What Makes a Plant Native to Ontario?

A guide to what it really means for a plant to be native to Ontario

For gardeners, understanding what qualifies as a native plant helps support pollinators, improve biodiversity, and build landscapes that are better adapted to Ontario’s climate. While the term “native plant” is widely used in gardening and landscaping, it is often misunderstood. The sections below explain what the label actually means and how it applies to plants grown in Ontario gardens.

1. Does "Native to Ontario" Mean Originated Here or Just Grows Here?

This is one of the most common points of confusion in native plant gardening, and the distinction matters.

A plant that is native to Ontario is not simply one that can grow and survive here. It is one that evolved and developed in this region without human introduction.

Botanists and ecologists generally define a native plant as a species that was present in a region prior to large-scale European colonization, typically before the 1500s in Ontario. These plants developed alongside the local soils, climate, insects, birds, and fungi over thousands of years, forming deeply embedded ecological relationships.

A native oak, for example, supports hundreds of caterpillar species that have co-evolved with it. These are relationships that a non-native tree, no matter how well it grows here, cannot fully replicate.

By contrast, a plant that merely grows well in Ontario, tolerating our winters, soils, and moisture conditions, is better described as adaptable, hardy, or naturalized. Many invasive species fall into this category. They thrive here without being native and often outcompete the plants that actually belong.

Some commonly planted garden species that are often mistaken for native plants include:

Norway Maple (Acer platanoides)
Widely planted across Ontario and extremely hardy, but native to Europe and invasive in many Ontario woodlands.

Burning Bush (Euonymus alatus)
A popular ornamental shrub that survives Ontario winters but originates from Asia.

Purple Loosestrife (Lythrum salicaria)
Naturalizes aggressively in Ontario wetlands but is a European native and a serious ecological threat.

The bottom line is simple: if a plant was introduced here by humans, whether intentionally through horticulture or accidentally through trade, it is not native to Ontario regardless of how well it grows.

2. How Far Back Does "Native" Go? Does It Mean a Plant Was Always Here?

The honest answer is no. Native to Ontario does not mean a plant has been here since the beginning of time. Ontario's landscape has changed dramatically over geological history, most recently due to glaciation.

The Post-Glacial Reality

As recently as 10,000 to 12,000 years ago, most of Ontario was buried under the Laurentide Ice Sheet, which in some places reached depths of more than two kilometres. There were no forests, meadows, or wetlands. The landscape was almost entirely ice.

As the glaciers retreated, plants gradually migrated northward from refugia, which were ice-free areas to the south and southeast. Over thousands of years they colonized bare rock and mineral soils, slowly forming the ecosystems we recognize today.

This means that every plant we consider native to Ontario today arrived here at some point after the glaciers retreated. Some species colonized quickly while others took thousands of years to establish.

Southern Ontario's Carolinian zone, for example, supports species that expanded northward as the climate warmed after glacial retreat. Some of those warm-adapted species are now again under pressure as the climate continues to shift.

What Timeframe Defines Native?

The most widely accepted benchmark is pre-European contact, roughly before the 1500s. This baseline is used by organizations such as the Ontario Wildflower Project, the North American Native Plant Society, and government agencies including the Ontario Ministry of Natural Resources.

The reasoning is that before large-scale European settlement, plant communities in Ontario had reached a relatively stable equilibrium shaped by Indigenous land stewardship, natural disturbance cycles, and thousands of years of ecological co-evolution.

Anything introduced after that period, whether in the 1600s or the 2000s, is considered non-native, introduced, or exotic even if it has been present for several centuries.

3. Are Weeds and Ornamental Plants Given the Native Label?

Weeds

Some weeds are Ontario natives and some are not. The term "weed" is a cultural judgment rather than a botanical one.

A weed is simply a plant growing where humans do not want it.

Many of Ontario's most ecologically valuable native plants are sometimes dismissed as weeds.

Common Milkweed (Asclepias syriaca)
Essential for Monarch butterfly reproduction, native to Ontario, and often removed as a roadside nuisance.

Wild Bergamot (Monarda fistulosa)
A native pollinator plant that spreads readily and may appear as an unwanted volunteer in gardens.

Goldenrod (Solidago species)
One of the most important late-season food sources for pollinators. It is frequently blamed for hay fever even though ragweed is the actual cause.

On the other hand, many plants widely recognized as weeds in Ontario are not native at all.

Dandelion (Taraxacum officinale), Common Chickweed (Stellaria media), and Garlic Mustard (Alliaria petiolata) were all introduced from Europe. Garlic Mustard in particular is a serious invasive species that disrupts mycorrhizal networks in Ontario forests.

Weed status and native status are completely independent. A plant can be native and weedy, native and well behaved, non-native and invasive, or non-native and garden-friendly.

Ornamental Plants

Many Ontario native plants have been developed into cultivated ornamental varieties for the horticultural trade, which introduces some nuance.

A straight-species native plant, such as Monarda fistulosa grown from regional seed stock, carries the full ecological value of its native status. However, an ornamental cultivar derived from a native species occupies a more complicated middle ground.

Many popular ornamental plants commonly sold in Ontario nurseries are not native at all, even if they have been grown here for generations. Examples include:

• Lilac (Syringa vulgaris)
• Most garden roses
• Forsythia
• Butterfly Bush (Buddleja davidii)
• Most ornamental grasses used in landscaping

These plants may be beautiful and useful in gardens, but they do not carry the ecological relationships associated with native species.

4. Can New Plant Varieties Be Labeled as Ontario Native?

This question is actively debated in horticulture and conservation circles.

The short answer is that new cultivars and hybrids of Ontario native species cannot accurately be labeled as Ontario Native, and doing so is considered misleading by many ecologists and native plant organizations.

Why Cultivars Do Not Qualify

When a native plant species is selected, bred, or hybridized to produce a cultivar, the result may resemble the original plant but it has been genetically altered through human selection.

Common alterations include:

• Double or sterile flower forms that produce little or no nectar or pollen
• Altered leaf pigmentation that may affect insect recognition
• Compact or dwarf growth habits that change ecological function
• Hybridization with non-native species

Research from the Tallamy Lab at the University of Delaware and others has shown that some native cultivars support significantly fewer insects than their straight-species counterparts, particularly specialist bees and caterpillars that rely on specific plant traits.

The "Nativar" Debate

The horticultural industry often uses the term nativar, meaning a cultivar derived from a native plant.

Some organizations take a pragmatic position and consider nativars preferable to completely non-native species. Others argue that cultivars should never be labeled as native plants because they can mislead gardeners seeking genuine ecological impact.

A practical standard is to reserve the Ontario Native label for straight species that occur naturally in Ontario. Cultivars and hybrids may reference their native parentage but should not carry the Ontario Native label outright.

Regional Ecotypes

Even within straight species, regional genetics can matter.

For example, Swamp Milkweed (Asclepias incarnata) grown from seeds sourced in Georgia is the same species as one from Huron County, but it may be adapted to different daylight cycles, frost timing, and climate conditions.

For restoration projects and ecological plantings, Ontario-sourced seed stock is generally preferred.

5. Ontario's Most Popular Native Plants

Ontario's native flora spans several ecological zones, from the Carolinian forests of the southwest to the boreal woodlands of the north.

The plants below represent some of the most widely grown and ecologically valuable native plants commonly available for gardens in southern and central Ontario.

Common Name	Scientific Name	Plant Type
Eastern Redbud	Cercis canadensis	Tree
Sugar Maple	Acer saccharum	Tree
Red Osier Dogwood	Cornus sericea	Shrub
Buttonbush	Cephalanthus occidentalis	Shrub
Wild Columbine	Aquilegia canadensis	Perennial
Common Milkweed	Asclepias syriaca	Perennial
Swamp Milkweed	Asclepias incarnata	Perennial
Black-eyed Susan	Rudbeckia hirta	Perennial
Wild Bergamot	Monarda fistulosa	Perennial
Joe-Pye Weed	Eutrochium maculatum	Perennial
Great Blue Lobelia	Lobelia siphilitica	Perennial
Canada Goldenrod	Solidago canadensis	Perennial
New England Aster	Symphyotrichum novae-angliae	Perennial
Ostrich Fern	Matteuccia struthiopteris	Fern
Wild Ginger	Asarum canadense	Groundcover
Virginia Creeper	Parthenocissus quinquefolia	Vine
Canada Wild Rye	Elymus canadensis	Grass
Prairie Dropseed	Sporobolus heterolepis	Grass
Little Bluestem	Schizachyrium scoparium	Grass
Pennsylvania Sedge	Carex pensylvanica	Sedge

 

This list represents only a small portion of Ontario's native flora, which includes thousands of species across trees, shrubs, perennials, grasses, sedges, ferns, and aquatic plants.

The most ecologically impactful native gardens include plants from multiple layers of the landscape, including canopy trees, understory shrubs, herbaceous perennials, and ground-layer plants.

A Note on Labeling Standards

There is currently no regulated legal definition for the term Ontario Native within the horticultural trade.

As a result, accurate labeling often depends on the integrity of growers and retailers.

The standard adopted by many conservation organizations is straightforward: a plant qualifies as Ontario Native if it is a straight species that existed in Ontario prior to European colonization, is not a cultivar or hybrid, and ideally originates from regional Ontario seed stock.

Final Thoughts

Native plants are not just a conservation concept. They are often among the most resilient and rewarding plants to grow in Ontario landscapes.

By choosing true native species whenever possible, gardeners can create landscapes that are beautiful, ecologically functional, and deeply connected to the natural history of this region.