Identification guide to the weeds of Quebec

Index to Families by Colour ,, "· ,.,

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Amaranthaceae (Amaranth Family) .......... 18 Asclepiadaceae (Milkweed Family) .......... 22 Caryophyllaceae (Pink Family) ............... 24 Chenopodiaceae (Goosefoot Family) ........ 36 Compositae (Aster Family) .................. 42 Convolvulaceae (Morningglory Family) ....... 86 Cruciferae (Mustard Family) ................. 88 Euphorbiaceae (Spurge Family) ............. 106 Labiatae (Mint Family) ..................... 110 Leguminosae (Legume or Bean Family) ...... 112 Malvaceae (Mallow Family) ................ 114 Onagraceae (Eveningprimrose Family) .......116 Oxalidaceae (Woodsorrel Family) ............118 Plantaginaceae (Plantain Family) ............120 Polygonaceae (Smartweed Family) ..........122 Portulacaceae (Purslane Family) .............138 Ranunculaceae (Buttercup Family) ..........140 Rosa�eae (Rose Family) ....................142 Scrophulariaceae (Figwort Family) ...........144 Solanaceae (Nightshade Family) ............146 Umbelliferae (Carrot Family) ................150 Cyperaceae (Sedge Family) ................ 154 Gramineae (Grass Family-annual species) .... 156 Gramineae (Grass Family-perennial species) . 177 Equisetaceae (Horsetail Family) ............. 206 Others ................................... 209

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Identification Guide to the

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ByCLAUDEJ.BOUCHARD and ROMAIN NÉRON with the collaboration of LOUISE GUAY

Centre ARICO/Systèmes experts en phytoprotection Direction des services technologiques

MAPAQ

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Edited by the Conseil des productions végétales du Québec inc.

DII Québec aa

The concept for this publication originated with Claude J. Bouchard and Romain Néron, and was carried out by them with the collaboration of Louise Guay, all three of whom work for the Direction des services tech­ nologiques du ministère de !'Agriculture, des Pêcheries et de !'Alimen­ tation du Québec (MAPAQ).

Centre ARICO brings together the resources of the Direction des ser­ vices technologiques to provide decision-making systems related to crop protection.

Publisher: Conseil des productions végétales du Québec inc. (CPVQ) 200, chemin Sainte-Foy, 1" étage Québec (Québec) G1R 4X6 Telephone: (418) 646-5766 Fax: (418) 646-1830 and 644-5944 E-mail: cpvq@cpvq.qc.ca Custorner Service: (41 B) 523-5411 or 1 888 535-2537 (toll-free number) Distributor: Distribution de livres Univers Telephone: ( 418) 831-7474 or 1 800 859-7474 E-mail: d.univers@videotron.ca

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This publication is also available in French under the title "Guide d'identification des mauvaises herbes du Québec" (ISBN 2-89457-162-3)

PRINTED IN QUEBEC LEGAL DEPOSIT -1999 BIBLIOTHÈQUE NATIONALE DU QUÉBEC, 1999 BIBLIOTHÈQUE NATIONALE DU CANADA, 1999 ISBN 2-89457 -174-7 © MAPAQ-Gouvernement du Québec

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Foreword This identification guide follows on two previous projects: the Atlas des mauvaises herbes and the SlPO software for identifying weed seedlings.

The Atlas was published in the form of richly illustrated pamphlets comparing groups of species that resemble each other at the seedling stage. Their purpose was to fill a gap in the understanding of weed development at the young plant stage, and also to point out the dis­ tinctive characteristics of each species at the seedling, vegetative, and mature stages. More than 40 species were covered by the Atlas.

The SIPO* software, presently in version 2.0, uses the resources of arti­ ficial intelligence to transfer expertise in seedling identification. lt is an expert system, and the results are accompanied by a coefficient that measures the degree of confidence for a given species identification. The coefficient can also be used for measuring the distance separating the identified species and similar-looking species. SIPO contains about 150 species at the seedling stage.

The ultimate objective of these projects is always to better understand the flora of cultivated fields. This new publication contributes particularly to this goal by offering, in a practical format, an overall portrait of each of the 120 species described. Close to 650 colour photos are integrated with the plant descriptions.

Acknowledgements We wish to thank the agrologists, technologists, and others who tested out the preliminary version of the guide and provided their comments and suggestions. We would particularly like to thank Pierre Lachance, regional consultant in crop protection with Montérégie East, and his col­ laborators who helped by raising important questions and by affirming the contents of this guide.

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Photo Credits The photographs corne from documentation on weeds which is main­ tained at the Herbier du Québec. The grasses and many of the dicotyle­ dons were recently photographed by the authors, and others were pho­ tographed at various times by Mr. Bernard Drouin.

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SIPO (Système d'identification des plantules de mauvaises herbes par ordi­ nateur) was designed by the authors in close collaboration with computer sci­ entists Pierre Plante and André Plante at the Centre ATO of UQAM.

SIPO is one of three expert systems (SIPO, DESHERB and HORPERT) included in ARICO software.

For more information: http://www.agr.gouv.qc.ca/dgpar/arico

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Table of Contents Foreword ....•............... v Acknowledgements ..•..••..... v Photo Credits •••.•. , •.•...•.• vl Introduction .....•.•.•...•.•. , 1 How to Use this Guide .•.•.•.... 3 Tips for Getting the Right Identification ...•..•.•••.. 6 Morphology of the Dicots ..••..•. 8 Morphology of the Grasses ...•. 12 DICOTS

(Broadleaf species) .......... 17

Amaranthaceae (Amarant11 Family) 18 Redroot pigweed ....•.••..•• 18 Green pigweed •••••......•.. 20 Asclepiadaceae (Milkweed Family) 22 Common milkweed ••••...... 22 Caryophyllaceae (Pink Family) •... 24 Mouse-eared chickweed •••... 24 White cockle ............•... 26 Bladder campion •....•..••.. 28 Night-flowering catchfly ....... 29 Corn spurry ......••.......• 30 Grass-leaved stitchwort •••••.. 32 Ch�kweed ..••••••••••..... 34 Chenopodiaceae (Goosefoot Family) ....•.••••.. 36 Spreading atriplex ••.......•• 36 Halberd-leaved atriplex ....... 37 Lamb's-quarters .....••...... 38 Oak-leaved goosefoot •....... 40 Compositae (Aster Family) .•.... 42 Yarrow •......••••......... 42 Mugwort •......•••••.•...•• 44 Nodding beggarticks ••••••••. 45 Canada thistle .........••••• 46 Bull thistle .•••...•..••.••... 48 Hairy galinsoga •••.••..••...• 50 Low cudweed •••..•••...•.•. 52 Perennial sow-thistle .•••....• 54 Smooth perennial sow-t11istle ... 55 Annual sow-thistle ....•....•. 56 Spiny annual sow-thistle ••.... 58 Prickly lettuce ........••..... 60 Cocklebur ..............••.. 62 Ox-eye daisy ..•. , .......•.. 64

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Scentless chamomile ...••..•. 66 Stinking mayweed ...••••.... 67 Pineappleweed .......•••••.. 68 Common burdock ..•••••.•.. 70 Great burdock •......•.••••• 71 Common ragweed ..••.•••••• 72 Dandelion .••••••.......•••• 74 Meadow goat's-beard •..•.••• 76 Common groundsel •••......• 78 Colt's-foot .....•••••••••..•• 80 Canada goldenrod ••..•••.•.. 82 Narrow-leaved goldenrod •••... 83 Canada fleabane ...••••••..• 84 Convolvulaceae (Morningglory Family) .......... 86 Hedge bindweed .....•. , .•.. 86 Field bindweed .............. 87 Cruciferae (Mustard Family) , .... 88 Yellow rocket •......... , , , , , 88 Shepherd's-purse ......... , , . 90 Common pepper-grass ..... , . 92 Wild mustard ....... .. 94 Bird rape .•..... , , , , , ....•• , 96 Wild radish ......... , .. , .... 98 Marsh yellow cress ..... , , ... 1 00 Creeping yellow cress ....... 101 Stinkweed •••••..••••....,, 102 Wormseed mustard ••....... 104 Euphorbiaceae (Spurge Family) .. 106 Sun spurge ........••••.... 106 Three-seeded mercury ..••... 1 08 Labiatae (Mint Family) ......••. 11 o Hemp-nettle .•.........•••. 11 o Leguminosae (Legume or Bean Family) •.....• 112 Tufted vetch ....•••••••...• 112 Malvaceae (Mallow Family) ..... 114 Velvetleaf .....•..••••••... 114 Onagraceae (Eveningprimrose Family) •..... 116 Yellow evening-primrose •••.. 116 Oxalidaceae (Woodsorrel Family) 118 European wood-sorrel .•••..• 118 Plantaginaceae (Plantain Family) . 120 Broad-leaved plantain ...••.. 120 Polygonaceae (Smartweed Family) ••......... 122 Curled dock ............... 122

Table of Contents (contlnued) Sheep sorrel •••............124 Prostrate knotweed •••...... 126 Striate knotweed • , • , .......127 Wild buckwheat ... , .••••...128 Lady's-thumb ........•..••.130 Marshpepper smartweed ••••.132 Green smartweed ..........•134 Buckwheat ................•136 Portulacaceae (Purslane Family) •138 Purslane .•••........••....138 Ranunculaceae (Buttercup Family) ..... , •••.•.140 Creeping buttercup ......••• 140 Tall buttercup .••.........••141 Rosaceae (Rose Family) .•..... 142 Rough cinquefoil •..........142 Sulphur cinquefoil ...••.....•143 Scrophulariaceae (Figwort Family) ..............144 ..... 144 Yellow toadflax . , . , .

Solanaceae (Nightshade Family) .146 Eastern black nightshade .•••. 146 Black nightshade .....•..... 147 Hairy nightshade ...... , ..• , 148 Umbelliferae (Carroi Family) ....150 Wild carrot ..............•• 150 MONOCOTS (Grasses and grass-like species) .... , , i 53 Cyperaceae (Sedge Family) ..... 154 Yellow nut sedge .....•..... 154 Gramineae (Grass Family-annual species) .. 156 Smooth crab grass .......... 156 Large crab grass ............ 158 Barnyard grass ••...... , , ... 160 Wild oats ......••••........ 162 Witch grass ............... , 164 Fall panicum .•.•........... 166 Fall panicum (typical) •....... 167 Proso millet .........•••.... 168 Giant foxtail ............... 170 Yellow foxtail ........•.•.••• 172 Green foxtail ..••........••• 174 Bristly foxtail ...•••........• 176 Gramineae (Grass Famlly-perennial specles) 177 Redtop ...................178 Reed canary grass .......... 180

Smooth brome ...•..•••••..182 Quack grass .........•.•••. 184 Orchard grass .....•••••.•••186 Red fescue ...••.••.......• 188 Timothy .......•..........•190 ltalian rye grass ••... , •••••.192 Perennial rye grass ..........194 Rice eut grass ........•••... 196 Wire-stemmed muhly .•......197 Annual blue grass .....••••..198 Kentucky blue grass ...•••••.200 Common reed .........••••.202 PTERIDOPHYTES (Nonflowering plants) ....... , 205 Equisetaceae (Horsetail Family) .206 Field horsetall ....•.•......•206 OTHERS ..................209 CereaJ crops ................210 Oats ..................... 210 Wheat .................... 210 Barley ....................211 Rye ......................211 Clovers and Alfalfa •.•...•....212 White clover .......•.......212 Alsike clover ..•...•••.•....212 Red clover ................213 Alfalfa ......•........••••.213 Poison-ivy ..•....•••...•••••214 Panoramic Key ....•........• 217 Module1 ..•..•..•••......218 Module2 ..... , , .••••.....220 Module3 .•.........•••...223 Module4 ....•... , ...•••••225 Module5 .................226 Module6 ......•..•.......230 Module7 ......•..........231 Module8 ........... , , •..•233 Module9 ........••••.....234 Module 1 O .••••...••••••••235 Mosaic Key ... , , , ...••••.•••236 Glossary ........ , , , . , , ..••••244 Index of English Names ........248 Index of Latin Names .........250 Index of French Names ........ 252

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Introduction "A small, pocket-sized, illustrated book that can be used in the field to help recognize weeds." This is the wish of many people who are involved in crop production during the growing season. lt was to fulfill this wish that we prepared the guide that you now hold in your hand. Our main goal was to make lt easier to reoognize weeds in the field by providing sufflciently detailed descriptions, wlth the support of good photographie documentation. The lllustrated pages dealing with the morphology of plants and the vlsual keys are ail provîded ln order to help users in observlng speéimens and to quickly direct them towards the appropriate plant descriptions.

Most of the species dealt wlth are weeds that are frequent ln large-scale farming, whereas others are weeds found in fields as rernnants from pre­ vious crops (for example, spontaneously regenerating cereais) or plants that are especially abundant around the edges of fields, but should stilf be recognized (for example, Reed canary grass).

Each species is described separately, the description usually consisting of two facing pages in the guide. The tille of each description is the name of the plant in English, followed by the French and Latin names as recognized by the Weed Expert Committee (a popular name is some­ times added lo the English or French name; for Latin names, the sym­ bol = designates a synonym by which the species is known in botanical nomenclature); the species is also designated as either an annual, biennial, or perennial.

The plant description itself starts with the seedlihg or vegetatlve shoot stage (for example, ln perennial grasses, young plants originating from seed are rare and the seedling is not usually descrlbed}, followed by the mature stage (sometlmes a vegetatlve stage is also described).

Seedlings have few erg ans, but some of tl,em provide useful lndlcators, such as the cotyledons and leaves of dicots, and the ligule and the seed (still attached to the roots ln the soli) of grasses. ln dicots, characters such as the presence or absence of the stem and position of the leaves (a!ternate or opposite) are very useful ln separating species.

For seedllngs and vegetative shoots of grasses, the most important characters are pubescence, presence of auricles (always absent in annual species), and vernation Oeaves folded or rolled lengthwise in the bud shoot).

We also take into account the tact that many species show juvenile ohar­ acteristics in the seedling and young stages that differ from their defin­ itive mature characteristics. Mature plants are dealt with in a less systematic fashion, but we always indicate the growth habit, height, type of inflorescence, and often details about the flowers (spikelets in the grasses).

Morphology of the Dicots

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(broadleaf species)

Seedling emergence A seedling cornes from the germination of a seed, whereas a young plant that arises from a bud situated on an underground part of the plant is a vegetative shoot.

ln the field, we recognize a seedling by noting that it has cotyledons.

These are the first organs to appear above ground. Before emergence, the seedling under the soil looks like a white thread topped by a seed coat (it will lose the seed coat when it reaches the soil surface).

N.B.: an exception to this is Tufted vetch, in which the cotyledons stay underground in the seed, like a grass.

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Parts of the seedling The cotyledons are sometimes referred to as false leaves.

The stem is the part of the growth axis situated above the cotyledons' point of attachment; the hypocotyl is the part below.

The new leaves appear at the apex of the seedling's growth axis. Leaf shoots arise from buds in the leaf axils.

new leaves leaf leaf shoot stem cotyledon hypocotyl

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Seedling with stem/Seedling with rosette ln some species, the stem elongates very early during seedling develop­ ment, with the result that it is quite conspicuous. ln contras!, the stem develops very little or not at ail in some other species.

Seedling with rosette

Seedling with stem

SeedUng wlth alternate leaves/Seedling with opposite leaves Tue objective of phyllotaxy is to descrlbe the positioning of leaves on the stem, but when the stem ls only slightly developed, it ls hard to see if the leaves are isolated or in pairs opposite each other at each node.

Another way to.assess the phyllotaxy is to check whether the new leaves are appearing one alter the other (alternate leaves) or Iwo at a tlme (opposite leaves).

Seedling with alternate leaves First leaves and mature leaves The first leaves often present juvenile characteristics and the definitive characteristics of the species only show up on later leaves. For example, the leaves of a Marsh yellow cress seedling (see illustration).

Seedling with opposite leaves

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Cotyledon shapes Common shapes Check the leogth-to-wldth (L/W) cstlo ot the blade

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Oblong: lenglh belween 1 lo 3 limes the width

Orbicular: lenglh equals widlh

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Linear: length over 8 limes the width

Unusual shapes

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Orbicular­ auriculale

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Spade

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Morphological leaf groups Leaves having entire margins

Leaf margins toothed, wavy, or wavy-toothed

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

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Leaf shapes Check the length-to-width (L/W) ratio of the leaf blade

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Elongated: length between 2 to 8 times the width

Linear: length over 8 times the width 11

Morphology of the Grasses Seedling emergence A seedling cornes from the germination of a seed, whereas a young plant that arises fr0m a bud situated on an underground part of the plant is a vegetative shoot. ln the field, the first organ to appear above ground is the coleoptile, a membranous organ shaped llke a long casing that contains the young plant. Before emergence, the seedling in the soi! looks llke a white thread attached to the seed it came from (one can collect the seed to identify the species).

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Parts of a grass seedling

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The coleoptile is a temporary organ that dries up quickly and disappears.

The leaf is made up of two parts: the leaf blade and the leaf sheath.

The sheaths are inserted one inside the other.

The tillers are leaf shoots that arise at the leaf axils; they originate from from buds located at the base of the plant.

New leaves are found at the apex of the seedling's growth axis.

Cross-section of the leaf sheath

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flattened cross-section

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Vernation .-' .

Bud shoots are present in very young grasses befomthey develop culms / (stems). Vernation 1s the arrange·····--·-· ment of the leaves in the bud shoot (rolled up or folded up), , which can be seen as the new , .!\ • ·' ·' leaves begin to emerge. vernation: rolled up vernation: folded up

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The collar zone in a grass leaf The collar separates the leaf blade and the leaf sheath.

The sheath can be either open or closed.

The auricles (an extension of the leaf blade) can be either present or absent.

The ligule is present in almost all species.

ligule (membranous)

Types of ligules Ligule membranous: whitish or transparent, entire or somewhat torn at the top.

Ligule ciliate: consists of a row of fine hairs that may be more or less joined together at their base.

N.B.: the ligule is absent in Barnyard grass, and there is just a shiny white mark in its place.

membranous ligule

ciliate ligule

white mark (ligule absent) 13

Tillering Tillering is a process of ramification. lt starts at the 4 th or 5'h leaf stage of the seedling. The first tiller appears in the 1" leaf axil; the tillers then succeed one another in the leaf axils, following the leaves' order of appearance. The primary tillers can put forth secondaty tillers, and these can also put forth tertiary tillers, and so on.

The capacity for tillering is a characteristic of the species, but it is also affected by environmental conditions.

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Bunch grasses These are clump-forming grasses that produce a large quantity of tillers.

They do not produce stolons or rhizomes (or if they do, they are very short).

Rhlzomatous or stoloniferous grasses (creeping grasses) These are grasses with underground stems: rhizomes (rootstocks) are more-or-less buried and stolons creep along the soil surface (there is really no other difference between a rhizome and a stolon). Rhizomes and stolons have nodes that give rise ta vegetative shoots; they cause the prollferation and expansion of the plant. Growth of tillers is generally reduced.

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Flowers and spikelets The flowers of grasses are much less showy than those of the dicots, but they are also perfect flowers with a pistil and stamens. Each flower is surrounded by 2 bracts (the lemma and palea} designed here as "floral pieces" (a).

The spikelet is the basic morphological unit of the grass Inflorescence. lt is formed from one or more flowers surrounded by 2 other bracts that strongly resemble the floral pieces: the glumes (b).

The rachilla (c) is a short axis that bears the flowers in the spikelet.

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Distinctive characteristics, depending on the species:

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flowers may be unisexual; the spikelet may contain sterile flowers; a spikelet may have only one glume; the glumes may more-or-less envelope all the flowers in the spikelet; - the floral pieces and glumes may have an awn at the tip or on the back.

Diagram of a spikelet with 4 flowers

Inflorescence The inflorescence of a grass terminates the stem or the branches. lt is made up of spikelets that are grouped together in various ways, but it can be reduced to two basic types: the spike and the panicle.

Spike: The inflorescence is formed from a single axis

(rachis), usually having nodes and articulations. The spikelets are attached directly to the axis without an intermediary stalk. There may be several spikelets at one node (as in Six-row barley) or just one (as in Wheat and Quack grass).

Panicle: A branched inflorescence, usually pyramid­ shaped; the branches are more-or-less numerous and may themselves be branched. The spikelets are attached to the branches by a short stalk; they are usually concentrated near the ends of the branches, but may also be found in clusters along the branches.

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