Building and maintaining gardens is similar in many ways to other constructive hobbies and art forms. Take the base materials, use specialized tools to manipulate and position them in relation to one another in a way that creates an aesthetic appeal that is more than the sum of their individual parts. There is a major difference between gardening and something like sculpting or painting*, though: the “base materials” of gardens (plants) are living, self-reproducing organisms. Paint and marble will not grow and take over an art gallery or escape from an outdoor exhibit to proliferate in the surrounding grounds.

The word “invasive” is out and about in the world now (a reproducing meme in and of itself) but in case you haven’t heard it, I’ll give you my definition: a characteristic of an introduced species (plant, insect, fungus, microbe, bird, reptile or otherwise) to escape containment and proliferate outside^. Invasive species are a big deal, they cost billions of dollars to governments around the world (mostly by out-competing crops, blocking water ways and by being expensive to remove). We all know the stories of how Australia has been plagued by wave after wave of ill-conceived introductions of Rabbits, Cain Toads and Dingoes etc. etc. In Canada, millions of dollars are spent just at the boarder to stop invasive plants (and crops pathogens, among other things) from coming across in cargo. Recently, Ontario passed the Invasive Species Act which acknowledges the problem and provide an “official” source of information, though it doesn’t enforce any of its recommendations.

When I am choosing plants for a garden, I feel the weight of my decisions and it drives me to research the species, their origin and potential invasiveness before I buy them. Just quickly googling the scientific name of the plant followed by “invasive” usually does the trick. Within 10 minutes or so of research I can answer the following questions and make a decision:

1. Is this plant native to the area where I am going to plant it? I feel that a 100 km radius is a fair range and I give a lot of leniency here especially to the south (+). If Yes, we’re probably good; if No, continue to question 2.

2. Can the plant survive in that area without my help? The vast majority of crops can not: I was barely able to keep my tomatoes alive last year despite quite a lot of effort. I grew a Passion Flower vine outside once that basically melted on the first day of sub-zero temperature. If No, we’re probably good; If Yes, continue to question 3.

3. Can the plant reproduce in that area? In the absence of strong evidence to the contrary, any fruit/seed set should be considered viable. Also, don’t forget about asexual reproduction by budding (some cacti have become invasive by this mechanism) and root propagation (mint spread this way even if the seeds are not viable). Some tough invasive plants can even reproduce from small fragments of stem or root (Phragmites and Japanese Knotweed, for example, spread mainly in this way). If Yes then I would not plant that species outside (and even if you do, or if you choose to grow it indoors please do everything you can to contain it including pinching off flowers and burning all parts of the plant when you’re done with it). If No then it will probably be OK to plant it outside.

All of that can be boiled down into one question that I ask myself every time I put a plant in the ground: What would happen if this thing escaped? For native plants the answer is: AMAZING! that actually what I am trying to accomplish. For most crops the answer is: it will probably die immediately or at most persist for a generation or two before fading out (%). For the vast majority of “conventional garden” plants you can buy at a nursery or garden center the answer is: I’m not sure, but maybe something really really bad. That’s why I stick to native plants and crops almost exclusively.

Personally, I just couldn’t imagine bearing the weight of having been the source for a new population of an invasive plant. (Yes, I have seen this happen: Periwinkle flowing down from a garden into the adjacent forest; aquarium plants covering the surface of a rural wetland; eurasian honeysuckle permeating throughout a certain botanical garden’s natural areas). If I caused something like that, I would feel like I had personally released a plague into the world. That alone is reason enough for me to steer clear of the “conventional garden” plants. I understand that other people will have a different perspective on this, and that the powers of tradition and fashion combined are very strong influences. Whatever your perspective, your aesthetic, your favorite plant species, if you are reading these words, hear them ringing in your head the next time you buy a plant for your garden: “Am I Being A Responsible Gardener?”

*I think music is somewhere in-between on this scale: ever hummed a melody that was stuck in your head only to pass the “earworm” on to someone else?

^My biological perspective urges me to see this in a different way: in the Anthropocene era, humans have reconnected the continents into Pangaea (virtually, thorough land and sea travel) and those species that are able to take advantage of these new bridges, arrive in a new niche, outcompete the current residents and proliferate…. from their perspective it’s a huge success (as a white human, I’m part such a colonial wave). In biology terms, the only things that matter are: Arrive, Survive, Thrive, Reproduce, Disperse, Arrive, Survive, Thrive, Reproduce, Disperse…and on and on forever. Of course, the biological perspective isn’t the only thing that matters.

(+). Because I feel these species are going to migrate north due to climate change anyway and/or were already on their way back after being pushed out by the glaciers 10 000 years ago

(%) In biology nerd speak, this is called a “waif” species