Can Native Plants be Invasive? Explaining Common Plant Terms.
Plenty of confusion and many misused terms get thrown around in gardening forums, Facebook groups and general conversations when discussing plants. This occurs even more when native plants are concerned. We get to the bottom of common terms such as invasive and aggressive, which will allow you to garden more confidently, when selecting plants for your space.
Can a native plant be invasive?
A native plant will never be invasive.
A native plant can be aggressive.
A native plant can be deemed a weed.
An invasive plant can be deemed a weed.
An introduced plant can become invasive. Even after years of playing nicely in its new home, climate change or the alteration of competitive species (pests or plants) can change how a plant behaves in an ecoregion.
Let’s dive into each term in more detail so that you can better understand how they apply to your garden and the surrounding ecosystem
Why do the terms we use to describe plants matter?
Introduced. Invasive. Aggressive. Weed.
These terms tend to bring negative images to our minds when we discuss them in the context of gardening. The words associated with plants can leave a longer impression on a gardener then the experience of the plant or the name of the plant. Once ‘weed’ is associated with a plant our brains automatically place it into a ‘bad’ category.
These terms become incredibly important in restoring balance to ecoregions and supporting native plants and native species. Vague lawmaking terms can be used to harass residents and food growers threatening self-sufficiency.
A recent example of where this matters in policy making is the Toronto Natural Garden Exemption by-law. The removal of the application may appear as progress, but without the protection of this exemption, residents can pick on and harass a neighbour that has decided to restore their property to a native habitat that does not reflect current residential expectations. A by-law officer does not have clear plant lists to determine what is a ‘weed’ and what is acceptable.
Plants, like children are inherently good. Placed in the wrong setting or without proper boundaries and checks, trouble can occur. This does not make a plant bad. But it may perform harmful actions in this setting and may require intervention (removal).
In conscious parenting practices, caregivers focus on their own language surrounding children’s behaviour. We avoid labelling children and instead label their actions. Plants can, and should be treated the same way.
What is a native plant?
A plant that occurs naturally in an ecoregion without any human interventions.
It can often be challenging to determine what is a true native as humans regularly brought crops, seeds, and plant material with them when they travelled to, or explored new regions. The impact of humans on an ecoregion goes back centuries to times when documentation of the existing habitat may not be readily available.
What is an introduced plant?
A plant that is non-native to the ecoregion.
The majority of gardens and nursery stock available falls under this category. Many plants have been collected and distributed from other regions of the globe. Often selected for their showy appearance, resilience, nutrition or cultural significance, the reasons for why they are here are plentiful.
The majority our food crops, fall into this category.
Examples of introduced plants are magnolia trees, tulips, hydrangeas, boxwoods etc.
What is an invasive plant?
A plant that is non-native to the ecoregion, whose presence causes harm to or poses a threat to environmental health.
Examples of invasive plants are dog strangling vine, garlic mustard, phragmites etc. The full, government recognized, list of Ontario invasive plants can be found here.
There are many plants that the government has not formally recognized yet that display invasive habits. Often the plants that threaten the economy, specifically agricultural crops, take priority. There are many that have escaped their original introduced zones and alter or out-compete native plant species. Examples of these are scilla, dandelions, burning bush, goutweed, periwinkle etc.
Invasive plants can escape their human-intended locations through seed distribution (wind, birds, ants), rhizomes etc. Even though you may have never noticed your burning bush sprouting up elsewhere in your yard, the seeds from your shrub get carried by birds into the ravine and forested regions and spread.
What is a weed?
A plant in the wrong place as per human opinion.
Many native plants are considered weeds. Native plants are well suited and thrive in their ecoregions and may pose competition to our cultivated, introduced plants.
A weed is an informal label applied to a plant by humans.
Governments have formalized a definition and list to cover Noxious weeds: “A noxious weed, harmful weed or injurious weed is a weed that has been designated by an agricultural or other governing authority as a plant that is injurious to agricultural or horticultural crops, natural habitats or ecosystems, or humans or livestock”.
The difference between weeds and invasive falls into human opinion. If it threatens what we like or value, we deem it a weed. This occurs even if the plant plays a crucial role to the support of the ecoregion it is native to.
What is an aggressive plant?
A plant that spreads rapidly, or with vigor. Often difficult to contain or remove. Has the ability to outcompete plant material around it. Being aggressive is a reflection of how the plant behaves.
Examples of introduced aggressive plants are daylilies, lily of the valley, rose of sharon.
Examples of native aggressive plants are Canada anemone, Virginia creeper.
So to summarize again:
Can a native plant be invasive?
A native plant will never be invasive.
A native plant can be aggressive.
A native plant can be deemed a weed.
An invasive plant can be deemed a weed.
An introduced plant can become invasive.
And now you can tread more confidently in conversation about plants and make informed decisions when adding plants to your own garden.
