identification guide to the weeds of quebec by CRAAQ

Second Edition

Identification Guide to the Weeds of Quebec

Author of the second edition

Amélie Picard, M.Sc., agr., agronomist, weed scientist, Laboratoire d’expertise et de diagnostic en phytoprotection, Direction de la phytoprotection, Ministère de l’Agriculture, des Pêcheries et de l’Alimentation

Revision

Annie Marcoux, M.Sc., agr., agronomist, Laboratoire d’expertise et de diagnostic en phytoprotection, Direction de la phytoprotection, ministère de l’Agriculture, des Pêcheries et de l’Alimentation

Authors of the first edition

Claude J. Bouchard and Romain Néron

Ce projet a été financé par l’entremise du volet 1 du programme Prime-Vert, mis en œuvre en vertu du Partenariat canadien pour l’agriculture, selon une entente conclue entre les gouvernements du Canada et du Québec.

Second

Edition

COORDINATION, EDITING, GRAPHIC DESIGN AND LAYOUT BY THE CRAAQ

Karine Beaupré, Operations and Customer Service Coordinator

Gisèle Bertrand, Communications and Knowledge Mobilization Advisor

Lyne Lauzon, Publications Project Manager

Nathalie Nadeau, Graphic Designer

Véronique Michaud, Graphic Designer

TRANSLATION INTO ENGLISH

Confluence Communication: www.confluence-communication.ca

The reproduction, translation, or adaption of this Guide is prohibited without written authorization from the Centre de référence en agriculture et agroalimentaire du Québec, in order to respect copyright and encourage the dissemination of new knowledge.

WARNINGS

At the time of writing, the information contained in this Guide was considered representative of knowledge of weed identification in Quebec. Its use is entirely the responsibility of the reader.

For information and comments

Centre de référence en agriculture et agroalimentaire du Québec (CRAAQ)

Édifice Delta 1, 2875, boulevard Laurier, 9e étage

Québec (Québec) G1V 2M2

418 523-5411 | 1 888 535-2537 | www.craaq.qc.ca | client@craaq.qc.ca

PEDI0221

ISBN 978-2-7649-0663-7 (Second Edition)

ISBN 978-2-7649-0665-1 (PDF)

ISBN 978-2-7649-0662-0 (Second Edition in French)

ISBN 978-2-7649-0664-4 (PDF in French)

(Original in French: ISBN 2-89457-162-3)

ISBN 2-89457-174-7 (First Edition, 1999)

Legal deposit

Library and Archives Canada, 2023

Bibliothèque et Archives nationales du Québec, 2023

A plant cannot be bad in and of itself. It becomes a weed when it interferes with the growth of crops, by being in the wrong place at the wrong time.

PREFACE

This guide is the second edition of the Identification Guide to the Weeds of Quebec, written by Claude J. Bouchard and Romain Néron and published in 1998. Since it was widely used in the field and consulted as a reference work, it became crucial to republish the Guide to update its contents and images.

New species have been added to better meet users’ needs. In addition, most of the images in the Guide have been updated to emphasize the features that help identify species.

To facilitate work in the field, the identification keys have also been updated. These will help readers identify weeds at the seedling and vegetative stages of growth, which are often the most difficult for species identification.

ACKNOWLEDGEMENTS

The author would like to thank all those who have contributed directly or indirectly to the republication of the Guide. She also would like to acknowledge the members of MAPAQ’s weed science team at the Laboratoire d’expertise et de diagnostic en phytoprotection (LEDP) for their help and advice throughout the writing of this book.

SOURCES

The contents of this guide are based on the first edition, as well as on information on the IRIIS Phytoprotection website: www.iriisphytoprotection.qc.ca

PHOTO CREDITS

Principal Photographer: Amélie Picard, LEDP, MAPAQ

In the coding used for the other photographers below, the number represents the page number where the image is found, and the letter corresponds to the one associated with the image in the species legend.

Other photographers:

Romain Néron, LEDP, MAPAQ : 38ABC, 39D, 44B, 50ABCD, 51EFGI, 52AD, 53EGI, 70B, 90C, 94AB, 113I 134AB, 140ABCD, 141EFG, 142C, 162ABC, 163DEF, 190A, 196A, 213G, 223I, 228A, 249E, 250AB, 256ABCD, 257EFG, 258AB, 259EF, 262A, 264B, 265EFH, 270A, 272ABCD, 273EFG, 274A, 275E, 276A, 279E, 280AB, 281E, 282AB, 283E, 284AB, 285E, 286AB, 287E, 288ABC, 289D, 290ABCD, 291EFG, 292ABCD, 293EFG, 294AB, 296A, 297EG, 298A, 299D, 308ABC, 309ABC, 310ABC, 311ABC, 315AB

Bernard Drouin, LEDP, MAPAQ : 246ABCD

Sam Brinker, Ontario’s Ministry of Northern Development, Mines, Natural Resources and Forestry: 254ABC

Sandra Flores-Mejia, CÉROM : 46A

vi Identification Guide to the Weeds of Quebec

Vincent Coulombe, LEDP MAPAQ : 29H, 31H, 33I, 37J, 39E, 41H, 43H, 45H, 47I, 51H, 53H, 55H, 57H, 59H, 61I, 63H, 65H, 67H, 69H, 71H, 73H, 75H, 77H, 79H, 81H, 83I, 85H, 87H, 89H, 91I, 93H, 95I, 97H, 99H, 101H, 103I, 105I, 107H, 109H, 111I, 113H, 115H, 117H, 119H, 121H, 123J, 125I, 127H, 129I, 131I, 133H, 135H, 137I, 139H, 141H, 143I, 145I, 147H, 149I, 151H, 155H, 157H, 159H, 163G, 165H, 167H, 169H, 173H, 175H, 177I, 179I, 181H, 183H, 184D 185FH, 187H, 189H, 191H, 193I, 195I, 197I, 199I, 201I, 203I, 207I, 209I, 211H, 213I, 215H, 217H, 219G, 221I, 223H, 225H, 227H, 233I, 235I, 247H, 249H,

251G, 253H, 257H, 259H, 261H, 263H, 267I, 269H, 271H, 273H, 275H, 277I, 279H, 281H, 283H, 285H, 287H, 289G, 291H, 293H, 295H, 297H, 299G

vii Preface v Acknowledgements .......................................................................................... v Sources v Photo credits v Introduction........................................................................................................ 1 Integrated Pest Management 4 Weed resistance to herbicides......................................................................... 5 Morphology of Dicotyledons 7 Identification key for Dicotyledons 12 Module 1 : Seedlings with orbicular cotyledons ................................... 13 Module 2 : Seedlings with oblong cotyledons 14 Module 3 : Seedlings with elongated cotyledons ................................. 16 Module 4 : Seedlings with linear and unusually shaped cotyledons... 18 Module 5 : Young plants with rosette and alternate leaves 19 Module 6 : Young plants with opposite leaves arranged in a rosette 22 Module 7 : Young plants with alternate leaves on a stem .................... 23 Module 8 : Young plants with opposite leaves on a stem .................... 25 Dicotyledons 27 Amaranthaceae ....................................................................................... 28 Redroot amaranth 28 Powell’s amaranth ............................................................................. 30 Waterhemp ........................................................................................ 32 Palmer’s amaranth 34 Spear saltbush ................................................................................... 36 Creeping saltbush 38 Fig-leaved goosefoot 40 Common lamb’s-quarters ................................................................. 42 Oak-leaved goosefoot 44 Kochia ................................................................................................ 46 Anacardiaceae 48 Poison ivy 48 Apiaceae (Umbelliferae) ........................................................................ 50 Meadow cow parsnip 50 Giant hogweed ................................................................................. 52 Wild carrot ......................................................................................... 54 Wild parsnip 56 Apocynaceae .......................................................................................... 58 Common milkweed 58 Asteraceae (Compositae) ....................................................................... 60 Common yarrow ............................................................................... 60 Biennial wormwood 62 Common wormwood ........................................................................ 64 Nodding beggarticks 66

contents

Table of

viii Identification Guide to the Weeds of Quebec Canada thistle 68 Bull thistle ........................................................................................... 70 Wild chicory 72 Orange hawkweed 74 Hairy galinsoga .................................................................................76 Low cudweed 78 Great burdock ................................................................................... 80 Common burdock 82 Great ragweed 84 Common ragweed ............................................................................ 86 Field sow-thistle 88 Common sow-thistle .......................................................................... 90 Prickly sow-thistle .............................................................................. 92 Prickly lettuce 94 Rough cockleburr .............................................................................. 96 Autumn hawkbit 98 Oxeye daisy .................................................................................... 100 Scentless chamomile ....................................................................... 102 Pineappleweed 104 Common dandelion ........................................................................ 106 Meadow goatsbeard 108 Sticky ragwort................................................................................... 110 Common ragwort ............................................................................. 112 Common tansy 114 Coltsfoot ............................................................................................ 116 Grass-leaved goldenrod 118 Canada goldenrod 120 Canada horseweed .........................................................................122 Balsaminaceae 124 Purple jewelweed .............................................................................124 Brassicaceae (Cruciferae) 126 Bitter wintercress 126 Common shepherd’s purse ..............................................................128 Common peppergrass 130 Corn mustard ....................................................................................132 Field mustard ....................................................................................134 Wild radish 136 Marsh yellowcress .......................................................................... 138 Creeping yellowcress 140 Field pennycress .............................................................................. 142 Wormseed wallflower .................................................................... 144 Caryophyllaceae 146 Common mouse-ear chickweed .................................................... 146 White campion 148

ix Table of contents Bladder campion 150 Night-flowering catchfly ................................................................. 152 Corn spurry 154 Grass-leaved starwort 156 Common chickweed ....................................................................... 158 Convolvulaceae 160 Dodders ........................................................................................... 160 Field bindweed 162 Hedge bindweed 164 Euphorbiaceae ...................................................................................... 166 Sun spurge 166 Common three-seeded mercury .................................................... 168 Fabaceae (Legumes) ............................................................................. 170 Black medick 170 Tufted vetch ...................................................................................... 172 Geraniaceae 174 Common storksbill ............................................................................ 174 Hypericaceae .........................................................................................176 Common St. John’s-wort 176 Lamiaceae (Labiatae)............................................................................ 178 Common hemp-nettle 178 Lythraceae .............................................................................................. 180 Purple loosestrife ............................................................................. 180 Malvaceae 182 Velvetleaf ......................................................................................... 182 Common mallow 184 Onagraceae 186 Common evening-primrose (Yellow evening-primrose) ............... 186 Oxalidaceae 188 European wood-sorrel .................................................................... 188 Plantaginaceae 190 Butter-and-eggs 190 Common plantain............................................................................ 192 Polygonaceae 194 Curled dock ..................................................................................... 194 Sheep sorrel ..................................................................................... 196 Pale smartweed 198 Leathery knotweed.......................................................................... 200 Prostrate knotweed 202 Japanese knotweed ........................................................................ 204 Eurasian black bindweed ............................................................... 206 Spotted lady’s-thumb 208 Marshpepper smartweed ................................................................ 210

x Identification Guide to the Weeds of Quebec Portulacaceae 212 Common purslane ............................................................................ 212 Ranunculaceae 214 Common buttercup 214 Creeping buttercup .......................................................................... 216 Rosaceae 218 Silverweed ........................................................................................ 218 Rough cinquefoil 220 Sulphur cinquefoil 222 Rubiaceae .............................................................................................. 224 Smooth bedstraw 224 Scrophulariaceae .................................................................................. 226 Common mullein ............................................................................. 226 Solanaceae 228 Hairy nightshade ............................................................................. 228 Eastern black nightshade 230 Jimsonweed ..................................................................................... 232 Violaceae ............................................................................................... 234 European field pansy 234 Morphology of the Poaceae (grasses) ...................................................... 236 Identification key for Poaceae (grasses) 242 Module 9 : Strictly annual species ....................................................... 243 Module 10 : Perennial or short-lived perennial species ..................... 244 Monocotyledons 245 Cyperaceae ........................................................................................... 246 Yellow nutsedge 246 Annual Poaceae (grasses) 248 Smooth crabgrass ........................................................................... 248 Hairy crabgrass 250 Large barnyard grass ...................................................................... 252 Jointed goatgrass 254 Woolly cupgrass 256 Common wild oats .......................................................................... 258 Common panicgrass 260 Fall panicgrass ................................................................................. 262 Proso millet ....................................................................................... 264 Giant foxtail 266 Yellow foxtail ................................................................................... 268 Green foxtail 270 Perennial Poaceae (grasses) ................................................................. 272 Redtop .............................................................................................. 272 Reed canarygrass 274 Smooth brome ................................................................................. 276

xi Table of contents Quackgrass 278 Orchard grass.................................................................................. 280 Red fescue 282 Common timothy 284 Annual ryegrass .............................................................................. 286 Perennial ryegrass 288 Rice cutgrass .................................................................................... 290 Leafy muhly 292 Foxtail barley 294 Annual bluegrass............................................................................. 296 Kentucky bluegrass 298 Common reed .................................................................................. 300 Pteridophytes ................................................................................................ 303 Equisetaceae 304 Field horsetail................................................................................... 304 Cultivated species 307 Grains ..................................................................................................... 308 Cultivated oats ................................................................................. 308 Common wheat 309 Common barley ............................................................................... 310 Common rye 311 Clovers and alfalfa ................................................................................. 312 White clover...................................................................................... 312 Alsike clover 313 Red clover ......................................................................................... 314 Alfalfa 315 Rapeseed 316 Common buckwheat............................................................................... 317 Appendices 318 Seedlings with orbicular cotyledons ..................................................... 318 Seedlings with oblong cotyledons 320 Seedlings with elongated cotyledons 323 Seedlings with linear and unusually shaped cotyledons.................... 325 Glossary 327 Index .......................................................................................................... 333

The Identification Guide to the Weeds of Quebec is an illustrated guide that aims to facilitate the visual identification of weeds. This pocket guide is ideal for field identification, as it covers many of the species likely to be found in or near an agricultural field. The description of each species is always accompanied by several photos.

The weeds included here are divided into three major groups: Dicotyledons (broadleaf weeds), Monocotyledons (Poaceae and Cyperaceae), and Pteridophytes. At the end of the Guide, a companion section briefly describes the characteristics of some crop species that may appear as weeds in an agricultural field.

The additional sections thereafter briefly supplement the information provided in the plant species entries.

Integrated pest management and weed resistance to herbicides

The Guide’s coaching and support role also extends to two sections on integrated pest management (IPM) and weed resistance to herbicides. IPM and herbicide-resistance interventions both begin by identifying and understanding the weeds in the field.

Morphology of Dicotyledons and Poaceae

The sections on the morphology of Dicotyledons and Poaceae describe the various form plants grow in and illustrate the various botanical terms used to describe these forms. These sections support the identification keys.

Identification keys

Two identification keys are provided: the first helps users identify Dicotyledons (broadleaves) and the second, Poaceae. The identification keys are designed according to the growth stage of the plant and help identify the species in most cases. Not included in these keys are cultivated species, Cyperaceae, or Pteridophytes.

Plant species entries

Each species in the Guide is presented in an entry, which is divided into four sections: title, botanical description, similar species, and pictures.

The title is made up of the accepted English, French, and Latin names, as well as other common names. European and Mediterranean Plant Protection Organization (EPPO) codes have been added. These are a quick and easy way to refer to a weed without having to write out its full name. Each code is

Introduction

unique and specific to a species. In addition, information is provided on the life cycle of the plant (annual, biennial, and perennial) as well as its origin (native to Quebec or introduced). Four logos can be found in the Guide. They were developed to indicate certain plant characteristics:

Invasive exotic: Species that have been introduced voluntarily or accidentally to Quebec, and that quickly and densely colonize new sites.

Toxic: Species that should not be touched since they can cause severe skin irritation.

Allergenic: Species the pollen of which may cause hay fever or severe seasonal allergic rhinitis.

Regulated: Species that are a nuisance and are regulated under Canadian and Quebec laws and regulations.

The botanical description presents the main morphological characteristics of each species according to its stages of growth. Thus, seedling characteristics are described first, followed by characteristics during the vegetative, inflorescence, and infrutescence stages.

The similar species section is new in the plant entries. It indicates which species may be confused with the entry species, and specifies what characteristics to observe to confirm the identification. Pictures sometimes accompany this section.

Pictures illustrate the species’ main characteristics, emphasizing the distinguishing traits. Thus, images of the seedling, vegetative, and inflorescence stages are presented. A line is displayed on some pictures for scale to help users better visualize the size of the specimens and their various organs. The horizontal line is one centimetre and the vertical line, one millimetre

2 Identification Guide to the Weeds of Quebec

Appendices

Because it can be difficult to differentiate between Dicotyledon plants at the seedling stage, the appendices gather photos of these broadleaf seedlings according to the shape of their cotyledons. Seedlings with orbicular cotyledons are presented together, as are the oblong, elongated, linear, and unusually shaped cotyledons.

Glossary

A glossary is provided at the end of the Guide. It defines most of the botanical terms used herein.

3 Introduction

Integrated Pest Management

Integrated Pest Management (IPM) is a decision-making approach to promote sustainable agri-environmental practices in pest management, with the ultimate goal of limiting pesticide use.

This method is divided into five components:

1. Knowing the enemies (i.e. the main weeds, their life cycle, and the different methods to control them);

2. Preventive methods (implementation of biosecurity measures, site selection, cultivar selection, and fertilizer and irrigation management);

3. Field monitoring (scouting and sampling for weeds);

4. Intervention (mechanical, biological, and chemical means, used in combination); and,

5. Feedback on the effectiveness of phytosanitary treatments, which leads to better planning for the next growing season.

This guide will help you to identify weeds in the field, gain better knowledge of these species, and monitor them rigorously via scouting, all of which are essential to integrated pest management.

Properly documenting problem species in the field, by correctly identifying weeds, also improves the management of a crop field. Weeds provide essential agronomic information, such as soil condition, that helps in planning rotations, tillage, and control methods. Weeds can also provide information on the effectiveness of a herbicide treatment.

4 Identification Guide to the Weeds of Quebec

Weed resistance to herbicides

This guide is a valuable tool for applying the principles of Integrated Pest Management (IPM), which are making a significant contribution to slowing the growing and widespread phenomenon of herbicide resistance.

Weed resistance to herbicides is the significant decrease in the susceptibility of a weed population to one or more herbicides that were previously effective in controlling it under normal conditions of use.

Some weeds are naturally resistant to different families of products. The repeated use of the same product selects the individuals that are naturally resistant to that family of products and therefore will be the only ones to reproduce. Few at first, the number of resistant individuals becomes greater and greater. That’s why resistance intensifies with each passing season.

In the field, when a herbicide treatment shows little effectiveness at eliminating or even controlling a weed species, certain factors during the application of the herbicide are potentially at fault and should be checked. For example, the application may have been made at the wrong growth stage of the weed; weather conditions may have been unfavourable at the time of application; an error may have been made in the dosage; or, a product was used that is not approved for the weed being treated. However, if these factors were taken into account when the herbicide was applied and weeds persist after treatment, these weeds may be resistant to the product used.

Certain characteristics strengthen the hypothesis of herbicide resistance. For example, only one weed species survived the treatment and its distribution pattern is random; in this weed population, the level of herbicide injury varies from plant to plant; persistence of weed population(s) after treatment has been observed in recent years in this field with the use of herbicides from the same group; herbicides from the same group have been used repeatedly, year after year in this field; resistance has been observed in this weed in Quebec.

An integrated weed management strategy must be implemented at all times to address resistance, regardless of whether or not resistance has been observed. Resistance detection is also a fundamental tool for establishing an optimal management strategy for resistant populations.

This guide does not mention the species in which resistance has been found, as new populations of resistant weeds and resistance to new herbicide groups are constantly being discovered. The list of resistant weeds in Quebec is updated annually by the LEDP weed science team and is easily accessible on the Internet.

6 Identification Guide to the Weeds of Quebec

Morphology of Dicotyledons (Broadleaf weeds)

1. Seedling characteristics

A seedling necessarily comes from a seed. The growth of the seedling begins with the emergence of the cotyledons, which are the first organs to appear on the soil surface. Initially, only a white thread is visible, often accompanied by the seed coat. The latter falls off once the cotyledons have fully extended. Tufted vetch is an exception, as its cotyledons remain underground, in the seed.

The seedling consists of the stem (the part of the seedling axis that is above the cotyledon attachment point) and the hypocotyl (the part below the cotyledon attachment point). The new leaves appear at the top of the seedling’s growth axis. The leafy shoots come from the buds in the leaf axils.

seed ﬁlament seed coat

emergence

leaves leaf

shoot

roots

Seedling

new

steem leafy

cotyledon hypocotyl

Parts of the seedling

In some species, the stem elongates very early in the seedling’s development. In others, it does not develop or develops very little. In the first case, the seedlings are stemmed; in the second, they are rosetted.

The first leaves can be alternate or opposite. One way to confirm the arrangement of leaves on the seedling is to check if new leaves appear one after the other (alternate) or both at the same time (opposite).

Often, the first leaves show juvenile characteristics, with the definitive species traits not showing until the later leaves.

8 Identification Guide to the Weeds of Quebec

Stemmed seedling Rosetted seedling Alternate-leaf seedling Opposite-leaf seedling

Cotyledon shape

Common forms

check the length/width (l/w) ratio of the blade

orbicular: the length is equal to the width

oblong: the length is between 1 and 3 times the width

elongated: the length is between 3 and 8 times the width orbicular-

linear: the length is more than 8 times the width

Remarkable shapes

9 Morphology of Dicotyledons

diamond square

auricular heart spade

2. Vegetative plant characteristics

A vegetative shoot is a young plant that grows from the germination of a bud located on a vegetative part (rhizome, stolon, or tuber).

Leaf characteristics

Leaf morphological groups

leaves with entire margins

leaves with dentate (or sinuous and serrated) margins

leaves with deeply divided margins (segments, lobes) and compound leaves (with distinct leaflets)

10 Identification Guide to the Weeds of Quebec

Leaf shapes

rounded to oval: the length is less than 2 times the width

elongated: the length is between 2 and 8 times the width

linear: the length is more than 8 times the width

11 Morphology of Dicotyledons

the length/width (L/w) ratio of the blade

Check

Identification key for Dicotyledons

The identification key on the following pages is provided as a guide to facilitate the identification of various species. Common plant characteristics were taken into account when classifying weeds, including the cotyledon, leaf, and blade margins. However, these criteria may change depending on the environment in which the weed is growing. Consulting specialists is still the best avenue for proper weed identification.

Developmental stages of the plant

5 leaves or fewer

• Seedling

Orbicular cotyledons: Module 1

Oblong cotyledons: Module 2

Elongated cotyledons: Module 3

Linear and unusually shaped cotyledons: Module 4

• Vegetative growth (from an underground structure): Refer to the 6-leaf or more stage

6 leaves or more

• Young rosetted plants

Alternate leaves: Module 5

Opposite leaves: Module 6

• Young stemmed plants

Alternate leaves: Module 7

Opposite leaves: Module 8

12 Identification Guide to the Weeds of Quebec

13 Identification key for Dicotyledons

Seedlings with orbicular cotyledons 1st and

leaves

4th and 5th leaves Blade margin Shape Blade margin Shape Seedling type Species Page Entire or almost entire Rounded to oval Entire Rounded to oval Rosette with alternate leaves Bitter wintercress 126 Rosette with alternate leaves (first and second leaves are opposite) Common mullein 226 Field pennycress 142 Dentate Rounded to oval Rosette with alternate leaves Marsh yellowcress 138 Dentate Rounded to oval Dentate Rounded to oval Stem with opposite leaves Hairy galinsoga 76 Common hemp-nettle 178 Stem with alternate leaves, first and second leaves are opposite Common threeseeded mercury 168 Rosette with alternate leaves European field pansy 234 Elongated Rosette with alternate leaves Field sow-thistle 88 Common sow-thistle 90 Prickly sow-thistle 92 Prickly lettuce 94 Common dandelion 106 Deeply divided Rounded to oval Rosette with alternate leaves Rough cinquefoil 220 Sulphur cinquefoil 222 Common wormwood 64 Rounded or oval, heart-shaped base Dentate Rounded or oval, heart-shaped base Stem with alternate leaves Velvetleaf 182 Elongated Dentate Elongated Opposite stem and leaves Purple jewelweed 124 Deeply divided, fine segments Elongated Rosette with alternate leaves (first and second leaves are opposite) Pineappleweed 104 Deeply divided Rounded to oval Deeply divided Rounded to oval Stem with opposite leaves Common ragweed 86 Deeply divided, fine segments Elongated Deeply divided, fine segments Elongated Rosette with alternate leaves (first and second leaves are opposite) Scentless chamomile 102

Module 1:

2nd

3rd,

Module 2: Seedlings with oblong

3rd,

1st and 2nd

14 Identification Guide to the Weeds of Quebec

cotyledons

leaves

4th, and

leaves Blade margin Shape Blade margin Shape Seedling type Species Page Entire or almost entire Rounded to oval Entire or almost entire Rounded to oval Rosette with opposite leaves White campion 148 Night-flowering catchfly 152 Bladder campion 150 Rosette with alternate leaves Common plantain 192 Canada horseweed 122 Stem with opposite leaves Common mouse-ear chickweed 146 Common St. John’s-wort 176 Rounded or oval, heart-shaped base Rosette with alternate leaves Common burdock 82 Great burdock 80 Elongated Stem with opposite leaves Purple loosestrife 180 Stem with alternate leaves Marshpepper smartweed 210 Rosette with alternate leaves Grass-leaved goldenrod 118 Common evening-primrose 186 Rosette with alternate leaves, first and second leaves are opposite Wormseed wallflower 144 Rounded or oval, 2 lobes at the base Rosette with alternate leaves Sheep sorrel 196 Dentate Rounded to oval Rosette with alternate leaves Canada goldenrod 120 Rounded or oval, heart-shaped base Rosette with alternate leaves Coltsfoot 116 Elongated Rosette with alternate leaves, first and second leaves are opposite Common shepherd’s purse 128 Composed of 3 leaflets Rounded to oval Rosette with alternate leaves Black medick 170

5th

E: stem; F: leaf; G: whole plant; H: seeds.

Similar species

Powell’s amaranth (p. 30) can be distinguished in the vegetative stage by its less pubescent, almost glabrous stem, and its green, slightly shiny, more lanceolate leaves. When blooming, it can be distinguished by its longer inflorescence.

Hairy nightshade (p. 228) can be distinguished in its vegetative stage by its tip-terminated leaves. When blooming, hairy nightshade produces clusters of small white flowers.

29 Dicotyledons

Redroot amaranth

G E F H

Powell’s amaranth

Syn. Green pigweed

Amarante de Powell

Amaranthus powellii S. Wats. AMAPO

Annual species, introduced

Botanical description

A: two-leaf seedling;

B: five-leaf seedling;

C: vegetative plant;

D: mucro at the apex of the leaf blade.

The seedling has a stem and alternate leaves. The cotyledons are elongated, and the first leaves are rounded to oval, with an entire margin. The undersides of the cotyledons and first leaves are often a purple-red colour. The root system is made up of a shallow taproot. The vegetative plant has an upright stem that is slightly pubescent or almost glabrous and 20 to 150 cm high. The mature leaves, which alternate on the stem, are entiremargined, rounded to oval in shape, and slightly shiny, with a retuse apex and a mucro. The inflorescence is a dense panicle composed of elongated, compact spikes made up of the male and female flowers (monoecious species). Each flower is surrounded by sharp-pointed bracts that are 7 to 10 mm long and give the inflorescences a prickly appearance. The fruit is a dehiscent utricle that opens along a transverse line. It contains a single, very small (1 mm), dark brown and shiny seed.

30 Identification Guide to the Weeds of Quebec

Amaranthaceae

A B C D

This second edition of the Identification Guide to the Weeds of Quebec is the ideal field tool for visually identifying weeds, from seedling to mature stage.

It presents 133 weed species and 10 cultivated species that may be observed as weeds in agricultural fields.

The updated images, texts, and identification keys modernize this guide and make it a useful tool to take with you on your field visits.

PEDI0221-PDF