Cathy Kavassalis – July 8, 2026

Preventing the spread of invasive plants begins in your garden. Don’t buy, plant, or share invasive plants, and dispose of any plants you remove carefully so they cannot re-establish or spread. Learning to recognize invasive plants is the first step in managing a global problem.

Learning how to remove or manage invasive plants in your home garden is the next step. New or small infestations can often be controlled by hand-pulling or digging; established populations take patience, persistence, and a combination of methods. Whatever you do, the goal is the same: keep seeds, roots, rhizomes, and fragments from spreading. And share what you learn with your neighbours, because invasive plants don’t respect fences.

1. Prevent introductions

1. Check before you buy or share. Many invasive plants are still sold or passed between gardeners. Research a plant before you plant or share it, and check whether it’s known to cause harm.
2. Buy clean soil, mulch, and compost from reputable sources; contaminated material can carry seeds and root fragments.
3. Don’t move soil or share plants from an infested bed. Root-wash anything you do move, because one fragment or seed can start a new infestation.
4. Clean tools, boots, and equipment between areas; fragments and seeds are a major spread pathway.
5. Work with your neighbours to prevent and control spread.

2. Identify potential problems – What’s that plant?

• If a plant appears in your garden, or you don’t know what you are growing, you can use apps like Google Lens, iNaturalist, and Pl@ntNet to give you possible suggestions. These are not 100% accurate and results should be double-checked.
• Confirm with reliable sources: government sites (.gc.ca, .on.ca), universities, botanical gardens, conservation trusts, and organizations like the Ontario Invasive Plant Council.
• Field guides help too.
• When in doubt, ask a local Master Gardener (mgoi.ca) or other expert to confirm.

3. Is it an invasive plant?

Search a plant’s scientific name together with the word “invasive” to check whether it is invasive. This isn’t entirely reliable, as older gardening sites may not be up to date with current lists, but it is a start.

Many plants can potentially harm Canada’s economy, environment, and public health. Some are regulated federally like giant reed grass (Arundo donax) as a pest plant under the Plant Protection Act, or ox-eye daisy (Leucanthemum vulgare) under the Seeds Act (Weed Seeds Order). Some are regulated provincially like Japanese knotweed (Reynoutria japonica) under the Ontario Invasive Species Act, or wild chervil (Anthriscus sylvestris) under the Weed Control Act (see attached list).

Many others are widely recognized as harmful by scientists and conservation organizations yet are still sold in nurseries, like goutweed (Aegopodium podagraria), Japanese barberry (Berberis thunbergii), and burning bush (Euonymus alatus). Ontario’s 2022 Auditor General report identified many common invasive plant species shared by gardeners and sold in nurseries like English ivy (Hedera spp.) and periwinkle (Vinca minor) and recommended we work to prevent their spread. (That list of common, easy-to-spot invasive plants is attached.)

The Society for Ecological Restoration Ontario (SERO) has published an Invasive Exotic Plant Species Ranking for Southern Ontario (2025), identifying plants currently affecting natural areas and prioritizing their removal based on their potential impact. The Ontario Invasive Plant Council lists invasive species for which it has developed Best Management Practices (BMPs), along with other Resources. The Midwest Invasive Plant Network’s has compiled al Midwest Invasive Plant List that includes over 450 plants now considered invasive, noxious, or pests by one or more jurisdictions across its region, which includes Ontario. Visit CCIPR.ca for more lists. Ask a Master Gardener if you are unsure.

4. Size up the situation

Once you have identified a potentially invasive plant, you need to answer several questions. Is it a woody plant (a shrub or tree) or is it herbaceous (dies back in winter)? How much is there, and where is it growing? Is it in the lawn, under trees, among perennials? Near a natural area, woodland, or meadow? In or near a pond, stream, or lake? Plants near water or natural areas carry higher stakes, because seeds and fragments travel far beyond your property. Answers to these questions help you identify the right tools and help to prioritize your efforts.

Examples

• Tailor your action to the plant. Understand its life cycle and how it spreads. The key is to prevent the production of seeds, and/or to starve and remove the roots. Proper timing can minimize your effort and the need to repeat. While each plant has its own optimal management regime, here are some examples.

WEED SEEDLINGS: the best case is to catch it early

• A handful of seedlings or a small first-year patch is the easiest and cheapest stage to deal with. Hand-pull when the soil is moist, removing roots, or use a scuffle hoe on seedlings to sever weeds just below the soil surface. Mulch or replant the gap and check back throughout the season. No other action is needed.

HEAVY SEEDERS — stop the seeds, stop the spread: example garlic mustard

• For invasive plants that spread primarily by seed, success means preventing seed production. Garlic mustard is a good example. This biennial can produce anywhere from 100 to 10,000 seeds in its second year before naturally dying.

• Scout for and remove first-year rosettes whenever possible. Second-year plants can also be pulled but allowing them to bolt and then cutting the flowering stalk at the base is recommended, because it minimizes soil disturbance and reduces germination of buried seeds. Carefully bag and dispose of flowers or developing seed heads, as they may continue to mature after removal. Monitor for regrowth, as additional flowering stalks can sometimes be produced.

• Because garlic mustard seeds can remain viable in the soil for several years, expect to return each spring to remove new seedlings and flowering plants until the seed bank is exhausted. Replanting disturbed areas with desirable vegetation can help limit reinvasion by reducing opportunities for new seedlings to establish.

• Should garlic mustard densely cover large areas, new research suggests that land managers should prioritize edge populations. After a decade or more, garlic mustard populations appear to decline, so the multiyear effort required to remove and restore is not always merited. Learn more: MIPN GM Management Decision Tree.

DEEP ROOTS — contain and manage: example creeping bellflower

• Creeping bellflower (Campanula rapunculoides) is a very difficult plant to eradicate. Brittle taproots can extend more than 30 cm deep, while extensive creeping lateral roots (rhizomes) periodically produce additional taproots and rhizomes. Roots fragment easily, and even small pieces left behind can resprout.

• Where digging is an option, remove as much of the root system as possible and sift the soil for root fragments. A coarse soil sieve can be helpful. When the plant is intertwined with the roots of shrubs and trees, repeated cutting of top growth at the soil surface can help prevent it from replenishing its underground reserves.

• Contact herbicides, selective lawn herbicides, and occasional pulling often provide disappointing results because the plant readily regenerates from its extensive root system. Long-term success depends on exhausting underground reserves through repeated removal of top growth, careful digging, or prolonged exclusion of light.

• For large patches (where desirable plants can be root-washed and temporarily transplanted elsewhere), cover the area with an opaque tarp or a thick layer of mulch to exclude light. However, creeping bellflower can remain dormant for two or more years, so patience and monitoring are essential.

• In perennial borders, where the plant is intertwined with shrub and tree roots, complete removal may not be practical. In these situations, focus on preventing flowering and seed production, containing the infestation, and gradually weakening the root system over several seasons by continually cutting top growth.

• Dispose of all removed plant material in sealed bags and place it directly in the garbage. Do not compost this species.

WOODY SHRUBS & SMALL TREES: stop them while they are young; cut and cover: example common buckthorn

• Many woody invasive plants sucker profusely. Buckthorn is a key example: when cut, it resprouts vigorously. Seedlings and small saplings (up to about finger-thickness) can often be pulled by hand, ideally after rain when the soil is moist. For thicker stems (up to around 8 cm/3 inches), a lever tool such as a weed wrench, Extractigator, Pullerbear, or Uprooter can be used to pull them out, roots and all.

• For larger shrubs or small trees, cut the trunk as close to the ground as possible, tightly cover the stump with a thick light-blocking black bag, and secure it with a zip tie so it rests flat on the ground. Leave it in place for at least two growing seasons, checking that no shoots escape. (Check with your municipality whether removal of large trees is permitted.)

• Brushing cut stumps with a systemic herbicide like glyphosate is effective, but glyphosate is restricted under Ontario’s Cosmetic Pesticide Ban: it is generally a job for a licensed exterminator and is available to a homeowner only where a specific exception to the ban applies (see the section on herbicides and permits below). Note that municipal permission may also be required to remove a tree.

• Where removal is difficult, try to bag the berries to limit bird-spread seed, and expect to scuffle or pull seedlings for several years.

AQUATICS: For aquatic invader near or in water — caution and care is needed: example yellow flag iris

• This is the higher-stakes case, so identify carefully first: yellow flag iris looks like our native blue flag iris when it isn’t in bloom. Yellow flowers mean the invader; blue-purple flowers mean leave it alone.

• Yellow flag iris spreads by floating seeds and by rhizome fragments, so the overriding rule is to keep every piece and seed out of the water. Dig out small clumps, removing as much rhizome as you can, and wear gloves and eye protection, as the sap can irritate skin. Bag everything (never compost it or leave it near the shoreline) and replant with natives like blue flag iris or other native aquatic species (check with your local conservation authority or watershed managers for recommendations).

• For larger stands, or anything in flowing water, this may be beyond a do-it-yourself fix: herbicide use in or near water is tightly restricted, so report the infestation (Invading Species Hotline 1-800-563-7711, EDDMapS, or iNaturalist) and contact your conservation authority or a professional.

Don’t plant it; don’t share it. Call for it to be regulated because it is still widely sold for ponds.

KNOTWEED: For big trouble — herbicides may be required: example invasive knotweeds

• Japanese knotweed (Reynoutria japonica), Giant knotweed (Reynoutria sachalinensis), Bohemian knotweed (Reynoutria × bohemica), Himalayan knotweed (Koenigia polystachya) are all regulated species.

• Invasive knotweeds are prohibited to sell or share in Ontario. Unfortunately, many are well established in gardens and they are widely spreading along transportation corridors. Should plants appear in your garden, promptly dig them out.

• While small infestations can be removed by hand, larger established stands may take years to remove. For large infestations, start at the edges and work inward. While there are sterile cultivars of Japanese knotweed that primarily spread by aggressive roots, others spread by seed. It is important to remove fertile seed heads before they are released. Prioritize any knotweed near watercourses, where they are particularly harmful.

• Mowing or cutting knotweed causes it to send out lateral roots and causes it to spread more rapidly and widely so cut with caution. Vigilant cutting to the ground can starve the roots but must be done weekly for an extended period of time.

• While tarping can be used, this is a multiyear process. Research suggests that stands cut below or at soil and tarped with thick black plastic (7-mil or thicker) for at least five years, can be eliminated. This is a lengthy process and it is not ideal for the environment to cover an area for such extended periods.

• Authorities agree chemical control is the most effective approach for managing large or well-established knotweed stands. Experts recommend glyphosate. It is best applied to the foliage four to six weeks before first frost (wetting both sides of the leaves) when the plants are most likely to draw the herbicide into their root system. Leaves should begin yellowing in a few days. Reapply in two weeks if healthy foliage remains. Several years of treatment is often required.

• Under the Cosmetic Pesticide Law, this herbicide may be used by licensed professionals and homeowners under exceptions for public health and safety (e.g., plants poisonous to humans by touch and plants that affect public works and other buildings and structures) and for the management and protection of natural areas. The latter requires a letter from either the Ministry of Natural Resources and Forestry (MNRF) or the Ministry of the Environment, Conservation and Parks (MECP) and/or others. See our MGOI Knotweed Factsheet for more information.

Homeowners should request clearer exemptions and guidance from the MECP for the control of invasive species.