015 64.9 <.0001 time*method 4 2,111.0438 527.7609 2.36 .0519 time*diversity 4 73.1075 18.2769 .08 .988 time*method*diversity 8 1,504.0752 188.0094 .84 .5676

time*site*diversity 20 2,420.8419 121.0421 .54 .9501

time*site*method 20 13,064.728 653.2364 2.92 <.0001 fig. 5

time*site*method*diversity 40 4,564.045 114.1011 .51 .9954

error(time) 1,178 263,747.61 223.8944
Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued

[DF, degrees of freedom; SS, sums of squares]

Variable Source DF Type III SS Mean square F value P value Reference table or figure

Cover of planted species 

(Minn.)

time 2 1,657,100.9 828,550.46 5,433.61 <0.0001time*site 10 82,791.485 8,279.148 54.29 <.0001time*method 4 14,085.451 3,521.363 23.09 <.0001time*diversity 4 2,662.757 665.689 4.37 .0017 fig. 8

time*method*diversity 8 2,073.077 259.135 1.7 .0942time*site*diversity 20 2,744.104 137.205 .9 .5877time*site*method 20 30,725.239 1,536.262 10.07 <.0001 fig. 7time*site*method*diversity

40 5,685.824 142.146 .93 .5925

error(time) 1,178 179,628.56 152.486

Thistle stems (Iowa) time 2 1,387.8434 693.92171 26.83 <.0001

time*site 4 927.58399 231.896 8.97 <.0001 fig. 2

time*method 4 556.64002 139.16001 5.38 .0003time*diversity 6 238.89879 39.81647 1.54 .1622time*method*diversity 12 673.42692 56.11891 2.17 .0115 fig. 4

time*site*diversity 12 303.37791 25.28149 .98 .4685time*site*method 8 590.07078 73.75885 2.85 .0039 fig. 3

time*site*method*diversity 24 821.89777 34.24574 1.32 .1375error(time) 784 20,273.53 25.85909

Thistle cover (Iowa) time 2 1,387.8434 693.92171 26.83 <.0001

time*site 4 927.58399 231.896 8.97 <.0001

time*method 4 556.64002 139.16001 5.38 .0003

time*diversity 6 238.89879 39.81647 1.54 .1622

time*method*diversity 12 673.42692 56.11891 2.17 .0115 fig. 6

time*site*diversity 12 303.37791 25.28149 .98 .4685

time*site*method 8 590.07078 73.75885 2.85 .0039 fig. 5

time*site*method*diversity 24 821.89777 34.24574 1.32 .1375

error(time) 784 20,273.53 25.85909

Appendix 127
28 Evaluation of Restoration Methods To Minimize Canada Thistle (Cirsium arvense) Infestation Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued [DF, degrees of freedom; SS, sums of squares] Variable Source DF Type III SS Mean square F value P value Reference table or figure Cover of planted species (Iowa) time 2 715,892.13 357,946.06 1,910.23 <0.0001 time*site 4 43,823.534 10,955.883 58.47 <.0001 fig. 9 time*method 4 14,770.297 3,692.5743 19.71 <.0001 time*diversity 6 54,769.826 9,128.3043 48.71 <.0001 time*method*diversity 12 7,082.3988 590.1999 3.15 .0002 fig. 10 time*site*diversity 12 4,034.3185 336.1932 1.79 .0451 time*site*method 8 675.9155 84.4894 .45 .8903 time*site*method*diversity 24 3,936.4474 164.0186 .88 .6375 error(time) 792 148,407.82 187.3836 Richness of planted species (Minn.) site 5 2,115.0245 423.0049 59.12 <.0001 method 2 2,383.1065 1191.5533 166.54 <.0001 diversity 2 5,870.0834 2,935.0417 410.23 <.0001 site*method 10 760.02355 76.002355 10.62 <.0001 site*diversity 10 522.65221 52.265221 7.31 <.0001 method*diversity 4 459.39597 114.84899 16.05 <.0001 site*method*diversity 20 329.05834 16.452917 2.3 .0011 fig. 11 Richness of planted species - Iowa site 2 60.847222 30.423611 2.49 .084 method 2 54.347222 27.173611 2.23 .1093 diversity 3 2,246.2847 748.76157 61.35 <.0001 site*method 4 7.888889 1.972222 .16 .9576 site*diversity 6 387.70833 64.618056 5.29 <.0001 fig. 12 method*diversity 6 185.09722 30.849537 2.53 .0206 fig. 12

site*method*diversity 12 94.888889 7.907407 .65 .8009
Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued

[DF, degrees of freedom; SS, sums of squares]

Variable Source DF Type III SS Mean square F value P value Reference table or figure

Minnesota: low diversity seed mix

Elymus canadensis field 5 0.0123354 0.0024671 0.8 0.5513

method 2 .0030761 .001538 .5 .6083diversity 2 .0123353 .0061677 1.99 .1369field*method 10 .0339404 .003394 1.1 .3614field*diversity 10 .0246811 .0024681 .8 .6305method*diversity 4 .0061625 .0015406 .5 .737field*method*diversity 20 .0678912 .0033946 1.1 .3466

Andropogon gerardii field 5 10.12031 2.024062 32.23 <.0001

method 2 5.4276292 2.7138146 43.21 <.0001diversity 2 .0806323 .0403161 .64 .5266

field*method 10 10.606116 1.0606116 16.89 <.0001 fig. 13field*diversity 10 .8659045 .0865905 1.38 .1861method*diversity 4 .3548754 .0887189 1.41 .2283field*method*diversity 20 1.5957348 .0797867 1.27 .1919

Bouteloua curtipendula field 5 8.8376826 1.7675365 15.25 <.0001

method 2 3.1305159 1.5652579 13.51 <.0001diversity 2 .1838343 .0919171 .79 .4529

field*method 10 12.250295 1.2250295 10.57 <.0001 fig. 13field*diversity 10 .5786612 .0578661 .5 .8908method*diversity 4 .3671357 .0917839 .79 .5306

field*method*diversity 20 1.7266777 .0863339 .74 .7799

Monarda fistulosa field 5 22.372154 4.4744307 41.42 <.0001

method 2 2.282012 1.141006 10.56 <.0001diversity 2 .333435 .1667175 1.54 .2145

field*method 10 6.5375387 .6537539 6.05 <.0001 fig. 13

field*diversity 10 1.305904 .1305904 1.21 .2818

method*diversity 4 .3348444 .0837111 .77 .5417

field*method*diversity 20 2.3681077 .1184054 1.1 .3485

Appendix 129
30 Evaluation of Restoration Methods To Minimize Canada Thistle (Cirsium arvense) Infestation Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued [DF, degrees of freedom; SS, sums of squares] Variable Source DF Type III SS Mean square F value P value Reference table or figure Minnesota: low diversity seed mix—Continued Helianthus maximiliani field 5 14.889545 2.977909 27.83 <0.0001 fig. 13 method 2 6.8312544 3.4156272 31.92 <.0001 diversity 2 3.7625013 1.8812506 17.58 <.0001 field*method 10 4.8695565 .4869557 4.55 <.0001 field*diversity 10 2.6298965 .2629897 2.46 .007 method*diversity 4 .9993553 .2498388 2.33 .0544 field*method*diversity 20 2.8869559 .1443478 1.35 .1416 Verbena stricta field 5 3.6867155 .7373431 4.25 .0008 method 2 34.501616 17.250808 99.4 <.0001 diversity 2 6.1138842 3.0569421 17.61 <.0001 field*method 10 3.6691501 .366915 2.11 .0217 field*diversity 10 4.17995 .417995 2.41 .0082 method*diversity 4 .209874 .0524685 .3 .8764 field*method*diversity 20 5.8237197 .291186 1.68 .0326 Dalea purpurea field 5 42.455657 8.4911314 53.92 <.0001 method 2 3.9224855 1.9612427 12.45 <.0001 diversity 2 3.350501 1.6752505 10.64 <.0001 table 2 field*method 10 10.410178 1.0410178 6.61 <.0001 fig. 13 field*diversity 10 2.4473146 .2447315 1.55 .1167 method*diversity 4 .2524014 .0631004 .4 .8082 field*method*diversity 20 2.426913 .1213457 .77 .7505

Schizachyrium scoparium field 5 6.5528265 1.3105653 6.94 <.0001

method 2 8.5668761 4.2834381 22.67 <.0001diversity 2 .6019867 .3009934 1.59 .2042

field*method 10 23.891609 2.3891609 12.64 <.0001 fig. 13

field*diversity 10 1.8311474 .1831147 .97 .4692

method*diversity 4 .7807563 .1951891 1.03 .3894

field*method*diversity 20 4.4105715 .2205286 1.17 .2771
Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued

[DF, degrees of freedom; SS, sums of squares]

Variable Source DF Type III SS Mean square F value P value Reference table or figure

Minnesota: low diversity seed mix—Continued

Aster novae-angliae field 5 13.818237 2.7636473 19.23 <0.0001

method 2 45.295901 22.64795 157.6 <.0001diversity 2 3.9299426 1.9649713 13.67 <.0001 table 2

field*method 10 4.9070813 .4907081 3.41 .0002 fig. 13

field*diversity 10 1.5479018 .1547902 1.08 .3776method*diversity 4 .2724451 .0681113 .47 .7549field*method*diversity 20 3.4132579 .1706629 1.19 .2585

Sorghastrum nutans field 5 7.8908534 1.5781707 13.75 <.0001

method 2 25.817209 12.908605 112.45 <.0001diversity 2 .026941 .0134705 .12 .8893

field*method 10 13.812005 1.3812005 12.03 <.0001 fig. 13field*diversity 10 1.6738515 .1673852 1.46 .1513method*diversity 4 .3064191 .0766048 .67 .6149field*method*diversity 20 2.3120229 .1156012 1.01 .4514

Minnesota: medium diversity seed mix

Heliopsis helianthoides field 5 3.6985629 0.7397126 7.76 <0.0001

method 2 .1402277 .0701138 .74 .4798

diversity 1 1.3099 1.3099 13.75 .0002 table 2field*method 10 .9715318 .0971532 1.02 .4258field*diversity 5 .4817439 .0963488 1.01 .4107method*diversity 2 .1251523 .0625761 .66 .5191

field*method*diversity 10 1.3464634 .1346463 1.41 .1719

Appendix 131
32 Evaluation of Restoration Methods To Minimize Canada Thistle (Cirsium arvense) Infestation Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued [DF, degrees of freedom; SS, sums of squares] Variable Source DF Type III SS Mean square F value P value Reference table or figure Minnesota: medium diversity seed mix—Continued Panicum virgatum field 5 23.721397 4.7442795 32.37 <0.0001 method 2 1.3553801 .6776901 4.62 .0104 diversity 1 .0048851 .0048851 .03 .8552 field*method 10 9.0035873 .9003587 6.14 <.0001 fig. 14 field*diversity 5 .2618517 .0523703 .36 .8775 method*diversity 2 .5884901 .2942451 2.01 .1357 field*method*diversity 10 1.6562967 .1656297 1.13 .3381 Coreopsis palmata field 5 15.08533 3.0170659 19.79 <.0001 method 2 21.086193 10.543097 69.16 <.0001 diversity 1 .7786429 .7786429 5.11 .0244 table 2 field*method 10 5.4007859 .5400786 3.54 .0002 fig. 14 field*diversity 5 .9269755 .1853951 1.22 .3007 method*diversity 2 .2380637 .1190319 .78 .4587 field*method*diversity 10 .9183009 .0918301 .6 .812 Artemisia ludoviciana field 5 11.103233 2.2206466 17.11 <.0001 method 2 28.520653 14.260326 109.88 <.0001 diversity 1 2.1160408 2.1160408 16.3 <.0001 field*method 10 8.7565371 .8756537 6.75 <.0001 field*diversity 5 .889739 .1779478 1.37 .2342 method*diversity 2 .8618027 .4309014 3.32 .0372 field*method*diversity 10 2.5660609 .2566061 1.98 .0345

Solidago rigida field 5 8.4166667 1.6833333 10.84 <.0001

method 2 29.926036 14.963018 96.37 <.0001diversity 1 1.3299748 1.3299748 8.57 .0036

field*method 10 2.2891523 .2289152 1.47 .1465

field*diversity 5 .4133417 .0826683 .53 .7518

method*diversity 2 .6779907 .3389953 2.18 .114

field*method*diversity 10 3.4799022 .3479902 2.24 .015
Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued

[DF, degrees of freedom; SS, sums of squares]

Variable Source DF Type III SS Mean square F value P value Reference table or figure

Minnesota: medium diversity seed mix—Continued

Dalea candida field 5 27.172649 5.4345298 38.57 <0.0001

method 2 2.7984049 1.3992025 9.93 <.0001diversity 1 .7556866 .7556866 5.36 .0211 table 2

field*method 10 12.323736 1.2323736 8.75 <.0001 fig. 14field*diversity 5 1.2046525 .2409305 1.71 .1312method*diversity 2 .4211715 .2105858 1.49 .2256field*method*diversity 10 2.1534433 .2153443 1.53 .1269

Lespedeza capitata field 5 15.868303 3.1736606 21.63 <.0001

method 2 6.9306761 3.4653381 23.62 <.0001diversity 1 1.4014388 1.4014388 9.55 .0021 table 2

field*method 10 10.995391 1.0995391 7.49 <.0001 fig. 14field*diversity 5 1.5981448 .319629 2.18 .0558method*diversity 2 .0574209 .0287105 .2 .8224field*method*diversity 10 1.3421344 .1342134 .91 .5195

Zizia aurea field 5 7.1571765 1.4314353 9.01 <.0001

method 2 8.4949923 4.2474962 26.74 <.0001diversity 1 .002309 .002309 .01 .9041

field*method 10 5.0023433 .5002343 3.15 .0007 fig. 14

field*diversity 5 .7872679 .1574536 .99 .4228method*diversity 2 .0879572 .0439786 .28 .7583

field*method*diversity 10 .9937226 .0993723 .63 .7922

Potentilla arguta field 5 8.9335248 1.786705 14.16 <.0001

method 2 12.990843 6.4954214 51.49 <.0001diversity 1 1.5718075 1.5718075 12.46 .0005 table 2field*method 10 4.3266952 .4326695 3.43 .0002 fig. 14

field*diversity 5 .1035165 .0207033 .16 .9755

method*diversity 2 .7215798 .3607899 2.86 .0584

field*method*diversity 10 1.4395852 .1439585 1.14 .3299

Appendix 133
34 Evaluation of Restoration Methods To Minimize Canada Thistle (Cirsium arvense) Infestation Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued [DF, degrees of freedom; SS, sums of squares] Variable Source DF Type III SS Mean square F value P value Reference table or figure Minnesota: medium diversity seed mix—Continued Sporobolus asper field 5 3.9211693 0.7842339 8.62 <0.0001 method 2 31.864391 15.932196 175.22 <.0001 diversity 1 .0577246 .0577246 .63 .4261 field*method 10 4.590312 .4590312 5.05 <.0001 fig. 14 field*diversity 5 .4246329 .0849266 .93 .4587 method*diversity 2 .2959241 .147962 1.63 .1978 field*method*diversity 10 .2564997 .02565 .28 .985 Minnesota: high diversity seed mix Elymus trachycaulus field 5 1.3703704 0.2740741 9.58 <0.0001 method 2 .4814815 .2407407 8.41 .0003 field*method 10 2.0185185 .2018519 7.05 <.0001 fig. 15 Ratibida columnifera field 5 10.208333 2.0416667 21.75 <.0001 method 2 1.1944444 .5972222 6.36 .0021 field*method 10 5.6388889 .5638889 6.01 <.0001 fig. 15 Rudbeckia hirta field 5 11.259259 2.2518519 14.08 <.0001 method 2 2.2314815 1.1157407 6.98 .0012 field*method 10 5.212963 .5212963 3.26 .0006 fig. 15 Solidago speciosa field 5 2.9814815 .5962963 4.69 .0005 method 2 2.3981482 1.1990741 9.43 .0001 field*method 10 2.0462963 .2046296 1.61 .1059 Stipa viridula field 5 11.148148 2.2296296 12.44 <.0001

method 2 2.8148148 1.4074074 7.85 .0005

field*method 10 4.5185185 .4518519 2.52 .0071 fig. 15

Desmodium canadense field 5 11.425926 2.2851852 14.07 <.0001

method 2 6.6759259 3.337963 20.55 <.0001field*method 10 3.6574074 .3657407 2.25 .0164 fig. 15
Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued

[DF, degrees of freedom; SS, sums of squares]

Variable Source DF Type III SS Mean square F value P value Reference table or figure

Minnesota: high diversity seed mix—Continued

Asclepias verticillata field 5 11.814815 2.362963 12.59 <0.0001

method 2 3.1203704 1.5601852 8.31 .0003

field*method 10 1.4351852 .1435185 .76 .6628

Echinacea angustifolia field 5 9.6527778 1.9305556 11.73 <.0001

method 2 4.1111111 2.0555556 12.49 <.0001field*method 10 2.6111111 .2611111 1.59 .1127

Iowa: low diversity seed mix

Elymus canadensis field 2 1.1435185 0.5717593 11.32 <0.0001

method 2 .2407407 .1203704 2.38 .0936

diversity 3 1.537037 .5123457 10.14 <.0001

field*method 4 .1342593 .0335648 .66 .6169

field*diversity 6 2.0046296 .3341049 6.62 <.0001 fig. 16method*diversity 6 .1296296 .0216049 .43 .8604field*method*diversity 12 .9953704 .0829475 1.64 .0777

Andropogon gerardii field 2 .0324074 .0162037 .15 .8612

method 2 .3101852 .1550926 1.43 .2403diversity 3 20.618056 6.8726852 63.42 <.0001

field*method 4 .0787037 .0196759 .18 .9479

field*diversity 6 .9861111 .1643519 1.52 .1713method*diversity 6 2.5416667 .4236111 3.91 .0008 fig. 17

field*method*diversity 12 .7916667 .0659722 .61 .8351

Bouteloua curtipendula field 2 1.1157407 .5578704 4.1 .0172

method 2 .4212963 .2106482 1.55 .2136

diversity 3 8.5740741 2.8580247 21.02 <.0001field*method 4 1.412037 .3530093 2.6 .036 fig. 18

field*diversity 6 2.1064815 .3510803 2.58 .0182 fig. 16

method*diversity 6 .5231482 .0871914 .64 .6971

field*method*diversity 12 2.087963 .1739969 1.28 .2276

Appendix 135
36 Evaluation of Restoration Methods To Minimize Canada Thistle (Cirsium arvense) Infestation Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued [DF, degrees of freedom; SS, sums of squares] Variable Source DF Type III SS Mean square F value P value Reference table or figure Iowa: low diversity seed mix—Continued Monarda fistulosa field 2 2.5740741 1.287037 5.91 0.0029 table 5 method 2 3.9490741 1.974537 9.07 .0001 table 4 diversity 3 5.5555556 1.8518519 8.51 <.0001 table 3 field*method 4 1.4537037 .3634259 1.67 .1561 field*diversity 6 2.0555556 .3425926 1.57 .1532 method*diversity 6 2.4027778 .400463 1.84 .0901 field*method*diversity 12 3.6944444 .3078704 1.41 .156 Helianthus occidentalis field 2 .0416667 .0208333 1.11 .3298 method 2 .0416667 .0208333 1.11 .3298 diversity 3 .3032407 .1010803 5.4 .0012 field*method 4 .125 .03125 1.67 .1565 field*diversity 6 .3842593 .0640432 3.42 .0027 method*diversity 6 .162037 .0270062 1.44 .1973 field*method*diversity 12 .337963 .0281636 1.5 .1198 Verbena stricta field 2 .0185185 .0092593 2.2 .1122 method 2 .0185185 .0092593 2.2 .1122 diversity 3 .0277778 .0092593 2.2 .0876 field*method 4 .037037 .0092593 2.2 .0683 field*diversity 6 .0555556 .0092593 2.2 .0422 method*diversity 6 .0555556 .0092593 2.2 .0422 field*method*diversity 12 .1111111 .0092593 2.2 .0112

Dalea purpurea field 2 1.6712963 .8356482 7.25 .0008

method 2 .837963 .4189815 3.63 .0273

diversity 3 1.8703704 .6234568 5.41 .0012

field*method 4 3.037037 .7592593 6.58 <.0001field*diversity 6 .6990741 .1165124 1.01 .418

method*diversity 6 .8657407 .1442901 1.25 .2792

field*method*diversity 12 2.6481482 .220679 1.91 .0313
Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued

[DF, degrees of freedom; SS, sums of squares]

Variable Source DF Type III SS Mean square F value P value Reference table or figure

Iowa: low diversity seed mix—Continued

Schizachyrium scoparium field 2 2.1435185 1.0717593 5.55 0.0042

method 2 3.6296296 1.8148148 9.39 .0001 table 4diversity 3 7.212963 2.404321 12.45 <.0001

field*method 4 1.2592593 .3148148 1.63 .1659

field*diversity 6 2.8009259 .466821 2.42 .0263 fig. 16

method*diversity 6 2.1481482 .3580247 1.85 .0877field*method*diversity 12 .962963 .0802469 .42 .9574

Aster novae-angliae field 2 .0324074 .0162037 .65 .5241

method 2 .1712963 .0856482 3.42 .0337diversity 3 .0625 .0208333 .83 .4769field*method 4 .037037 .0092593 .37 .8302field*diversity 6 .0972222 .0162037 .65 .6925method*diversity 6 .1805556 .0300926 1.2 .3044field*method*diversity 12 .2222222 .0185185 .74 .7126

Sorghastrum nutans field 2 .6666667 .3333333 1.86 .1568

method 2 2.375 1.1875 6.63 .0015 table 4diversity 3 13.358796 4.4529321 24.87 <.0001

field*method 4 .5833333 .1458333 .81 .5165

field*diversity 6 2.3703704 .3950617 2.21 .0417method*diversity 6 .9398148 .1566358 .87 .5135

field*method*diversity 12 1.6018519 .1334877 .75 .7067

Appendix 137
38 Evaluation of Restoration Methods To Minimize Canada Thistle (Cirsium arvense) Infestation Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued [DF, degrees of freedom; SS, sums of squares] Variable Source DF Type III SS Mean square F value P value Reference table or figure Iowa: medium diversity seed mix Artemisia ludoviciana field 2 0.1666667 0.0833333 2.48 0.0859 method 2 .2407407 .1203704 3.58 .0292 diversity 2 .1666667 .0833333 2.47 .0859 field*method 4 .2037037 .0509259 1.51 .1985 field*diversity 4 .2222222 .0555556 1.65 .1617 method*diversity 4 .0925926 .0231482 .69 .6011 field*method*diversity 8 .462963 .0578704 1.72 .0935 Coreopsis palmata field 2 .0432099 .0216049 .9 .4096 method 2 .0061728 .0030864 .13 .88 diversity 2 .154321 .0771605 3.2 .0423 field*method 4 .0864198 .0216049 .9 .467 field*diversity 4 .0493827 .0123457 .51 .7272 method*diversity 4 .1975309 .0493827 2.05 .0879 field*method*diversity 8 .0987654 .0123457 .51 .8474 Dalea candida field 2 2.8888889 1.4444444 7.92 .0004 table 5 method 2 .7962963 .3981482 2.18 .1145 diversity 2 3.2407407 1.6203704 8.88 .0002 table 3 field*method 4 1.7037037 .4259259 2.34 .0556 field*diversity 4 1.0925926 .2731482 1.5 .2028 method*diversity 4 .5185185 .1296296 .71 .5851 field*method*diversity 8 .5925926 .0740741 .41 .9167

Heliopsis helianthoides field 2 3.4506173 1.7253086 10.37 <.0001 table 5

method 2 4.1728395 2.0864198 12.54 <.0001diversity 2 6.8950617 3.4475309 20.72 <.0001field*method 4 .8827161 .220679 1.33 .2601

field*diversity 4 .6604938 .1651235 .99 .4119

method*diversity 4 3.8271605 .9567901 5.75 .0002 fig. 17

field*method*diversity 8 .9506173 .1188272 .71 .679
Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued

[DF, degrees of freedom; SS, sums of squares]

Variable Source DF Type III SS Mean square F value P value Reference table or figure

Iowa: medium diversity seed mix—Continued

Lespedeza capitata field 2 4.4506173 2.2253086 11.44 <0.0001

method 2 4.0246914 2.0123457 10.35 <.0001diversity 2 10.635802 5.3179012 27.35 <.0001 table 3

field*method 4 2.0308642 .5077161 2.61 .0357 fig. 18

field*diversity 4 .4197531 .1049383 .54 .7067method*diversity 4 .1790124 .0447531 .23 .9213field*method*diversity 8 1.4320988 .1790124 .92 .4996

Panicum virgatum field 2 1.3395062 .6697531 3.58 .0291 table 5

method 2 1.4876543 .7438272 3.97 .0198 table 4diversity 2 2.7098765 1.3549383 7.24 .0009 table 3field*method 4 .9753086 .2438272 1.3 .269field*diversity 4 1.1975309 .2993827 1.6 .1744method*diversity 4 .7160494 .1790124 .96 .4317field*method*diversity 8 1.4320988 .1790124 .96 .4703

Potentilla arguta field 2 1.462963 .7314815 8.78 .0002 table 5

method 2 1.1851852 .5925926 7.11 .001 table 4diversity 2 .2962963 .1481482 1.78 .1708field*method 4 .6851852 .1712963 2.06 .0867field*diversity 4 .3518519 .087963 1.06 .3788

method*diversity 4 .3518519 .087963 1.06 .3788

field*method*diversity 8 .5555556 .0694444 .83 .5738

Solidago rigida field 2 .2407407 .1203704 1.38 .2533

method 2 .462963 .2314815 2.65 .0721

diversity 2 .462963 .2314815 2.65 .0721

field*method 4 .462963 .1157407 1.33 .2601

field*diversity 4 .6851852 .1712963 1.96 .1001

method*diversity 4 .2962963 .0740741 .85 .4952

field*method*diversity 8 1.1111111 .1388889 1.59 .1266

Appendix 139
40 Evaluation of Restoration Methods To Minimize Canada Thistle (Cirsium arvense) Infestation Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued [DF, degrees of freedom; SS, sums of squares] Variable Source DF Type III SS Mean square F value P value Reference table or figure Iowa: medium diversity seed mix—Continued Sporobolus asper field 2 2.2283951 1.1141975 5.22 0.0059 table 5 method 2 10.395062 5.1975309 24.34 <.0001 table 4 diversity 2 1.3765432 .6882716 3.22 .0412 table 3 field*method 4 .1790124 .0447531 .21 .933 field*diversity 4 1.0864198 .2716049 1.27 .281 method*diversity 4 .308642 .0771605 .36 .836 field*method*diversity 8 .8950617 .1118827 .52 .8382 Zizia aurea field 2 3.1358025 1.5679012 10.09 <.0001 method 2 2.0432099 1.0216049 6.57 .0016 diversity 2 .8209877 .4104938 2.64 .073 field*method 4 .1604938 .0401235 .26 .9046 field*diversity 4 1.7160494 .4290124 2.76 .028 fig. 16 method*diversity 4 3.4197531 .8549383 5.5 .0003 fig. 17 field*method*diversity 8 .7098765 .0887346 .57 .8016 Iowa: high diversity seed mix Asclepias verticillata field 2 2.0833333 1.0416667 4.57 0.0114 method 2 .5277778 .2638889 1.16 .3159 diversity 1 .0046296 .0046296 .02 .8868 field*method 4 .3888889 .0972222 .43 .789 field*diversity 2 2.8425926 1.4212963 6.24 .0024 fig. 16 method*diversity 2 .8981482 .4490741 1.97 .1419

field*method*diversity 4 1.1296296 .2824074 1.24 .2951
Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued

[DF, degrees of freedom; SS, sums of squares]

Variable Source DF Type III SS Mean square F value P value Reference table or figure

Iowa: high diversity seed mix—Continued

Aster ericoides field 2 0.3611111 0.1805556 1.82 0.1651

method 2 .1944444 .0972222 .98 .3776diversity 1 .0185185 .0185185 .19 .6664field*method 4 .1944444 .0486111 .49 .7435field*diversity 2 .0648148 .0324074 .33 .722method*diversity 2 .1759259 .087963 .89 .4141field*method*diversity 4 .6574074 .1643519 1.65 .1621

Aster laevis field 2 .0092593 .0046296 .5 .6073

method 2 .0092593 .0046296 .5 .6073diversity 1 .0185185 .0185185 2 .1589field*method 4 .0462963 .0115741 1.25 .2911field*diversity 2 .0092593 .0046296 .5 .6073method*diversity 2 .0092593 .0046296 .5 .6073field*method*diversity 4 .0462963 .0115741 1.25 .2911

Echinacea pallida field 2 4.9259259 2.462963 14.93 <.0001

method 2 .1203704 .0601852 .36 .6948

diversity 1 .1666667 .1666667 1.01 .3161field*method 4 1.6851852 .4212963 2.55 .0403 fig. 18

field*diversity 2 .7777778 .3888889 2.36 .0973method*diversity 2 .1944444 .0972222 .59 .5557

field*method*diversity 4 .9444444 .2361111 1.43 .225

Elymus virginicus field 2 .1759259 .087963 1.05 .3536

method 2 .0648148 .0324074 .39 .681

diversity 1 35.851852 35.851852 425.92 <.0001field*method 4 .0740741 .0185185 .22 .9271

field*diversity 2 .1759259 .087963 1.05 .3536

method*diversity 2 .6203704 .3101852 3.69 .0268 fig. 17

field*method*diversity 4 .3518519 .087963 1.05 .3851

Appendix 141
42 Evaluation of Restoration Methods To Minimize Canada Thistle (Cirsium arvense) Infestation Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued [DF, degrees of freedom; SS, sums of squares] Variable Source DF Type III SS Mean square F value P value Reference table or figure Iowa: high diversity seed mix—Continued Pycnanthemum virginianum field 2 0.1944444 0.0972222 3 0.0521 method 2 .5277778 .2638889 8.14 .0004 diversity 1 .2268519 .2268519 7 .0088 field*method 4 .6111111 .1527778 4.71 .0012 field*diversity 2 .0648148 .0324074 1 .3697 method*diversity 2 .287037 .1435185 4.43 .0131 field*method*diversity 4 .2962963 .0740741 2.29 .0615 Ratibida pinnata field 2 .8425926 .4212963 2.26 .1071 method 2 1.787037 .8935185 4.79 .0093 diversity 1 10.226852 10.226852 54.85 <.0001 table 3 field*method 4 2.7685185 .6921296 3.71 .0061 fig. 18 field*diversity 2 .4537037 .2268519 1.22 .2984 method*diversity 2 .0092593 .0046296 .02 .9755 field*method*diversity 4 .4351852 .1087963 .58 .6749 Rudbeckia hirta field 2 .7777778 .3888889 2.04 .1322 method 2 3.0833333 1.5416667 8.1 .0004 diversity 1 1.5 1.5 7.88 .0055 field*method 4 1.1388889 .2847222 1.5 .2046 field*diversity 2 1.4444444 .7222222 3.8 .0241 fig. 16 method*diversity 2 7.6944444 3.8472222 20.22 <.0001 fig. 17 field*method*diversity 4 .0277778 .0069444 .04 .9974

Solidago speciosa field 2 1.8425926 .9212963 13.77 <.0001

method 2 .1481482 .0740741 1.11 .3326

diversity 1 .0046296 .0046296 .07 .7928

field*method 4 .1296296 .0324074 .48 .7473

field*diversity 2 .0648148 .0324074 .48 .6169

method*diversity 2 .037037 .0185185 .28 .7586

field*method*diversity 4 .1851852 .0462963 .69 .5984
Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued

[DF, degrees of freedom; SS, sums of squares]

Variable Source DF Type III SS Mean square F value P value Reference table or figure

Iowa: high diversity seed mix—Continued

Tradescantia ohiensis field 2 1.3333333 0.6666667 3.74 0.0256

method 2 2.1944444 1.0972222 6.15 .0026 table 4diversity 1 1.1851852 1.1851852 6.64 .0107field*method 4 .5555556 .1388889 .78 .5405field*diversity 2 1.9259259 .962963 5.4 .0052 fig. 16

method*diversity 2 .4537037 .2268519 1.27 .2828field*method*diversity 4 .3518519 .087963 .49 .7409

Tridens flavus field 2 .1111111 .0555556 1.06 .3469

method 2 .1944444 .0972222 1.86 .1579diversity 1 .2962963 .2962963 5.68 .0181field*method 4 .0277778 .0069444 .13 .9701field*diversity 2 .037037 .0185185 .35 .7017method*diversity 2 .287037 .1435185 2.75 .0664field*method*diversity 4 .0462963 .0115741 .22 .9261

Vernonia fasciculata field 2 .3425926 .1712963 2.38 .0952

method 2 .6203704 .3101852 4.31 .0147diversity 1 .0046296 .0046296 .06 .8field*method 4 .1574074 .0393519 .55 .7016field*diversity 2 .0648148 .0324074 .45 .6381method*diversity 2 .0648148 .0324074 .45 .6381

field*method*diversity 4 .1574074 .0393519 .55 .7016

Iowa: Extra-high diversity seed mix

Anemone cylindrica field 2 0.0740741 0.037037 0.31 0.7374

method 2 .6851852 .3425926 2.83 .064 table 4field*method 4 .8703704 .2175926 1.8 .1358

Asclepias tuberosa field 2 1.4074074 .7037037 3.72 .0278 table 5

method 2 4.0185185 2.0092593 10.61 <.0001field*method 4 1.7037037 .4259259 2.25 .0692 fig. 18

Appendix 143
44 Evaluation of Restoration Methods To Minimize Canada Thistle (Cirsium arvense) Infestation Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued [DF, degrees of freedom; SS, sums of squares] Variable Source DF Type III SS Mean square F value P value Reference table or figure Iowa: Extra-high diversity seed mix—Continued Astragalus canadensis field 2 0.3888889 0.1944444 1.38 0.2556 method 2 .3888889 .1944444 1.38 .2556 field*method 4 2.2222222 .5555556 3.95 .0051 Baptisia leucantha field 2 .6851852 .3425926 1.55 .2166 method 2 .7962963 .3981482 1.81 .1698 field*method 4 1.8703704 .4675926 2.12 .0839 Cassia fasciculata field 2 .5185185 .2592593 1.29 .2787 method 2 .0185185 .0092593 .05 .9549 field*method 4 .3703704 .0925926 .46 .7633 Delphinium virescens field 2 2.462963 1.2314815 7.91 .0007 table 5 method 2 .9074074 .4537037 2.91 .059 field*method 4 .4259259 .1064815 .68 .6048 Desmodium canadense field 2 1.462963 .7314815 3.64 .0299 table 5 method 2 2.7962963 1.3981482 6.95 .0015 table 4 field*method 4 1.2592593 .3148148 1.56 .1896 Eryngium yuccifolium field 2 .1296296 .0648148 1.57 .2129 method 2 .2407407 .1203704 2.92 .0587 field*method 4 .3148148 .0787037 1.91 .115 Helenium autumnale field 2 .5185185 .2592593 3.08 .0504 method 2 .0740741 .037037 .44 .6453 field*method 4 .1481482 .037037 .44 .7794

Parthenium integrifolium field 2 .9074074 .4537037 1.92 .1523

method 2 1.1851852 .5925926 2.51 .0868

field*method 4 1.2592593 .3148148 1.33 .2638

Penstemon digitalis field 2 .5740741 .287037 5.25 .0068

method 2 .1296296 .0648148 1.18 .3102

field*method 4 .4259259 .1064815 1.95 .1087
Appendix 1. Analysis of variance (ANOVA) tables for statistical tests.—Continued

[DF, degrees of freedom; SS, sums of squares]

Variable Source DF Type III SS Mean square F value P value Reference table or figure

Iowa: Extra-high diversity seed mix—Continued

Ruellia humilis field 2 0.6666667 0.3333333 3.41 0.0368

method 2 .0555556 .0277778 .28 .753field*method 4 .2777778 .0694444 .71 .5862

Stipa spartea field 2 2.0185185 1.0092593 6.09 .0032

method 2 .2962963 .1481482 .89 .4125field*method 4 2.4814815 .6203704 3.74 .0071 fig. 18

Thalictrum dasycarpum field 2 4.962963 2.4814815 13.91 <.0001 table 5

method 2 .5740741 .287037 1.61 .2054field*method 4 .0925926 .0231482 .13 .9713

Appendix 145
46 Evaluation of Restoration Methods To Minimize Canada Thistle (Cirsium arvense) Infestation

Appendix 2. Species in the Minnesota seed mixes. 

[N refers to the number of plots in which the species was encountered; proportion refers to the number of plots 

in which the species was encountered divided by the number of plots in which the species was planted. For all 

mixes, the maximum number of plots is 648; for medium and high, 432; and for high, 216]

Seed mix diversity Species N Proportion

All Andropogon gerardii 573 0.88

All Aster novae-angliae 277 .43

All Bouteloua curtipendula 531 .82

All Dalea purpurea 279 .43

All Elymus canadensis 646 1.00

All Helianthus maximiliani 523 .81

All Monarda fistulosa 525 .81

All Schizachyrium scoparium 279 .43

All Sorghastrum nutans 159 .25

All Verbena stricta 301 .46

Medium and High Artemisia ludoviciana 252 .58

Medium and High Coreopsis palmata 255 .59

Medium and High Dalea candida 180 .42

Medium and High Heliopsis helianthoides 403 .93

Medium and High Lespedeza capitata 150 .35

Medium and High Panicum virgatum 300 .69

Medium and High Potentilla arguta 114 .26

Medium and High Solidago rigida 218 .50

Medium and High Sporobolus asper 104 .24

Medium and High Zizia aurea 118 .27

High Allium stellatum 27 .13

High Asclepias verticillata 104 .48

High Aster laevis 19 .09

High Carex bicknellii 0 .00

High Carex vulpinoidea 5 .02

High Desmodium canadense 111 .51

High Echinacea angustifolia 77 .36

High Elymus trachycaulus 240 1.11

High Liatris aspera 0 .00

High Ratibida columnifera 180 .83

High Rudbeckia hirta 158 .73

High Solidago speciosa 131 .61

High Stipa viridula 116 .54

High Vernonia fasciculata 14 .06
Appendix 3. Species in the Iowa seed mixes.—Continued

[N refers to the number of plots in which the species was encountered; proportion refers to the number of plots in which 

the species was encountered divided by the number of plots in which the species was planted. For all mixes, the maximum number of plots is 432; for medium to extra-high, 324; for high and extra-high, 216; and for extra-high, 108]

Seed mix diversity Species N Proportion

All Andropogon gerardii 347 0.80

All Aster novae-angliae 11 .03

All Bouteloua curtipendula 344 .80

All Dalea purpurea 68 .16

All Elymus canadensis 404 .94

All Helianthus occidentalis 9 .02

All Monarda fistulosa 224 .52

All Schizachyrium scoparium 146 .34

All Sorghastrum nutans 297 .69

All Verbena stricta 2 .00

Medium to Extra-high Artemisia ludoviciana 12 .04

Medium to Extra-high Coreopsis palmata 8 .02

Medium to Extra-high Dalea candida 92 .28

Medium to Extra-high Heliopsis helianthoides 232 .72

Medium to Extra-high Lespedeza capitata 177 .55

Medium to Extra-high Panicum virgatum 241 .74

Medium to Extra-high Potentilla arguta 34 .10

Medium to Extra-high Solidago rigida 35 .11

Medium to Extra-high Sporobolus asper 162 .50

Medium to Extra-high Zizia aurea 258 .80

High and Extra-high Asclepias verticillata 126 .58

High and Extra-high Aster ericoides 43 .20

High and Extra-high Aster laevis 3 .01

High and Extra-high Echinacea pallida 169 .78

High and Extra-high Elymus virgincus 131 .61

High and Extra-high Liatris aspera 1 .00

High and Extra-high Phlox pilosa 0 .00

High and Extra-high Pycnanthemum virginianum 9 .04

High and Extra-high Ratibida pinnata 130 .60

High and Extra-high Rudbeckia hirta 142 .66

High and Extra-high Solidago speciosa 17 .08

High and Extra-high Tradescantia ohiensis 61 .28

High and Extra-high Tridens flavus 20 .09

High and Extra-high Vernonia fasciculata 19 .09

Extra-high Amorpha canescens 0 .00

Extra-high Anemone cylindrica 23 .21

Extra-high Asclepias tuberosa 47 .44

Extra-high Aster azureus 0 .00

Extra-high Astragalus canadensis 22 .20

Extra-high Baptisia leucantha 75 .69

Extra-high Cassia fasciculata 147 1.36

Extra-high Coreopsis tripteris 0 .00

Appendix 3 47
48 Evaluation of Restoration Methods to Minimize Canada Thistle (Cirsium arvense) Infestation

Appendix 3. Species in the Iowa seed mixes.—Continued

[N refers to the number of plots in which the species was encountered; proportion refers to the number of plots in which 

the species was encountered divided by the number of plots in which the species was planted. For all mixes, the maximum number of plots is 432; for medium to extra-high, 324; for high and extra-high, 216; and for extra-high, 108]

Seed mix diversity Species N Proportion

Extra-high Delphinium virescens 25 0.23

Extra-high Desmodium canadense 44 .41

Extra-high Eryngium yuccifolium 5 .05

Extra-high Gentiana flavida 0 .00

Extra-high Helenium autumnale 11 .10

Extra-high Heuchera richardsonii 1 .01

Extra-high Liatris pycnostachya 1 .01

Extra-high Parthenium integrifolium 61 .56

Extra-high Penstemon digitalis 7 .06

Extra-high Ruellia humilis 16 .15

Extra-high Sporobolus heterolepis 0 .00

Extra-high Stipa spartea 30 .28

Extra-high Thalictrum dasycarpum 35 .32

Extra-high Tradescantia bracteata 0 .00

Extra-high Veronicastrum virginicum 1 .01

Extra-high Viola pedatifida 2 .02

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For more information concerning this publication, contact:

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Jamestown, North Dakota 58401

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Or visit the Northern Prairie Wildlife Research Center Web site at:

http://www.npwrc.usgs.gov/

Larson—Evaluation of Restoration Methods to Minimize Canada Thistle (Cirsium arvense) Infestation—Open-File Report 2009–1130

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