Invasive species

On this page

What are invasive species?

Species which are quick to reproduce and spread, and which thrive in a broad range of habitat conditions, can often out-compete other species. These species are called “invasive” due to their aggressive colonisation of new spaces. Although some native species could be considered invasive, they are usually kept in check by the natural balance of their local ecosystem, and are not of great concern compared to non-native invasive species. Humans have transported many species to new lands, whether deliberately in the case of livestock, pets, crops and garden plants, or inadvertently in the case of many species commonly regarded as pests. These non-native species may have no local predators to control their spread, or may have devastating effects on local species which have not adapted to resist them. They can have serious impacts on the ecological balance of their new home.

Many non-native invasive species have already reached Ottawa. Garlic mustard, swallow-wort (also known as dog-strangling vine), common buckthorn and glossy buckthorn are common in many of our natural areas, crowding out the native species that should be there. Zebra mussels, Eurasian water-milfoil and flowering rush are thriving in our rivers. Other threats, such as the Asian long-horned beetle, are moving this way. Some species are still actively introduced, such as Norway maple and Amur maple, which are both popular landscape trees due to their attractive foliage and their ability to survive in highly urbanised environments. Others, such as the emerald ash borer that is decimating our city’s forests, are the subject of intensive research to find ways to control or eliminate them.

Wild Parsnip, Poison Ivy, and Giant Hogweed are commonly found in areas of uncultivated land, roadside ditches, nature trails, woodlots, and in some cases, on rural and residential property.  Under the Ontario Weed Control Act, the City is responsible to take some action regarding the control of Wild Parsnip, Poison Ivy and Giant Hogweed on city property. Private property owners are responsible for removing these plants from their own property. These plants are of public health concern because touching them or their sap can result in painful skin rashes and burns.  If you decide to take measures to control these plants, regardless of the method used, wear protective clothing and goggles to cover exposed skin and protect your eyes.  

Residents can help control invasive non-native species by becoming aware of them and acting to prevent or limit their spread. When camping, boating or cottaging, avoid transporting firewood or live bait into or out of the area, and clean all equipment thoroughly to remove seeds and other hitch-hikers. Never release unwanted pets into the wild. Choose native plants for landscaping where possible, and never plant non-native invasives (see some examples listed below) near natural areas. Ask your local nurseries and plant suppliers about which native species are best for landscaping, or use this handy ‘grow me instead’ guide.

Garden plants to avoid

The following popular garden plants are non-native invasives that should not be planted near natural areas:

  • Amur maple – Acer ginnala
  • Black locust – Robinia pseudoacacia
  • Bugleweed – Ajuga reptans
  • Creeping Jenny (moneywort) – Lysimachia nummularia
  • Common and Japanese barberry – Berberis vulgaris and B. thunbergii
  • Dame’s rocket – Hesperis matronalis
  • Day lily – Hemerocallis fulva
  • English ivy – Hedera helix
  • European linden – Tilia cordata
  • European mountain-ash – Sorbus aucuparia
  • Goutweed – Aegopodium podagraria
  • Honeysuckle, including Amur’s, Bell’s, European fly, Morrow and Tatarian (or Tartarian) – Lonicera maackii, L. X bella, L. xylosteum, L. morrowii and L. tatarica
  • Japanese Knotweed - Fallopia japonica
  • Lily of the valley – Convallaria majalis
  • Oriental bittersweet – Celastrus orbiculatus
  • Miscanthus grasses – Miscanthus sinensis and Miscanthus sacchariflorus
  • Norway maple (including red-leaved varieties) – Acer platanoides
  • Periwinkle – Vinca minor
  • Spotted deadnettle – Lamium maculatum

Plants not permitted in City rights of way

View a list of non-native invasive plant species that are not permitted to be used for landscaping within the City’s right of way:

For more information on how to dispose of invasive species, please go to Waste Explorer | City of Ottawa.

For more information on invasive species:


Wild parsnip

Public notice of herbicide use

The City of Ottawa intends to control wild parsnip in areas city-wide along rural and suburban roadsides. Spot spraying will continue throughout the summer months as needed within the City of Ottawa.

The program will use Clearview Herbicide (PCP #29752, containing aminopyralid and metsulfuron-methyl), Navius FLEX (PCP#30922, containing metsulfuron-methyl and aminocyclopyrachlor) and Gateway adjuvant (PCP# 31470, containing mineral oil – paraffin base (adjuvants), surfactant blend) under the Pest Control Products Act (Canada).

Treatment for wild parsnip will commence on May 27, 2024 weather permitting, and will end on October 31, 2024. The City has retained the services of Wagar & Corput Weed Control Inc to apply the herbicide.

For further information, please contact the City at 3-1-1.

Opting Out

If you own property adjacent to the areas being sprayed and choose to opt out of the program, please file an online opt-out request (one property per form) before May 9, 2024.

2024 Wild Parsnip Herbicide Strategy

Herbicide use locations

Road From To
8th Line Cooper Hill Road Bruce Street
8th Line Glenwood Drive Walker Road
9th Line Pana Road Victoria Street
9th Line Castor Road Marionville Road
Akins Shea Road Eagleson Road
Albion Maple Key Private Leitrim Road
Albion Findlay Creek Drive High Road
Anderson Dolman Ridge Road Ridge Road
Andrew Fourth Line Road James Craig Street
Ashton Street Highway 7 Ashton Street North Ormrod Road
Balmoral River Road Limebank Road
Bank Meadow Drive Popham Street
Bank Kennedy Road Belmeade Road
Barnsdale Borrisokane Road Greenbank Road
Barnsdale Eagleson Road Twin Elm Road
Becks Kinburn Side Road Dead End
Belmeade Dalmac Road Bank Street
Birchgrove Magladry Road Russell Road
Bleeks Dwyer Hill Road Conley Road
Borrisokane Cambrian Road Strandherd Drive
Boundary Burton Road Victoria Street
Bowesville Earl Armstrong Road Mitch Owens Road
Bridgestone Eagleson Road Windways Cres
Brownlee Shea Road Eagleson Road
Burnt Lands Dead End March Road
Cabin Nixon Drive Stagecoach Road
Callendor Fourth Line Road Dead End
Cambrian Old Richmond Road Moodie Drive
Canaan Colonial Road Larmours Road
Carp Russ Bradley Road William Mooney Road
Carroll Side Upper Dwyer Hill Road Peter Robinson Road
Carsonby Prince Of Wales Drive Dead End
Castor 9Th Line Road Yorks Corners Road
Century Fourth Line Road William Mcewen Drive
Century Trestle Street  
Clayton Russell Road Devine Road
Colonial Heuvelmans Road Dunning Road
Colonial Birchgrove Road Canaan Road
Conley Flewellyn Road Mansfield Road
Conroy Hunt Club Road Davidson Road
Cowell Malakoff Road Mccordick Road
Craig'S Side Donald B. Munro Drive Carp Road
Crawford Side Dwyer Hill Road Dead End
Dalmac Forest Road Springhill Road S
Dalmeny River Road Gordon Murdock Road
Dealership Strandherd Drive Dead End
Dearborn Lester Road Tranquil Streetream Private
Devereaux Swale Road Dead End
Devine Rockdale Road Clayton Road
Diamondview Donald B. Munro Drive William Hodgins Lane
Didsbury Campeau Drive Dead End
Dilworth Mccordick Road Rideau Valley Drive S
Donald B. Munro William Hodgins Lane Farmland Road
Donald B. Munro Meadowridge Circle Old Carp Road
Donald B. Munro Falldown Lane  
Donnelly Fairmile Road Fourth Line Road
Donnelly Beaman Lane Mccordick Road
Downey Rideau Road Mitch Owens Road
Dwyer Hill Strickland Private O'Neil Road
Eagleson Fernbank Road Romina Street
Eagleson Fallowfield Road Brophy Drive
Eagleson Eagleson Road Flewellyn Road
Earl Armstrong Canyon Walk Drive Limebank Road
Earl Armstrong   Bowesville Road
Fallowfield Old Richmond Road Steeple Hill Cres
Fallowfield Strandherd Drive Prince Of Wales Drive
Fallowfield Dwyer Hill Road Eagleson Road
Fawn Valley Tranquil Streetream Private Dearborn Private
Fernbank Shea Road Eagleson Road
Fernbank Jinkinson Road Etta Street
Fernbank Dwyer Hill Road Munster Road
Flewellyn Faulkner Trl Eagleson Road
Flewellyn Dwyer Hill Road Munster Road
Flewellyn Ashton Street Road Ormrod Road
Fourth Line Brophy Drive Donnelly Drive
Frank Kenny Huismans Road Rockdale Road
Franktown Dwyer Hill Road Perth Street
French Hill Frank Kenny Road Pleasantview Crt
French Hill Brennan Park Drive Birchgrove Road
Galetta Side Mohrs Road Carp Road
Garlock Third Line Road S Dead End
Garvin Huntley Road Shea Road
Golf Club Dwyer Hill Road Dead End
Gordon Murdock Cabin Road Lombardy Drive
Gordon Murdock Gowan Gt Dalmeny Road
Gourlay Old Carp Road Lady Lochead Lane
Greenbank Marketplace Avenue Half Moon Bay
Greenbank Barnsdale Road Viewbank Road
Gregoire Victoria Street Continuation Of Gregoire Road
Grey'S Creek Snake Island Road Dead End
Half Moon Greenbank Road Tucana Way
Hall Russell Road Piperville Road
Harbour Learmonth Avenue Galetta Side Road
Hedge All  
Hope Side Eagleson Road Old Richmond Road
Houston Hedge Drive Hedge Drive
Howie March Road Old Almonte Road
Huismans Frank Kenny Road Rockdale Road
Huntmar Old Carp Road Richardson Side Road
Innes Cox Country Road Dunning Road
James Craig Roger Streetevens Drive Prince Of Wales Drive
James Craig Dead End Andrew Street
Jock Dwyer Hill Road Munster Road
Jock Dead End Wood'S Road
Jockvale Greenbank Road Longfields Drive
Jockvale Transitway Bending Way
Jockvale Dead End Transitway
John Aselford Edith Margaret Place Marchurst Road
John Cavanaugh Carp Road Mcgee Side Road
Joy'S Garvin Road Franktown Road
Kettles All -
Kinsella Old Montreal Road Golightly Terr
Lady Lochead Gourlay Lane Old Carp Road
Lahey Old Second Line Road Dead End
Landel Marchvale Drive Maley Lane
Larmours Birchgrove Road Canaan Road
Leitrim River Road Bank Street
Lester Alert Road Bank Street
Limebank Leitrim Road Rideau Road
Limestone Dead End Styles Side Road
Lockhead Mccordick Road Rideau Valley Drive S
Longfields Abetti Ridge Paul Metivier Drive
Longfields Cambrian Road Prince Of Wales Drive
Lough Dagg Crt Wilhaven Drive
Mackey Viola Street Mccordick Road
Magladry Dunning Road Ruissellet Road
Malakoff Gallagher Road Donnelly Drive
Maley Marchvale Drive Old Second Line Road
Manotick Main Orchard Hollow Drive Island View Drive
Manotick Main Currier Street Firefly Lane
Manotick Main Island View Drive Century Road E
Manotick Street Mitch Owens Road Pebblewoods Drive
Manotick Street Pebblewoods Drive Apple Orchard Road
Manotick Street Elkwood Drive Deermeadow Drive
Manotick Street Nick Adams Road Snake Island Road
Mansfield Munster Road Conley Road
Maple Grove Huntmar Drive Silver Seven Road
March Diamondview Road Huntmar Drive
March Peter Robinson Road Howie Road
Marchvale Landel Drive Maley Lane
Margaret Anne March Road Locharron Cres
Marionville Bank Street Continuation Of Marionville Road
Marvelville Bank Street 8Th Line Road
Maxwell March Road Hedge Drive
Mayors Dead End Cenote Road
Mccordick Eagleson Road Century Road W
Mccordick Pollock Road Cowell Road
Mcdiarmid Louis-Forget Road Swale Road
Mcgee Side Carp Road Dead End
Mcgee Side Spruce Ridge Road David Manchester Road
Merivale Fallowfield Road Prince Of Wales Drive
Mitch Owens Bridge Street Limebank Road
Moodie Barnsdale Road Brophy Drive
Motor Works Dibblee Road  
Munster Munster Road Kettles Road
Munster Flewellyn Road Owlshead Road
Murphy Side Marchurst Road Old Second Line Road
Nixon Cabin Road Taylor Way
Oak Creek Mcgee Side Road Richardson Side Road
O'Keefe Dead End Lusk Street
Old Almonte Upper Dwyer Hill Road Corkery Road
Old Carp March Road Huntmar Drive
Old Coach Diamondview Road Donald B. Munro Drive
Old Montreal Regional Road 174  
Old Second Line Murphy Side Road March Road
Ormrod Ashton Street Road Flewellyn Road
O'Toole Wilhaven Drive Innes Road
Ottawa Colonel Murray Street Eagleson Road
Paauw Dead End Proven Line Road
Pana 8Th Line Road 9Th Line Road
Perrault Milton Road Trim Road
Perth Shea Road Eagleson Road
Perth Franktown Road Rochelle Drive
Peter Robinson Carroll Side Road March Road
Peter Robinson Dead End Vaughan Side Road
Phelan Third Line Road S Dead End
Philsar Dealership Drive  
Pierce Malakoff Road Mccordick Road
Pioneer Line Mcdiarmid Road Belmeade Road
Pollock Mccordick Road Fourth Line Road
Porteous Bank Street Dead End
Prince Of Wales Rocky Hill Drive Woodroffe Avenue
Prince Of Wales Barnstone Drive Waterbridge Drive
Prince Of Wales Deakin Street Holborn Avenue
Prince Of Wales Carsonby Road W Fourth Line Road
Proven Line Paauw Road Klondike Road W
Purdy Ashton Street Road Dwyer Hill Road
Queen Anne Dead End Merivale Road
Ray Wilson Yorks Corners Road Gregoire Road
Reevecraig Dilworth Road Continuation Of Reevecraig Road N
Richardson Side Oak Creek Road Terry Fox Drive
Rideau Spratt Road Downey Road
Rideau Valley Prince Of Wales Drive Bankfield Road
Rideau Valley Manotick Main Street Roger Streetevens Drive
Rideau Valley Fennell Lane Dilworth Road
Ridge Anderson Road Dead End
Ritchie Side Walter Bradley Road Upper Dwyer Hill Road
River Jarvis Drive Lowen Drive
River Ryeburn Drive Leitrim Road
River Bridge Street Cabin Road
Rockdale Colonial Road Forced Road
Roger Neilson Dead End Dead End
Roger Streetevens Dwyer Hill Road Malakoff Road
Royal Orchard Quillivan Lane Wilhaven Drive
Ruissellet Magladry Road Russell Road
Russ Bradley Carp Road Huisson Road
Russell Anderson Road Farmers Way N
Russell Hall Road Leitrim Road
Russell Spring Street Hall Road
Russell Rockdale Road Mcneely Road
Russell Ruissellet Road Langlade Road
Sarsfield Larmours Road Watson Road
Sarsfield Wilhaven Drive French Hill Road
Saumure Russell Road Devine Road
Second Line Carsonby Road E Phelan Road E
Shea Abbott Street E Flewellyn Road
Snake Island Stagecoach Road Bank Street
Soldier'S Munster Road Dead End
Southwick Rideau Valley Drive N Dead End
Springhill Blanchfield Road Bank Street
Stagecoach Cabin Road Old Stagecoach Road
Stagecoach Dalmeny Road Kaycourt Drive
Stonewalk Dead End Panmure Road
Swale Snake Island Road Mcdiarmid Road
Tall Forest Pineridge Road March Road
Tenth Line Continuation Of Tenth Line Road Navan Road
Terry Fox Castlefrank Road Eagleson Road
Third Line Century Road W Dead End
Third Line Stratton Drive Roger Stevens Drive
Thomas A. Dolan Rachell Way Carp Road
Twin Elm Dead End Cambrian Road
Upper Dwyer Hill Hamilton Side Road Mcarton Road
Upper Dwyer Hill Vaughan Side Road Carroll Side Road
Upper Dwyer Hill Mantil Side Road Vaughan Side Road
Upper Dwyer Hill Kinburn Side Road Grainger Park Road
Vaughan Side Shanna Road Donald B. Munro Drive
Vaughan Side Burnt Lands Road Marshwood Road
Victoria Bank Street Andrew Simpson Drive
Viewbank Barnsdale Road Greenbank Road
Watson Dunning Road Sarsfield Road
Watson Bondham Road Birchgrove Road
Weatherly Maley Lane Old Second Line Road
West Hunt Club Old Richmond Road Highway 416 IC 72
West Hunt Club Woodroffe Avenue Cleopatra Drive
West Hunt Club Woodroffe Avenue Lancelot Drive
Wilhaven Dunning Road Canaan Road
William Hodgins Vaughan Side Road Diamondview Road
William Mcewen Century Road W Cedarview Road
Woodroffe Bren-Maur Road Dead End
Wood'S Franktown Road Jock Trail
Worley Ormrod Road Flewellyn Road
Yorks Corners Mitch Owens Road Marionville Road

Wild Parsnip Strategy

The Public Works department has been proactively mapping out wild parsnip infestation levels across the city along roadsides, parkland and pathways. Each year, the wild parsnip infestation levels mapping is used to identify the control areas (roadside/parklands/pathways) for the upcoming year.

The integrated management strategy includes monitoring, mapping, the use of herbicides, mowing and evaluation. The herbicide Clearview was chosen in consultation with other Municipal and Provincial stakeholders and experts, and may impact other weeds/plants but should not impact trees or grass.  

Second year growth wild parsnip begins to dry up in August, so contact with the plant will be less likely to cause a reaction. However, the sap still remains inside the plant. Avoidance or personal protective gear, when handing the plant, is still recommended.

Wild parsnip (Pastinaca sativa)

Wild parsnip is an invasive plant that is increasingly common within the City of Ottawa in areas of uncultivated land, roadside ditches, nature trails, as well as on and surrounding rural and residential properties.

Wild parsnip may pose a health risk to humans. The plant sap contains chemicals that may cause skin and eye irritation and make the skin prone to burning and blistering when exposed to the sun. The blisters typically occur one to two days after contact with the plant. This can result in long-term scarring of the skin.

The best way to avoid contact with wild parsnip is to become familiar with what the plant looks like so you do not accidently come in contact with the plant. 


Wild parsnip is a highly branched plant, with hollow green stems. It has two growth stages: non-flowering leafy rosettes at ground level and 0.5 to 1.5 metre-tall flowering plants.

Early growth: In the first year of growth, low-growing non-flowering rosettes of leaves form with a cluster of spindly, compound leaves that resemble celery leaves.

In bloom: When wild parsnip is in bloom usually in the second and third year plants have tall, branched yellow flowering stalks that usually bloom in early June to late July.

Mature plant: Starting in August ‎the blooming plant will begin to turn brown and the leaves and stems will begin to dry up. This means that the toxic sap from the plant will also begin to dry up, and contact with the plant is less likely to cause a reaction. Once the plant is completely dry the seeds will fall to the ground.

Seeds are flat and round. It is a biennial plant, reproducing only by seed. The seeds can lie dormant for years making it even more challenging to control.

Low-growing non-flowering rosettes of early-growing wild parsnip
Early Growth

In bloom

Image of a mature wild parsnip plant
Mature Plant

Education and public awareness

How to avoid the plant

  •  It is recommended that the public stay on the groomed areas of parks, roadsides and pathways where there are less instances of wild parsnip.
  •  When working around wild parsnip or when walking through dense vegetation, wear goggles, gloves, long pants and long-sleeved shirts. Thoroughly wash boots and  gloves with soap and water before taking off your protective clothing.
  •  Children should be reminded not to pick wild flowers. Ensure children are able to identify wild parsnip in order to avoid exposure.
  •  If you are exposed to the plant sap, wash the contaminated area(s) thoroughly as soon as possible, and seek medical attention if skin irritation occurs.

Public education

Wild Parsnip Caution Sign
  • An awareness post card will be distributed at public events such as fall fairs. The awareness postcard will also be distributed to City partners such as school boards, and Ottawa Public Health.
  • Caution signs will been installed in areas where there are high levels of wild parsnip infestation. Staff will continue to install caution signs in areas where the public may reasonably expect to encounter wild parsnip, and the City encourages residents to be mindful of the plant when entering non-groomed portions of wooded and naturalized areas.
  • Hard copies of the postcard or flyer are available by contacting 3-1-1.
  • Staff will continue to work with Corporate Communications, Ottawa Public Health and other internal and external stakeholders to coordinate efforts related to health promotion and implementation of weed reduction strategies. Staff will also continue to make updates to the City’s website as they learn more about wild parsnip through the pilot project.
  • For additional information, please consult the City of Ottawa’s website. Residents can also contact the Ottawa Public Health Information Line for more information about the health impacts of wild parsnip at 613-580-6744.

Wild Parsnip look-a-likes

Giant Hogweed (Heracleum mantegazzianum)
Image of a giant Hogweed plant in full bloom

Photo courtesy of Ken Towle


  • 2.5 to 5 m high
  • Hollow, 5 to 15 cm thick
  • Prominent purple blotches
  • Distinct, coarse bristly hairs


  • Large, white umbrella-shaped clusters 30 to 90 cm across
  • Made up of 50 to 150 small clusters
Cow Parsnip (Heracleum maximum)
Image of a cow Parsnip plant

Photo courtesy of Lynda Shores


  • 1 to 2.5 m high
  • Hollow, 5 cm thick at base
  • Green, few to no purple spots
  • Soft and fuzzy hairs


  • White umbrella-shaped clusters
  • 10 to 30cm across, made up of 15 to 30 small clusters
Queen Anne's Lace (Daucus carota)
Image of Queen Anne's Lace

Photo courtesy of Chris Evans, Illinois Wildlife Action Plan


  • 0.3 to 1.5 m high
  • Green, 1 to 2.5 cm thick
  • Covered with fine bristly hairs


  • White flower cluster 5 to 10 cm across
  • Pale pink before fully opened
  • Often single purple flower in centre of cluster
Angelica (Angelica spp.)
Image of an Angelica plant - greenish-white globe-like flower clusters

Photo courtesy of Owen Williams


  • 1.2 to 2.1 m high
  • Purple or purple blotched
  • Smooth (no hairs)


  • Greenish-white globe-like flower clusters
  • 8 to 25 cm across

On private property 

Strategies to remove wild parsnip include the digging out the plant roots, targeted mowing, the use of herbicides and ongoing monitoring.

Digging the root up: Residents that have a small infestation in a yard or garden (fewer than 100 plants) or who do not want to use pesticides can dig out as much of the taproot as possible with a sharp shovel or spade. Follow-up digging will be required every few weeks to deal with re-growth (if the taproot was not completely removed) or missed plants. DO NOT burn or compost wild parsnip plants that have been cut down or dug up. Plants and roots that have been removed should be placed in a dark plastic bag and placed in the sun if possible away from areas children or pets could access them. After the wild parsnip plant has been left in a black bag for one to two weeks in the sun, it can be collected through your normal waste collection as garbage, not as leaf or yard waste. The bags do not need to be labelled. The City is handling wild parsnip in accordance with the requirements of the Ministry of Environment.

Targeted mowing: Mowing can be effective if begun just after peak blooming, but before the seeds set in the late summer or early fall. Cut plants will likely re-sprout after mowing, so it is important to combine mowing with other control methods such as bagging and removing the plants, especially those that are flowering and spot spraying with an approved herbicide. Be especially careful when using mowers, weed whips, mechanical string trimmers as they can spray users with sap and bits of the plants, leading to redness and sometimes hundreds of blisters on exposed skin. Wear goggles and protective clothing when mowing.

Use of herbicides: When a weed such as wild parsnip is declared a noxious weed, both the City and residents are able to purchase herbicides to control it. This is not considered a cosmetic use of pesticides because this plant can pose a risk to people. For more information please go to the Ontario Ministry of the Environment, Conservation and Parks (MECP) website.

Monitoring: Long-term monitoring is important in keeping this weed under control, as seeds will continue to germinate for several years.

Other information

Reporting wild parsnip: Report wild parsnip, poison ivy or giant hogweed on city property by calling 3-1-1 or by reporting online.

Safety information: Important safety information on wild parsnip hazards, control and disposal is available on the Ontario’s Invading Species Awareness Program web site

Agricultural and Rural Affairs Committee Reports: March 3, 2016 Wild Parsnip Strategy

Education: The City of Ottawa has produced an informational postcard and factsheet that are available upon request. Please contact to request copies. Supplies may be limited.

Giant hogweed


Giant Hogweed is a serious invasive plant that poses a moderate threat to human health and safety. Giant Hogweed is primarily found along roads, streams and open areas. Plants reproduce well on disturbed sites, and prefer full sun and open habitat common along roadsides and ditches in rural areas.

This plant is poisonous. Hollow stem, leaves and plant hairs produce a sap if broken. Sap can cause serious skin inflammation on contact. If contaminated skin is exposed to sunlight a more serious reaction can occur including blisters, discolouration, and scars. If sap has contact with eyes, loss of vision, blindness or damage to eyes can occur.


Giant Hogweed flowers from June to August with white (sometimes pinkish) flowers in large clusters. It is often confused with several other plants which pose no health risk such as cow parsnip (1-2 m in height, fine hairs on stem creating fuzzy appearance, leaf less deeply cut and smaller with small hairs and flowers in more rounded clusters no more than 30 cm across); Angelica (1-3 m in height, smooth green-purple stem with no hairs, small leaflets no more than 60 cm, flowers rounded in softball-sized clusters up to 30 cm across).

It is a long-lived perennial plant and can take 3 to 4 years before it flowers only once. It can range in height from 1 to 5.5 metres. Plants produce huge leaves that are up to 1 metre in width. Leaves are deeply cut, with large lobes, and sharp teeth on all leaf margins.

It has sharp pointed bumps on stems and leaf petioles. Stems have reddish purple flecks and are often entirely purple at the base, mostly hollow and up to 10 cm in diameter. Stems and petioles are densely hairy.

Giant Hogweed

How to Avoid Giant Hogweed Burns

• When working around Giant Hogweed or when walking through dense vegetation, wear goggles, gloves, long pants and long-sleeved shirts. Thoroughly wash boots and  gloves with soap and water before taking off your protective clothing.
• Children should be reminded not to pick wild flowers. Ensure children are able to identify Giant Hogweed in order to avoid exposure.
• If contact with skin occurs, avoid exposure to sunlight and wash immediately.
• If a skin reaction occurs, seek medical attention.

 Important safety information on Giant Hogweed hazards, control and disposal is available on the Ontario’s Invading Species Awareness Program web site

On private property

In the spring (early May), use a spade to remove as much of the root as possible. You may need to dig repeatedly to remove it completely.

In the summer (early July), remove plants without flowers by digging the stems and roots out and dry them thoroughly before disposing of them. To prevent seeds from growing and spreading, remove any flower heads before they ripen (when they are white).

On city property

Report Giant Hogweed, Wild Parsnip, and Poison Ivy on city property by calling 3-1-1 or letting us know with this on-line reporting form. Or call 3-1-1.  

To assist with controlling the spread of many harmful and invasive plants on city property, the City cuts the roadside grass throughout the summer months. Each rural roadside receives an average of two full cutting cycles and each suburban and urban roadside receives an average of six full cutting cycles.

If grass cutting does not successfully control these weeds and they still pose a public safety hazard, the City may choose to use herbicides. . . Herbicides are used in accordance with the provisions of the Ontario Pesticide Act, and may only be applied by a licensed applicator. The City will always post highly visible signs in the general area if an herbicide is used before it is applied and the sign will stay up for 2 days afterwards in compliance with provincial requirements. The name of the herbicide used along with the name and phone number of a person who can answer questions about the application is always written on these signs.

Poison ivy

Poison Ivy is a harmful weed that is commonly found within the City of Ottawa in areas of uncultivated land, roadside ditches, nature trails, woodlots as well as on and surrounding rural and residential properties.

Poison Ivy may pose a health risk to humans. All parts of the plant contain a poisonous substance (urushiol) which causes an irritating inflammation of the skin, frequently developing blisters. About 50-60% of people are allergic to this substance.

The best way to avoid contact with Poison Ivy is to become familiar with what the plant looks like and stay away from it.


Poison Ivy can be found in clusters of three leaflets. Each leaflet grows on its own stem and connects to the main stem. Poison Ivy leaves and stems do not have thorns.  

Poison Ivy

How to Avoid Poison Ivy Rash

  • When working around Poison Ivy or when walking through dense vegetation, wear goggles, gloves, long pants and long-sleeved shirts. Thoroughly wash boots and gloves with soap and water before taking off your protective clothing.
  • Children should be reminded not to pick wild flowers. Ensure children are able to identify Poison Ivy in order to avoid exposure.
  • If you are exposed to the plant, wash the contaminated area(s) thoroughly as soon as possible, and seek medical attention if skin irritation occurs.

Removing Poison Ivy from your property:

Poison Ivy is mainly spread by soil movement and contaminated equipment, but can still be found in private gardens. Minimizing soil movement and regular equipment washing can help prevent new introductions. Poison Ivy can be controlled by digging out the roots and stems as well as by the use of certain herbicides (chemical weed-killers). For more information on important safety, control and disposal methods, visit the Ontario Ministry of Agriculture, Food and Rural Affairs web site.

On City Property

Report, Poison Ivy, Wild Parsnip or Giant Hogweed on city property by calling 3-1-1 or let us know with this on-line reporting form. Or call 311.

Although noxious weeds generally establish themselves in areas of uncultivated or untraveled lands, there are circumstances where they may be found near travelled areas of City property such as parks and pathways.

To assist with controlling the spread of many harmful and invasive plants on city property, the City cuts the roadside grass throughout the summer months. Each rural roadside receives an average of two full cutting cycles and each suburban and urban roadside receives an average of six full cutting cycles.

If grass cutting does not successfully control these weeds and they still pose a public safety hazard, the City may choose to use herbicides. . . Herbicides are used in accordance with the provisions of the Ontario Pesticide Act, and may only be applied by a licensed applicator. The City will always post highly visible signs in the general area if an herbicide is used before it is applied and the sign will stay up for 2 days afterwards in compliance with provincial requirements. The name of the herbicide used along with the name and and phone number of a person who can answer questions about the application is always written on these signs. 

About the Emerald Ash Borer

The Canadian Food Inspection Agency has issued a ministerial order to prohibit movement of firewood, and ash-tree products such as nursery stock, logs, branches and wood chips from areas of Ottawa and Gatineau to any other surrounding regions to limit the spread of Emerald Ash Borer (EAB).

Une photo en gros plan de l'agrile du frêne

Emerald Ash Borer is a non-native, highly destructive wood-boring beetle that feeds under the bark of ash trees. All species of ash are susceptible to attack, except mountain ash, which is not a true ash species. Since it was first identified in Michigan in 2002, EAB has killed millions of ash trees in Ontario and many parts of the United States. It poses a major economic and environmental threat to urban and forested areas. It was confirmed in Ottawa in 2008 and its impacts can be clearly seen spreading from the St. Laurent area. Since the insect spends most of its lifecycle under the bark of trees, it can be easily moved with firewood or other tree materials such as nursery stock, logs, brush and larger wood chips. This insect is able to fly, but since its spread has been primarily along major highways and transport routes, it is clear that humans are the main vector of dispersal.

What EAB does

Emerald Ash Borers normally have a one-year life cycle, but some can take up to two years to mature. EAB lays eggs on tree bark and in bark crevices starting in late May.

In its larva form, which resembles a caterpillar, Emerald Ash Borer feeds just under the bark of ash trees. This feeding disrupts the tree’s circulation of water and nutrients. The presence of even a few insects in a tree can kill it.

Top branches of ash trees usually die off first. Trees can lose half its branches in a single year. Once larvae finish feeding under the bark, they mature into adult beetles that chew their way out of the tree.

ainures en forme de «S» et trous en forme de «D» de 3,5 à 4 mm causés par les coléoptères adultes. Photo gracieuse eté de Troy Kimoto, ACIA.

S-shaped grooves and D-shaped exit holes 3.5 – 4 mm wide caused by adult beetles photo courtesy Troy Kimoto, CFIA

  • look for loss of leaves and dead branches in the upper part of ash trees
  • unusually thin tree crowns
  • branch and leaf growth in the lower part of the stem where growth was not present before
  • unusually high woodpecker activity
  • look for bark splitting, S-shaped grooves beneath the bark caused by larval feeding, and D-shaped
  • exit holes 3.5 – 4 mm wide caused by adult beetles

Infested ash trees in North America generally die after two to three years, but heavily infested trees have been observed to die after one year.

Ash trees

Learn how you can identify Ash trees.

The City of Ottawa's Emerald Ash Borer Strategy

The City's Emerald Ash Borer (EAB) strategy includes treating trees with TreeAzinTM, removing and replanting trees, proactive plantings, as well as public education to raise awareness regarding EAB and proper wood handling and disposal.

Selective tree injections 

The City is treating selected ash trees throughout the Ottawa region with TreeAzinTM. TreeAzinTM is a systemic insecticide produced from extracts of Neem Tree seeds (Azadiracta indica).  It is injected under a tree’s bark, directly into the conductive tissues, and moves upwards with the flow of water and nutrients.  TreeAzinTM can be very effective at controlling EAB infestations but injections are required every two years and treatment does not ensure tree survival.  For more information on TreeAzinTM, please visit the manufacturer’s website at

Because of the large population of ash trees in Ottawa, it would be prohibitively expensive to inject every ash tree on city property. The City’s injection program, therefore, focuses on injecting ash trees that will receive the most benefit. The City’s injection policy aims to:

  • Protect a mix of age classes to ensure diversity in the population of protected ash trees, and
  • Provide ash tree protection in neighbourhoods with a high percentage of forest cover from ash species

Trees are assessed on an individual basis and considered for injection based on a number of factors including tree health, tree form and tree location.

Are you thinking of having your privately-owned ash tree injected?

Treating your ash tree can be a good investment when taking into account the cost for tree removal and replanting as well as the benefits urban trees provide including increased property value and energy savings.

Slow down the spread

Residents can help by:

  • Learning to identify EAB and ash trees
  • Reporting suspected outbreaks
  • Not moving firewood out of Ottawa and Gatineau or into adjacent communities 
  • Being aware of regulations for firewood and ash products 
  • Not bring firewood to your cottage or campsites 
  • Buying your firewood locally and know where your firewood originates 
  • Obeying all ministerial orders issued by the federal government 
  • Remembering, even after an infested tree has been cut down, EAB continues to live in the wood

Failure to obey a ministerial order can further put our forests at risk, and could also lead to prosecution and fines as high as $50,000.

Removal and disposal

The City is responsible for maintaining or removing City-owned ash trees (in City road allowances, municipal parks and natural areas). Trees will only be removed if they are highly infested with the Emerald Ash Borer (EAB) or if they become structurally unstable.

Private property owners are responsible for removing and disposing of affected ash trees on their properties. It is recommended that the owner use a certified arborist and ensure full compliance with the ministerial order for wood movement and disposal.

Home owners are still able to put leaves and branches under four inches in diameter and four feet in length out for curbside leaf and yard waste collection even if they are from ash trees. Residents can continue to bring their own leaf and yard waste to the Trail Waste Facility for free if it meets the above requirements. A fee will apply to contractors and residents bringing in material greater than four inches in diameter

Don’t move firewood

The human movement of infested materials such as firewood, logs, branches, nursery stock, chips or other ash wood is the most common way EAB has been spread. Adult Emerald Ash Borer can fly, but research indicates adults usually fly a short distance upon emergence. The City of Ottawa and the CFIA are asking the public not to move firewood or other wood materials. To reduce the risk of spreading forest pests, buy and burn firewood locally.

You can help by learning to identify EAB and ash trees and by reporting suspected outbreaks of the Emerald Ash Borer by contacting the CFIA at 1-866-463-6017 or e-mailing the City For more information see the Ontario Ministry of Natural Resources’ EAB Site.