Are All Unwanted Species Actually Invasive?

Are All Unwanted Species Actually Invasive?
Are All Unwanted Species Actually Invasive?

The term ‘invasive’ gets thrown around a lot when it comes to talking about plants that are aggressive growers, or that aren’t native to a particular region. It’s understandable when many of those plants are unwanted in our gardens! But are all of these plants invasive in the Sea to Sky? What exactly does it mean for a species to be invasive?

The term ‘invasive’ actually has a very specific definition. An invasive species is not native to a specific area and causes either ecological or economic harm. By ‘not native’, we mean that it could have been found in a particular region before human intervention caused it to spread. Many of the invasive species in the Sea to Sky region are native to Europe or Asia.

Ecological or economic harm could mean many things.

Scotch Broom infestation

Ecological harm could mean:

  • Outcompeting native species
  • Being toxic to humans and wildlife
  • Altering water flow
  • Increasing wildfire risk, etc

Some examples of how invasives can cause economic harm are:

  • Reducing crop yields
  • Damaging infrastructure, and
  • Decreasing property values.

Not invasive everywhere

Different regions have different lists of invasive species, depending on their native species populations and the surrounding environment. At SSISC, we have our own list of species we consider to be invasive in the Sea to Sky region, as do most other regions. There’s also a BC-wide list, and a Canada-wide list!

Invasive species are also controlled differently in each region and at each site, depending on a number of factors, including:

  • Priority level
  • Extent of the infestation
  • Site characteristics
  • Considerations of the land holder/manager
  • Available budget
  • Species’ characteristics (plant biology)
  • etc.

Horsetail, Stinging Nettle, and Devil’s Club

Are all non-native species invasive?

Not all species that are non-native are invasive. Some introduced (exotic) species are harmless to the rest of the ecosystem or don’t escape the gardens where they are planted. While many invasive species are voracious spreaders and growers, introduced species are non-native, but not ecologically or economically harmful.

So what about all of those species that are native to an area, but are unwanted in our gardens? Horsetail, for example, is a prolific spreader. However, since it’s native to the Sea to Sky region, it is not considered invasive.

Stinging Nettle is another great example of a native species that you definitely don’t want growing in your garden. While it is great for foraging and its medicinal qualities, its sting may not make it worth growing at home. Despite its painful properties, this species is not invasive as it plays an important role in our ecosystem.

Yet another example of a native species that can cause harm is Devil’s Club. The latin name for this species is Oplopanax horridus – quite a fitting name, if you’ve ever had the pleasure of being stung! But, again, this species is not considered invasive because it’s native to the Sea to Sky.

Many people use the term ‘invasive’ to describe plants with prolific growth habits. If you’re a gardener, you probably know that mint should be planted in a pot, not directly in the soil, unless you want an entire garden full of it. Despite its ability to spread quickly and the fact that it’s not native to our area, mint is not considered invasive. While it may tend to take over flower beds and garden plots, it doesn’t cause harm to the environment, the economy or human health like Yellow Lamium, Purple Deadnettle and Purple Loosestrife, which are mint’s invasive cousins.

Lemon balm and oregano are other examples of commonly-planted herbs that are exotic (non-native), but not invasive. Like mint, they are prolific spreaders that should be contained to pots. While they can also be pesky to get rid of once established, they won’t wreak havoc on our native ecosystems or cause economic harm.

Unwanted but not invasive

Many plant species in our area may not be welcome in our gardens, but that doesn’t necessarily make them invasive. Invasive species are only the species that are both non-native to a particular region, and ecologically or economically harmful. Check out our Invasive Species Profile Pages to learn more about which species are invasive in the Sea to Sky region, and what you can do about them!

Horsetail Photo credit: gwhetham, iNaturalist

Stinging Nettle Photo credit: johndreynolds, iNaturalist

Devil’s Club Photo credit: aerisc, iNaturalist

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