Urban Guide

to

Weed Control

Macdonald and Louise/RoblinWeed Districts of Manitoba

Pest ManagementRegulatory Agency

Weed Control for Your Yard“One year’s seeding means seven years weeding” contains agreat deal of truth. That’s because seed reproduction is themost common way in which weeds spread. The best way tocontrol weeds is to simply prevent them from going to seed.Unfortunately, this prescription does not apply to all weeds.Some perennials reproduce from plant parts like rhizomes(reproductive roots), runners and tubers or other plant parts.Therefore, it’s important to know what the weeds are, andwhether they are annual, biennial, or perennial when planninga control program. It is also important not to introduce, or bringin, weeds by using weedy plants as ornamentals. Someexamples of such plants with weedy natures include purpleloosestrife, ox-eye daisy, scentless chamomile, creepingbellflower and toadflax.

This guide provides general measures that can be applied tothe control of many urban weed problems. These measurescan include both cultural (non-chemical) and chemical control.Weed control chemicals (herbicides) should be usedjudiciously, and according to the directions on the productlabel. The label indicates appropriate safety precautions thatshould be taken.

General IdentificationAnnual Weeds:• Reproduce solely by seed; they germinate, flower, and die

in one season.• Prevention and control is easier, since they usually

reproduce only by seed. Controlling the seeds helpseliminate future weed problems.

• Examples include pineapple weed, prostrate knotweed,purslane, lamb’s-quarters and ragweed.

Biennial and Winter Annual Weeds:• Reproduce by seed, they typically germinate in one year,

flower in the next year and then die.• Winter annuals typically germinate in late summer or fall.

Some winter annual weeds will also grow as annualplants. Biennials use two full seasons to produce seeds.

• Control of these plants when they are in the seedlingstage is important.

• Able to survive over the winter and other adverseconditions due to a thickened storage root.

• Some common winter annual weeds are flixweed,shepherd’s-purse, and stinkweed (pennycress). Burdockis a common biennial weed.

Perennial Weeds:• Regrow each year despite losing all above ground growth

to frost. Most perennials reproduce both by seed andvegetative parts.

• Have tap roots (like a carrot) or underground tubers, bulbsor rhizomes. “Creeping” perennials can travel under orover soil, spreading very rapidly from the original plant.

• Roots that often contain large quantities of stored energy,which allows them to survive overwinter.

• Infrequent cultivation enhances the problem by spreadingroots and other plant parts, which can grow and establishanother weed patch.

• Examples include dandelion, plantain, purple loosestrife,Canada thistle, creeping Charlie and quackgrass.

General Guidelines for Non-Herbicide Controlof Weeds

Lawns:• A vigorous healthy lawn will help prevent weed

establishment and growth.• Keep lawns well watered and adequately fertilized. Water

periodially for a sufficient length of time to provide for deeppenetration, rather than watering each day for shortperiods of time which results in shallow penetration. Claysoils will require several short waterings (15 min) with shortrest in between to prevent runoff into sewers.

• Mowing too low will reduce vigour and plant competition.• Reseed any thin spots to ensure good grass cover.• Remove weeds early, getting as much of the root as possible.• Ensure any soil used is free of weed seeds and

reproductive roots.• Address any new weeds immediately – before they spread.

Note: Do not use grass clippings for mulching or compostingfrom the first two cuttings after applying herbicide. Treatedclippings may contain herbicide residue.

Gardens:• Provide adequate water so plants can compete against

weed growth.• Fertilize with well-composted manure (which has fewer

weed seeds) rather than fresh manure.• Fully compost or otherwise dispose of any weed material.• Mulches and ground covers can smother weeds and help

to conserve soil moisture.• Ensure any soil used is free of weed seeds and rhizomes.• Eliminate perennial weeds from creeping into the edge of

the garden.• Remove annual weeds early – the best method of control

is to eliminate weeds before seed is produced.

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Guidelines for Using Herbicides to ControlWeedsSome weeds require herbicides to control them, but it’simportant to use chemicals (herbicides) carefully so that youdon’t damage other plants. Remember that:• Herbicides do not distinguish between weeds and

desirable plants and will kill any susceptible plants theycontact.

• Non-selective herbicides (those containing the activeingredient glyphosate, for example) can kill any plantsthey touch.

• Selective herbicides kill certain weeds and leave otherweeds and plants unharmed. They can damage desirableplants if used improperly.

Pesticide applications can impact soil and plants. Theeffectiveness of the application depends onenvironmental conditions. Always adhere to the followingguidelines and read and follow label directions forherbicide use.• Identify the weed to be controlled.• Use only pesticides labelled “domestic” for home ground

use.• Follow labelled mixing directions.• Observe the labelled time interval before harvesting

garden produce.• Always mix herbicides outdoors, and use safety

equipment as stated on the product label.• Do not spray herbicides on windy days or when there is

no wind. Its best to spray under moderate conditions suchas a gentle breeze, blowing away from sensitivevegetation.

• If plants are not actively growing because environmentalconditions are poor (too cold, hot, wet or dry), resultingweed control may be unsatisfactory.

• Keep children and pets away from treated area for up to24 hours.

• If you hire a professional for a herbicide application, makesure the person or company is qualified — and holds theproper licenses.

• If you spill a large amount of herbicide (or have any otherherbicide accident that could affect the environment), call1-204-945-4888 in Manitoba; 1-306-667-7525 inSaskatchewan.

Note: Use a separate sprayer to apply herbicides and otherpesticides. Small amounts of herbicide in a sprayer can injuredesirable plants!

Types of Do-It-Yourself Herbicide ApplicatorsHand-Held SprayerThis type of sprayer is the most common applicator used byhomeowners, and is best for spot treatment of weeds. Itconsists of a container, an air pump, a hose, and a nozzle.Usually the herbicide is mixed with water. Some herbicidesare sold in a pre-mixed, ready-to-use, hand-held spray bottle,which is disposed of when empty.

Backpack SprayerThis type of sprayer is useful for a variety of applications. Itconsists of a 3 to 4 gallon tank, a pump mechanism, a spraywand, and a harness that permits the sprayer to be carried onyour back. The tank of this sprayer is not under pressure. It ispumped with one hand, and the sprayer wand is held with theother. Pressure can be regulated by the amount of force usedin pumping. Herbicides are generally mixed with water andapplied in a diluted form.

Hose-End SprayerGenerally, this type of sprayer results in the use of moreherbicide than other types of applicators. It is better forapplying fertilizers than herbicides.

Wipe-On ApplicatorThis allows the selective application of herbicides. A smallamount of herbicide is wiped on a few leaves of the plant. Theherbicide flows by gravity through small holes onto theapplicators’ absorptive surface (such as foam sponge or wickrope), and is then rubbed onto the weeds. An advantage isthat drift is virtually eliminated. A disadvantage is that the plantmust be in contact with the applicators’ surface. Not allherbicides can be used in this type of applicator.

Play it Safe When Using HerbicidesHerbicides are designed to control unwanted plants and aregenerally very safe to the person using them and theenvironment. Herbicides are less toxic to people than otherpesticides such as insecticides because plants are verydifferent from people. However, herbicides, like any chemical,should be regarded as potentially hazardous to anyonecoming into contact with them. Proper care should be taken toensure your safety — and the safety of others — whenapplying herbicides. Handle with care.

Read the LabelAll pesticides that are sold in Canada must be registeredthrough Health Canada and under the Pest Control Products(PCP) Act. The label on the herbicide container has a greatdeal of important information that you should read thoroughly.Label information includes: identity (guarantee) of the activeingredient(s); directions for safe use; personal and protective

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equipment, first aid, caution and warning information; nameand address of the manufacturer; product warnings anddisposal. It is illegal to use a pesticide in a manner that is notspecified on the label.

Handle with CareBefore handling (mixing, pouring, etc.) herbicides, refer to thelabel regarding adequate protective clothing and handlinginstructions. Always mix or pour herbicides outdoors.

Avoid Personal ContactSome other important safety considerations include:• Never eat, drink, or smoke while applying herbicides.• Wash hands and other exposed body parts immediately

after the application is completed.• Remove your clothing after applying herbicides, shower,

and put on clean clothes. Launder potentiallycontaminated clothing separately from the family wash.

• Immediately remove contaminated clothing and wash skinarea with soap and water if an accidental splash or spilloccurs.

• In most cases a treated area may be entered after theherbicide has dried. However, it is a good idea to stay offthe treated area for up to 24 hours as a precaution.

Store ProperlyHerbicides (and other pesticides) should always be stored intheir original containers. When mixing for use, do not mix anymore than needed for the job at hand. Label spray applicatorsused for herbicides and do not use them for other pesticides.Check containers periodically for leaking, and properlydispose of any that are damaged. The shed/garage in whichthey are stored should be located away from the house, andshould be kept locked. Do not allow children or pets to accessthis building.

All empty herbicide containers should be triple rinsed, andsafely stored until they can be disposed of according to locallyapproved regulations.

Know Emergency ProceduresIf anyone accidentally ingests or is overly exposed to aherbicide, seek medical help immediately. Check the label forfirst-aid treatment. There is an emergency number on the labelto call for information. Take the herbicide label with you to thehospital.

Weed IdentificationBlack Medic: An annual that reproduces by seeds. Stems lieflat to the ground, spreading widely and can be upto 2.5 feet long. Many small yellow flowers createa large seed head. Leaves are three lobed,similar to a cloverleaf.Non-Chemical Control: Mowing will nothelp control this low-growing plant. Inboth lawns and gardens, dig out thewhole plant. In lawns,maintaining healthygrass is important.Chemical Control:Herbicide containing amixture of 2,4-D, mecopropand dicamba will control thisweed before it flowers. Do not usethese products in garden areas.

Burdock: A biennial that reproduces by seeds. Forms acluster of leaves (rosette) the first year then matures in thesecond year and forms seed in aburr. It grows from 1-6.5 ft. tall.First year leavesresemble rhubarb andhave a woollytexture on theunderside. Secondyear plants standstraight up and stemscan be red-coloured.Non-Chemical Control:Dig the plant and root outof the ground duringthe first year. In thesecond year cut offthe seed stalks to prevent seed formation.Chemical Control: Herbicide containing 2,4-D and dicambawork to some degree during the first year (rosette). There isno adequate herbicide control during the second year. Do notuse these products in garden areas.

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Canada Thistle: A perennial that reproduces by horizontalroots and seeds with white fluff. Usually 1-4 ft. tall, flowers arepink to purple and leaf edges are jagged, with short spines.Non-Chemical Control:Maintain a vigorous lawnfor competition and mowregularly. Very small,individual plants may beremoved. In gardens,mechanical (non-chemical) methods arenot effective on patches,because theypromote moreroot growth.ChemicalControl:Herbicidescontaining 2,4-Dand dicambagive somesuppression, but repeated applications may be required inlawns. In gardens, non-selective products (glyphosate) can beused where desirable plants are not present. Late summer isthe best time for control because root reserves are at theirweakest at this time. After application, do not disturb weeds forat least a week to allow the herbicide to move into the roots.Trim flowers to prevent seed production.

Chickweed: An annual or occasionally a winter annual thatreproduces by seeds and creeping stems. Tangled stems lieflat to the ground with many branches from 3-20 inches long.White flowers have 5 petals. Small heart shaped leaves areopposite each other.Non-Chemical Control: Not usuallya problem in cultivatedgarden areas, sinceregular tillage willcontrol it. In otherareas remove entireplant regularlybecause it canregrow. Does well in moistshaded areas.Chemical Control: In lawns, herbicides containing 2,4-D &mecoprop can be useful when applied in late spring or earlysummer, before flowering. Do not use these products ingarden areas.

Common Groundsel: An annual orbiennial that reproduces by seeds. From1-3 ft. tall, with yellow flowers appearingfrom late spring until late fall. Leavesalternate on the stem and are deeplydivided into irregular lobes.Non-Chemical Control: More of aproblem in gardens than lawns.Remove by pulling, hoeing or tillingbefore seeds are produced.Chemical Control: Productscontaining 2,4-D, mecopropand dicamba can be used inlawns, if required, beforeflowering. Do not use theseproducts in garden areas.

Creeping Bellflower: A perennial that reproduces by rootsand seeds. Generally 1-2 ft. tall with bluish-purple, bell shapedflowers. Leaves can be confused with creeping Charlie whenthe plant is short, but become longer and more pointed as theplant gets taller. Individual stems are unbranched.Non-Chemical Control: Dig out the entire plant as roots canregrow. In gardens, continuous cultivation helps reducegrowth.Chemical Control: Herbicidescontaining dicamba can be used,but repeated applications may berequired. Do not use theseproducts in garden areas.

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Foxtail Barley: A native perennial grassthat reproduces by seed. Narrow leavesgrow in a clump. Seeds have long finebrush-like hairs which make the seedheadlook like a “tail.”Non-Chemical Controls: Can be removedby regular tillage. This plant can also bedug out effectively.Chemical Controls: Non-selectiveherbicides (glyphosate) can be used wherethere are no other plants nearby.

Lamb’s-quarters: An annual that reproduces byseeds. Generally 2-4 ft. tall with a small andinconspicuous green flower that has no petals.Leaves are often covered with a mealy powder,especially on the undersides, and leaf edgesare wavy.Non-Chemical Control: Emerges throughoutthe growing season, but is easily controlled byhoeing, tillage or mowing on a regular basis.Chemical Control: Herbicides containing 2,4-Dwill work effectively. Do not use these products ingarden areas. Non-selective herbicides work wellin gardens.

Pineapple Weed: An annual weed that reproduces by seeds.Short, 0.3-1.3 ft. tall, with yellow-green flowers in a cone-shapedhead. Feathery leaves alternate on branching stems and canhave a distinct pineapple scent. Usually a problem along theedge of driveways.Non-Chemical Control:Easily controlled byremoval beforeseeds are produced.In gardens, hoeingor tillage works well.Chemical Control:Herbicides containing2,4-D or MCPA cancontrol this weed butare not normallynecessary. Do not usethese products in gardenareas.

Creeping Charlie: A perennial that reproduces by creepingstems and seeds. Stems are low to the ground, forming adense ground cover, with floweringbranches and spread 1-2.5 ft. Flowersare light blue to bluish-purple andleaf edges have shallowrounded teeth.Non-Chemical Control: Handpulling rarely eliminates this weed inlawns. In gardens, regular tillagewill reduce growth.Chemical Control: Susceptibleto products containing dicamba,but repeated applications maybe necessary. Do not usethese products in gardenareas.

Dandelion: A perennial that reproduces by seeds carried onwhite fluff. It is short to the ground with yellow flowers on ahollow milky stem. Leaves grow ina cluster and have jagged edges.Non-Chemical Control:Susceptible to tillage, sois not usually a problemin gardens. Maintaina vigorous lawn forcompetition.Young plantscan be dug outbut all the rootmust beremoved. Mowingwill not help, as dandelionscan grow and flower very closeto the ground.Chemical Control: Herbicidescontaining 2,4-D will controldandelions in the lawn. Fallapplication is best, wellbefore a killing frost, or inearly spring before flowering. Do not use these products ingarden areas. Herbicides containing ghyphosate work well ingardens, but may require repeat applications.

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Plantain (Broadleaf Plantain): A short perennial thatreproduces by seeds. Stemlessoval leaves form a cluster.Flowers are greenish and growon a single spike up to 16 inchestall.Non-Chemical Control:Maintain a healthy lawn and mowregularly to reduce seeddevelopment. Timely hoeing inthe garden is very effective.Chemical Control:Herbicidescontaining 2,4-Dmay help. Thisweed is notsusceptible todicamba. Do not usethese products in gardenareas.

Prostrate Knotweed: An annual that reproduces by seeds.Usually short and flat to the ground, but can be slightly raisedor erect. Many oval leaves alternate on the stem. Grows inhard-packed areas.Non-Chemical Control:Maintain a healthylawn and aeratecompacted areasto stimulate grassgrowth.Hoeing ortillage workswell in the garden,remove before seed isproduced.Chemical Control: Herbicide mixtures containing 2,4-D,dicamba and mecoprop are best used when in the seedlingstage. Do not use these products in garden areas.

Purple Loosestrife (Lythrum): A perennial that reproducesby seeds and rhizomes. It is 1-8 ft. tall with rose-purple spikes of flowers. A serious problem thatcan overtake native vegetation in marshes,ditches, and other wildlife nesting areas. Allplants—regardless of locations and variety—should be destroyed to prevent reproduction.This weed is highly prolific in wet areas, socare should be taken to prevent it fromgoing to seed.Non-Chemical Control: Removethe whole plant, using a spade toensure getting as much of the rootsas possible. This plant can regrowfrom the stem or small amount of theroot. Plant parts should be sealed in aplastic bag. For disposal, callyour local weed control authority(city, town or municipality). Donot compost. Watch the spot forseveral years and remove any re-growth.Chemical Control: Non-selective herbicides(glyphosate) can be used, but only on dry areas where thereare no desirable plants. Complete plant removal is still themost effective method.

Purslane (Portulaca): An annual that reproduces by seedsand plant fragments. Stems grow flat to the ground, up to 2 ft.long. It has yellowflowers and leavesare small and fleshy.Non-Chemical Control:Remove all plant partssince cut pieces or leavescan root, grow andproduce seed.Chemical Control:Herbicides containing 2,4-D or MCPA may controlthis weed in theseedling stage only.Do not use theseproducts in gardenareas.

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Quackgrass: A perennial grass that reproduces by seeds orrhizomes that form patches. Up to 3.5 ft. tall, with flat hairlessleaves.Non-Chemical Control: Root rhizomes arevery prolific, care must be taken to removeall root material from the soil. In lawns,frequent mowing will suppress quackgrass,but will not eliminate it.Chemical Control: Non-selectiveherbicides (glyphosate) are effective.If the infestation is severe, a completelawn renovation may be required. Ingardens, spot spray the patches withglyphosate that are not near desirableplants. These areas may require reseeding.

Round-Leaved Mallow: An annual or biennial thatreproduces by seeds. Stems grow along the ground up to1.5 ft. long, branching at the base. Flowers are usuallywhite with dark violet veins,and the seedpodresembles awheel of cheese.Leaves alternateon the stem andare heart shapedwith scalloped edges.Seeds have been reorded tolast up to 100 years in the soil.Prevent seed production.Non-Chemical Control: Hoeing ortillage is the most effective during the seedling stage. Oncethe weed becomes established, it is difficult to removebecause of its deep taproot. Mowing in lawns is not effectivebecause of the weed’s low growth.Chemical Control: Can be controlled in lawns with herbicidescontaining 2,4-D, dicamba and mecoprop. Do not use theseproducts in garden areas.

Scentless Chamomile: Usually a perennial that reproducesby seed. Can also act as an annual or biennial, growing,producing seed and dyingin 1 or 2 seasons. Manydaisy-like white flowers.Leaves are feathery.Non-Chemical Control:Pulling, hoeing and tillingwork well in the garden,remove before seed isproduced. Mowing will notentirely control this weedbut may help reduce theamount of seed produced.Chemical Control: There are noeffective chemical controls for this weed.Glyphosate can have limited success ifapplied when the plants are young.

Shepherd’s Purse: An annual or winter annual, reproducingby seeds. Usually germinates in the fall, young plants aredormant over the winter, and then matureand produce seed early the followingspring. Flowers are white and theseedpod is a distinctive heartshape. Leaves alternate on thestem and are lobed, edges can betoothed to smooth.Non-Chemical Control: Removebefore seed is produced. Fallremoval will destroy seedlings andprevent early ripening the followingspring and summer.Chemical Control: Herbicides containing2,4-D or MCPA are effective whenweeds are in the seedling stage,in late fall or early spring onsmall plants. Do not use theseproducts in garden areas.

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Stinkweed: An annual or winter annual reproducing by seed.Leaves have a distinct odor (hence the name). Flowers aresmall and white, with leaves firstappearing in a cluster (rosette) thenlater the stem stretches up. Plantheight is variable.Non-Chemical Control:Remove before seed isproduced. This weed germinatesall season long, so control mayhave to be repeated.Chemical Control: Herbicidescontaining 2,4-D or MCPA areeffective when weeds are in theseedling stage, in late fall orearly spring on small plants. Donot use these products in garden areas.Non-selective herbicides are effective ingardens, away from desirable plants.

White Dutch Clover: A perennial that reproduces by aboveground stems and seeds. Short, 2-6 inches tall with clusters ofsmall white flowers. Three leaflets with serrated edges makeup each leaf. Stems arecreeping and matted.Non-ChemicalControl:Mowing willreduce plantmass but will not doany long-term harm tothe plant. Dig out theentire plant ifinfestations areminor.Chemical Control:Use a herbicidecontaining mecoprop. Do notuse these products in garden areas.

Controlling Other Vegetation Problems

MossesIn lawns, low fertility, poor drainage and lack of sunshinehamper grass growth and encourage moss growth. Forcontrol: rake early to remove moss; aerate soil, and fertilize;improve drainage; reduce shade where possible by pruningtrees and shrubs.

Unwanted TreesUnwanted trees should be manually removed after they havefully leafed out. Their leaves cannot be sprayed with aherbicide for fear of drifting on desirable vegetation.

After removal as close to the ground as possible, the rootmust be killed to prevent suckering. Do this by drilling holes 1cm deep in the wood near the bark of the stump, filling it with2,4-D, and then covering with clay. The herbicide will moveinto root system and kill the suckers as they develop.

Once the stump is killed, it can be left to the elements; naturaldecay-causing organisms will gradually break it down.

MushroomsMushrooms are actually a fungus — and not a weed;therefore, they are not controlled by herbicides. The presenceof mushrooms is often an indicator of wet soil conditions. Inlawns, aerating will help. Mushrooms feed off old decayingwood (e.g., stumps and roots from dead and dying trees).

Noxious Weeds

Both Manitoba and Saskatchewan have legislation thatmandates owners and occupants to prevent the growth,ripening and spread of weeds and weed seeds. Thelegislation is called the Noxious Weeds Act. Noxious weedsare considered to be a threat to agriculture, human health, orthe environment due to their invasive nature or toxicproperties. Further information on this legislation can be foundthrough municipal or provincial agricultural staff or fromManitoba or Saskatchewan’s web sites. Manitoba’s NoxiousWeed Act can be found at: www.gov.mb.ca/chc/statpub/free/pdf/n110.pdf and in Saskatchewan at: www.qp.gov.sk.caand search Free Law for “Noxious.”

For more information on home gardens, contact:

University of Manitoba Horticulture Line 1-800-432-1960University of Saskatchewan Garden Line 306-966-5865

Printed March 200320M CD0118

Macdonald and Louise/RoblinWeed Districts of Manitoba

Acknowledgements:This publication was made possible by thePest Management Regulatory Agency (PMRA) throughthe Pesticide Innovation Fund.

Written and reviewed by:Saskatchewan Agriculture, Food and Rural Revitalization;Manitoba Agriculture and Food;Macdonald Weed District of Manitoba; andLouise/Roblin Weed District of Manitoba

Pest ManagementRegulatory Agency