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Weed

ScienceMike Maddox

Horticulture Educator

Rock Co. UW-Extension

What is a Weed?

• When weeding, the best way to make sure you

are removing a weed and not a valuable plant is

to pull on it. If it comes out of the ground

easily, it is a valuable plant.

~Author Unknown

What is a Weed?

• Plant out of place

• Plant with undesirable characteristics

• Plant with undiscovered virtues

• Or something else…

• How is a ‘weed’ different

from an ‘invasive species’?

What is a Weed?

• They compete with desirable plants for:

– Sunlight

– Nutrients

– Space

• They harbor insects and diseases

• Aesthetics

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What is a Weed?

• Abundant seed production

• Seed dormancy

• Seed survival

• Vegetative reproductive strategies

• Lack of ornamental appeal

• Offensive odor

• Toxic or noxious

• Dormancy

– Flowers/vegetables• Breeding has removed dormancy

• Seeds become less valuable if dormancy exists

– Weeds

• Dormancy allows weeds to survive harsh environmental

conditions

• May have different levels of dormancy within same plant

• Seed Survival

– Flowers/Vegetables

• Several years under ideal storage conditions

– Weeds

• Documented survival after 100 yrs. of burial

• Survival is possible with some species after

composting

• Seed production

– Flowers/Vegetables – few seeds per plant

• Sweet corn, up to 1000

• Pumpkins, several hundred

• “Seedless” watermelon

– Weeds

• Common purslane, 1,000,000+

• Common lambsquarters, 100,000

• Vegetative reproduction

– Flowers/Vegetables

• Very few perennials – those that are very few spreading root systems (Kentucky bluegrass)

– Weeds

• Perennials with spreading vegetative structures

• Annuals when pulled stem re-roots

• Tillage can propagate

• Toxic / Noxious

– Noxious

• Weed by law

• Why?

– Toxic

• Hazardous to humans and/or domesticated

animals

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Types of Weeds

• Annual and perennial weeds

• Grass-like and broadleaf weeds

• Weeds and invasive plants

• Control of each may vary

• Annual weeds

– Completes life-cycle in one year

– Reproduces primarily from seeds

– Examples:

• Summer annuals: common lambsquarters, redroot pigweed, giant foxtail, velvetleaf

• Winter annuals: common chickweed, field pennycress, shepherd’s purse

• Biennials: wild carrot, prickly lettuce, bull thistle

• Perennial weeds

– Life-cycle continues for 2 or more years

– Vegetative and sexual reproduction

– Examples:

• dandelion, quackgrass, Canada thistle

Types of Weeds

• Grass-like weeds

– Monocotyledons

– Annual or perennial

Types of Weeds

• Broad-leaf weeds

– Dicotyledons

– Annual or perennial

Weed Control

• Integrated Pest Management

– Culturally

– Mechanically

– Chemically

• Must recognize plant life cycle

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• Cultural

– Optimize planting density and plant health

• Proper plant spacing

• Proper mowing height

– Mulch

• Minimize exposed soil surface

• Prevent weeds from germinating

• Smother weeds

• Mechanical

– Physical removal of plant

• Severing annual weeds at ground line

• Pulling perennial weeds

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• Judicious and appropriate use of herbicides

– Selective herbicides

– Non-selective herbicides

– Pre-emergent herbicides

– Post-emergent herbicides

– Foliar applications

– Soil applications

• Selective herbicides

– Distinguish between broadleaf and grass-like

weeds

• Non-selective herbicides

– Does not distinguish between plants

• Pre-emergent herbicides

– Prevents seeds germination

• Post-emergent herbicides

– Applied to actively growing plants

• Contact

– Kills only the applied tissue

• Systemic

– Translocated throughout plant

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• Foliar application

– Applied to the leaves (or actively growing

tissue)

• Soil applications

– Applied to the soil

• Pre-emergence, selective herbicides

– Must be applied to soil before germination

– Used to kill annual grass and broad-leaved

weeds seedlings as they germinate

– Work best if mixed into upper 1-2” of soil or

watered in.

– Will NOT kill emerged weeds

• Products: (pre-emergent, selective)

– Pendimethalin

– DCPA (Dacthal, Weed & Grass Preventer, and

many others)

– Trifluralin (Preen, Treflan, and many others)

– Dichlobenil (Casoron)

– Simizine (Princep)

– Oryzalin (Surflan)

– Siduron

• Post-emergence, selective herbicides

– Applied after weeds are up and growing

– Can present a problem by drifting onto non-

target plants

• Broad-leaved weed control products:

– 2,4-D (many brand names)

– MCPP (many brand names)

– Dicamba (Banvel and others)

– Combination formulas (Trimec)

• Grass weed control products:

– Fluazifop-butyl (Grass-B-Gone, Fusilade)

– Sethoxydim (Poast)

• Post-emergence, non-selective herbicides

– Applied after weeds are up and growing

– Are circulated within the plant, giving a better

chance of killing roots of perennial weeds

– Danger of drift to non-target plants

– Some root uptake is possible but herbicide

generally applied to foliage

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Weed Control

• Products; (post-emergence, non-selective)

– Glyphosate (Round-up, Kleenup, Killzall, and

many others)

– Triclpyr (Brush-B-Gon, Garlon)

Selecting a Herbicide

• Factors to consider

– Liquid or granular

– Timing

– Weather

– Formulation

• Liquid

– Easily applied to plant, good for spot-treating

– Drift may be an issue

– Read label for temperature requirements

• Granular

– Many times granule must stick to leaf to be effective

– Read label for temperature requirements

• Timing

– Plant life cycle

• Most susceptible at flower-stage or after first frost

• Early season application can reduce photosynthate

• Late season application can translocate to root

• Pre-emergence herbicides must be down before

germination begins

• Weather

– Low temperature - restrict absorption/translocation

– Warm to moderately high temperature - best

absorption/translocation

– Very high temp. - dries on surface prior to

absorption

– Best to spray on calm days to avoid drift from wind

• Formulations

– Esters

• Volatile

• Readily absorbed

• Use during cool temps or hard-to-kill weeds

• Salts (Amines)• Less volatile

• Use during hot temps

• Less smell

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• Labels

– Read label for usage restrictions and handling

regulations

– Look for precautionary labels on containers

– Keep all pesticides in original container and locked

up where children cannot get to them

– Do not eat, drink, or smoke while handling

pesticides

– Dispose of unused product as directed

Trade Name

Identifying Information

Mixing Instructions Contact info

Ingredient Statement

Identifying Information

First Aid

Safety Information

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Herbicide Injury

• Problems will arise

• Following the label will minimize

suprises

Grass Weed Identification

ligule

auricles

leaf blade

collar region

leaf sheath

Broadleaf Weed Identification

alternate leaves opposite

leaves

Broadleaf Weed Identification

Ochrea – thin paper-like

sheath surrounding stem

at leaf axilFound on:

Wild Buckwheat,

Pennsylvania Smartweed,

Ladysthumb Smartweed

Barnyardgrass

• Annual

• Leaf sheath &

blade hairless

• Flattened stem

• No ligule

Barnyardgrass

• Flattened stem

(cross-section)

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Yellow Foxtail

• Annual

• Long hairs on

upper leaf

surface near

base of leaf

blade

• Hairy ligule

Giant Foxtail

• Annual

• Larger seedheads

that tend to

droop

• Upper leaf surface

with short bristly

hairs

• Hairy ligule

Giant Foxtail

• Note hairy ligule,

hair on leaf

sheath margin,

and hairs on leaf

surface

Green Foxtail

• Annual

• Short seedhead

• Hairy ligule

• Leaf surface

generally smooth

Green Foxtail

• Thin hairy ligule

• Hair on leaf

sheath margin

Wild Proso Millet

• Annual

• Seedling often looks

like corn plant

• Hairy ligule

• Shiny seeds tan to

black

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Wild Proso Millet

• Hairy ligule

• Bristly hairs on

leaf sheath

margin

Large Crabgrass

• Annual

• Membranous

ligule

• Smooth stems

• Ability to root at

nodes

Large Crabgrass

• Membranous

ligule

• Leaf blade and

sheaths hairy

Quackgrass

• Perennial

• Leaf sheath &

blade nearly

hairless

• Short membanous

ligule

• Clasping auricles

Quackgrass

• Extensive

rhizome system

from a single

plant

Wild Buckwheat

• Annual

• Heart shaped

pointed leaves

• Triangular seeds

• Ochrea present

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Wild Buckwheat

• Ochrea

(hairless) at

leaf axil

Ladysthumb Smartweed

• Annual

• Alternate leaf

pattern

• Ochrea (papery

sheath) with

fringe of hairs

Ladysthumb Smartweed

• Stem bent back

to expose ochrea

with a fringe of

hairs

Pennsylvania Smartweed

• Annual

• Alternate leaf

pattern

• Ochrea (papery

sheath) without a

fringe of hairs

Pennsylvania Smartweed

• Ochrea (hairless)

Field Bindweed

• Perennial

• 3-cornered

triangualar leaves

• Deep spreading

root system

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Field Bindweed

• Note leaf shape

and flowers

Hedge Bindweed

• Perennial

• Leaves tend to be

more 5 cornered than

field bindweed

• Shallow extensive

root system

Hedge Bindweed

• Extensive but

relatively

shallow

rhizomes lead to

quickly

developing

patches of

bindweed

Eastern Black Nightshade

• Annual

• First leaves have purple undersides

• Similar to pigweed when young but no notch at tip of leaf

• Prolific producer of berries that turn from green to purple to black

Bitter Nightshade

• Perennial

• Produces woody tissue

• Young leaves

• Older leaves

• Berries that turn from green to red

Redroot Pigweed

• Annual

• Leaves have small

notch at tip

• Petioles generally

have purple

coloration

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Prostrate Pigweed

• Annual

• Glossy small

leaves

• Red petiole

coloration

• Spreads out along

soil surface

Common Ragweed

• Annual

• Finely divided

lacy leaves

• Very thick

cotyledons

Giant Ragweed• Annual

• Mature leaves

are 3-lobed

• Mature height

up to 15 feet

Broadleaf Plantain

• Perennial

• Low growing

• Broad, simple leaves

• Common in lawns, often in shaded areas

Velvetleaf

• Annual

• Alternate heart

shaped leaves with

serrated margins

• Stem and leaves

densely hairy

Common Lambsquarters

• Annual

• First 2 leaves are opposite, later leaves are alternate

• Cotyledons and leaves covered with white, mealy granules

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Ground Ivy

• Perennial

• Often referred to as “creeping charlie”

• Small bluish-purple flowers borne in leaf axils

Common Purslane

• Annual

• Opposite leaves with

each pair rotated

around the stem 90o

from previous pair

• Thick fleshy leaves

w/o hair

• Red prostrate stems

Pineappleweed

• Annual

• Stems smooth

• Leaves finely divided,

smell like pineapple

when bruised

• Greenish-yellow

flowers

Common Yellow Woodsorrel

• Perennial or annual

• Stems hairy, may

root at joints

• Leaves with long

petioles, divided

into 3 heart-shaped

leaflets

Jimsonweed

• Annual

• Leaves are smooth and alternate

• Hypocotyl (stem below cotyledons) is very hairy

• Plant has unpleasant odor when crushed

Jimsonweed

• Seed pod

• Leaf shape

• Large white

flowers

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Carpetweed

• Annual

• Smooth green stems branching along ground forming circular mat

• Leaves in circles of 5 or 6 at each joint of stems

Common & Mouse-ear

Chickweed

• Annual

• Pictured: left-

common, right-

mouse-ear

• Petioles with line of

hairs on one side

Jerusalem Artichoke

• Perennial

• Fibrous roots with

rhizomes and tubers at

tips

• Hairy stems up to 9 foot

• Leaves very hairy

• 2-3 inch yellow flowers

similar to sunflower

Jerusalem Artichoke

• Mature plant

Jerusalem Artichoke

• Large roots and

tubers contain

extensive energy

reserves (hard to

kill)

Bull Thistle

• Biennial

• First leaves are oval

with a rough,

bumpy surface

• Adult leaves form

rosette, with dense

hairs on undersides

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Musk Thistle

• Biennial

• Adult leaves

forming rosette with

whitish margin

• Dense hairs on leaf

upper and lower

surfaces

Canada Thistle

• Perennial

• Leaves are alternate

with crinkled edges

and spiny margins

• Spreads with

rhizomes

Canada Thistle

• Note very wavy

leaf margin

Canada Thistle

• Rhizomes often

lead to thick

patches

INVASIVE PLANTSIN

WISCONSINKelly Kearns

Plant Conservation Program ManagerEndangered Resources Program

Wisconsin Department of Natural Resourceskearns@dnr.state.wi.us

608-267-5066

INVASIVE PLANTS are non-indigenous species or strains

that become established in natural plant communities and

wild areas and replace native vegetation.

EXOTIC/NONNATIVE PLANTS are species that have

been purposefully introduce for medicinal, agricultural

and/or ornamental purposes, or have been introduced accidentally.

NATIVE PLANTS are indigenous species naturally

occurring in a specific area or plant community, not

introduced.

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ECOLOGICAL IMPACTS OF INVASIVE PLANTS

• Displaces native vegetation

• Limits tree regeneration in forests

• Degrades wildlife habitat

• Contributes to endangerment of rare plant and animals

• Homogenizes the landscape

Kudza invades a forest

Reed Canary Grass

invades a wetland

SOCIO-ECONOMIC IMPACTS OF INVASIVE PLANTS

• Recreational boating and fish habitat disrupted.

• Decreased aesthetics resulting in loss of tourism.

• Hunting/hiking land rendered impassable by invasive shrubs.

• Long-term forest production declines due to tree seedlings

being outcompeted.

• Human health concerns from toxic and allergenic plants.

• Pastures degraded.

• Agricultural cost of controls and loss of production.

Purple Loosestrife

•

Buckthorn

Invasive Plants Association of Wisconsin (IPAW)

Categories of troublesome plants:

Weeds

Known Invasive Plants

Potentially Invasive Plants

Sometimes Invasive Natives

CONTROL METHODS:

• Manual- pull out, cut, girdle, graze, burn

• Mechanical- mow, plow, scrape

• Chemical- foliar, cut stump, basal bark herbicide

application

• Biological- use of natural insects or diseases

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Common Buckthorn Glossy Buckthorn(Rhamnus frangula)(Rhamnus cathartica)

Glossy

Buckthorn

Buckthorn

The leaves of Glossy Buckthorn are a more vibrant

green and are glossy or shiny compared to the dull leaves of

Common Buckthorn. Glossy Buckthorn leaves also lack the

small teeth found on Common Buckthorn.

Ken

neth

J. S

yts

ma

(Rhamnus cathartica)

(Rhamnus frangula)

Tartarian honeysuckle (Lonicera tatarica)

Michael Clayton

Kennith J. Sytsma

Autumn Olive(Elaeagnus umbellata)

Oriental bittersweet (Celastrus orbiculatus)

TNC

TNC

TNC

Garlic mustard (Alliaria petiolata)

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Dame’s rocket (Hesperis matronalis)

Dennis D. Horn

Multiflora Rose

(Rosa multiflora)

Black locust (Robinia pseudoacacia)

Michael Clayton

Robert W. Freckmann

William S. Justice

Japanese Knotweed (Polygonum cuspidatum)

Spotted knapweed (Centaurea maculosa)

K.Holmes-GLIFWC

Miketyler Jr.

Leafy spurge (Euphorbia esula L.)

Norman E. Rees, USDA ARS

Leslie J. Mehrhoff

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Wild parsnip (Pastinaca sativa)

Kitty Kohout

Crown vetch (Coronilla varia)

Dan Tenaglia

Dan Tenaglia

Bird’s-foot trefoil (Lotus corniculatus)

Richard Baur

Photographer: B. Eugene Wofford

© 2001 Steven Thorsted

Reed canary grass (Phalaris arundinacea)

Paul E. Berry

© 1997 Purdue University Agronomy Extension

Common Reed Grass (Phragmites australis)

Native Broad-LeafNarrow-Leaved Hybrid Cattail

NRC S

(Typha latifolia)(Typha x glauca)(Typha angustifolia)

Notice the difference in both the width of the leaves and the spike and also the

distance between the staminate and pistillate portions of the spike in each species.

NRC SNRC S

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Purple loosestrife (Lythrum salicaria)Eurasian watermilfoil (Myriophyllum specatim)

Robert L. Johnson

Robert H. Mohlenbrock

Alison Fox

Curly-leaf pondweed (Potamogeton crispus)

Virginia Kline

Curly-leaf pondweed (Potamogeton crispus)

Virginia Kline

INVASIVE COMMON GARDEN

PLANTS

Japanese barberry (Berberis thunbergii)

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Common tansy (Tanacetum vulgare)

Herbal Nexus

Yellow Iris (Iris pseudacorus)

Paul Drobot

Paul Drobot

Lily of the valley (Convallaria majalis)

Orange daylily (Hemerocallis fulva)

Britt Slattery

Dan Tenaglia

Common periwinkle (Vinca minor)

USDA NRCS Archives

Moneywort(Lysimachia

nummularia)

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White poplar (Populus alba)

Michael Clayton

Robert W. Freckmann

Potential

New

Invaders

Great Lakes Early Detection Network

(GLEDN)

(www.gledn.org or Mobile App)

• To find, report and control invasives BEFORE

they become serious problems.

• Target plants: 1) New invaders, and 2) Ones

already here, but in small numbers or limited areas.

• Develop a model for early detection and response

that can be adopted by other states.

TARGET SPECIESUpland

-- Common Teasel (Dipsacus fullonum) [WI]

-- Cut-leaved Teasel (Dipsacus laciniatus) [WI]

-- Giant Hogweed (Heracleum mantegazzianum) [WI]

-- Japanese Hops (Humulus japonicus) [WI]

-- Japanese Stilt Grass (Microstegium vimineum)

-- Wine Raspberry (Rubus phoenicolasius)

-- Japanese Hedge-parsley (Torilis japonica) [WI]

-- Spreading Hedge-parsley (Torilis arvensis)

-- Black Swallow-wort (Vincetoxicum nigrum) [WI]

-- Pale Swallow-wort (Vincetoxicum rossicum)

Common Teasel(Dipsacus sylvestris)

. kelly S Kearns

Stephen L. Solheim

Cut-leaved Teasel(Dipsacus laciniatus L.)

Wisconsin DNR

Wisconsin DNR

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Giant Hogweed (Heracleum mantegazzianum)

Donna R. Ellis

Terry English

Donna R. Ellis

Hedge Parsley (Torilis japonica, T. arvensis)

Japanese Stilt Grass(Microstegium vimineum)

Japanese Hops(Humulus japonicus)

TARGET SPECIESAquatic/Wetland

-- Flowering Rush (Butomus umbellatus) [WI]

-- European Marsh Thistle (Cirsium palustre) [WI]

-- European Frog-Bit (Hydrocharis morsus-ranae)

-- Hydrilla (Hydrilla verticillata)

-- Water Chestnut (Trapa natans)

European Marsh Thistle(Cirsium palustre)

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Flowering rush (Butomus umbellatus)

Kitty Kohout

Water Hyacinth (Eichornia crassipes)

Douglas Barbe

Jeff Abbas

Hydrilla (Hydrilla

verticillata)

Others not yet widespread

in Wisconsin

Tree of Heaven (Ailanthus altissima)

Dennis W. Woodland

Porcelain Berry

(Ampelopsis

brevipedunculata)

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Japanese Honeysuckle(Lonicera japonica)

Michael Clayton

Lowell Urbatsch

Amur honeysuckle (Lonicera maackii)

James H. Miller, USDA Forest Service, www.forestryimages.org

Herman, D.E. et al. 1996

Herman, D.E. et al. 1996

Giant Knotweed(Polygonum sachalinensis)

Emmet J. Judziewicz

Emmet J. Judziewicz

Garden Heliotrope (Valeriana officinalis)

Paul E. Berry

Richard Bauer

Burning Bush (Euonymus alatus )

Photos by James H. Miller

Without earthworms With earthworms

Photos and diagram courtesy of

University of Minnesota Agricultural

Experimental Station