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Learning about Colonization in a Backyard Garden

Gardening seems to consist of pulling out one kind of plant and replacing it with a plant of another kind. Makes me wonder how natural modern backyards are and how kind to the environment, especially native plants. How do decorative plants, flowers, shrubs, and trees, fit in the native/invasive/cultivated plant story1?

It makes me think of the settling of North America by Europeans. Let me explain by looking at my garden.

If I don’t interfere with plant life in by urban yard, it will fill with invasive species from other ecosystems rather than plants that are native to my area. This is because we humans have been spying new and interesting looking plants for centuries, digging them up on one continent and planting them on another. And selectively breeding either native plants or the ones we’ve imported from elsewhere to have more exotic colours, flowers or fruits.

Sometimes, this results in barely viable plants, other times it leads to a wild orgy of colonization, overwhelming the local ecosystem by aggressive, greedy species that won’t settle for a bit of land to raise a small community of its kind, intermingling politely with the established species. No, the invasive species has to find a spot, leave some seeds, see another spot that looks nice, leave some more seeds, see a spot where other plants are growing but know its seeds will do better in the area…and on it goes until entire tracts of land are filled with one type of plant and the rest die out due to lack of nutrients. 

Native plants are susceptible to being overtaken by foreign species because they live in a balance with all the other native species. Each has its time, spot in the soil/sun/season. It’s not in their DNA to dominate, or colonize.

Let me look at the microcosm of my garden to think about current the plant population. 

Plants I spend time pulling up = weeds:

  • dandelions
  • clover
  • broad-leaved plantain
  • goldenrod

Ontario has a list of weeds that even includes the smokeable stuff2, although the term is subjective. One person’s weed is another’s bedding plant. Add in the concept of wildflowers3 and a movement to more natural habitats means plants on the weed list can be purchased from fancy garden centres. I love phlox, and let this plant spread all over my flower beds. Some might point to roadside ditches full of phlox as evidence they’re weeds. The same might be said for day lilies. My neighbour grows goldenrod in the front yard, liking their late summer colour. Dandelions are edible, providing value to some, although they were brought to North America by European settlers and have many traits of invasive species. My functional definition of a weed is an unvalued plant that is determined to grow and needs to be removed to conserve nutrients for preferred plants. 

Plants I spend time pulling up = invasive species:

  • Manitoba maple trees (native to the Prairies, invasive in Ontario because they choke out other plant life in the forest)4
  • dogstrangling vines (from Europe 120 years ago)5
  • Virginia creeper (considered a weed in Ontario but is acting like an invasive species in my backyard – all over everything, especially choking cedar and lilac borders)
  • violets (sweet violet is on the list of potentially invasive plants in Ontario)6
  • Japanese knotweed (brought from Asia for desirable landscaping properties) 7

An invasive species is one that will grow quickly and occupy large sections of land, sucking up so much water and other nutrients that any other species cannot live. Often the impact goes beyond plants, to specific insects that would have flourished on the native plants, and the critters that would have thrived because of the insects. (This includes either eating the insects or secondary effects, such as crops for human consumption from plants pollinated by bees.) Some invasive species cause specific damage – for example, dog-strangling vine decoys monarch butterfly into laying eggs but doesn’t support the larva, making them into effective butterfly-baby killers. Other damage is more general, like Japanese knotweed that sucks and mines the life out of everywhere it lives, making it impossible for other plants to survive.

Native plants I try to encourage:

  • columbines
  • ostrich ferns
  • red maple trees8

Non-native plants that need lots of nurturing and encouragement, which I do because they are beautiful and not invasive:

  • roses: the history of roses is very complex and involves much back and forth, selective breeding and grafting between plants from Europe, China and North America9 – there are native species in Canada, wth smaller, less showy flowers, 
  • peonies: have a somewhat similar origin story to roses, originating in China and Europe but broadly disseminated10
  • annuals like snap dragons (native in North America but not necessarily southern Ontario11), nasturtiums (native to South and central America12) and morning glories (native to central America/Mexico)13

I see a metaphor in gardening for European colonization of Canada and a way of understanding what is beneficial to our environment and what is excessive and overbearing.

The extremes are simple to understand:

When only the original inhabitants were in Canada, there was harmony and sharing. Everyone had enough, and no one took an excess at someone else’s stake. 

With colonizers that take a greedy share, wanting more and more, there is damage and destruction of established inhabitants. Harmony and balance is lost.

This is the history, of colonization by both newcomer people and plants, but in the present day we are trying to find a better approach. Original inhabitants and more recent settlers are both here, trying to co-exist after much trauma to the original inhabitants. Realizing there is beauty, bounty and benefit in all, the way forward is to carefully find new balance, respecting the needs of all, but never satisfying one groups needs by making the other’s secondary. 

In the garden, I encourage the native plants, nuture the cultivated and imported plants, keep the invasive species under control, and find beauty in all. 

In pots, imported morning glories and nasturiums. In the background, native ostrich ferns and imported dappled willow. Trees include the invasive Manitoba maple, imported black walnut and native larch and cedar.

1 Planting to grow food, as opposed to eating what grows, is an added complexity in this story, which I will leave to another post. 

2 Here a long list of weeds from Ontario’s Ministry of Agriculture …

3 As a child, I understood wildflowers as those found in uncultivated areas – roadsides, field and forests. They weren’t as showy or displayable as cultured flowers. They are mostly native species. Fortunately, over the decades since I was a child, these species have become recognized as valuable for their beauty and resilience.





8 Oops. I have confused the trees I think are the good ones (they look nice and grow politely in my yard) with an actually invasive species. Red maples are native to Ontario, but Norway maples are non-Native (guess where they came from, based on the name) and while they look like red maples they are invasive in the forest setting because they choke out the growth on the forest floor.






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