INVASIVE, exotic and alien are terms used to describe plants that are not normally growing in a particular ecosystem at a given point in history.
The debate over native versus exotic species continues to rage on with the purists on one side claiming only native plants are good for our environment. On the other side, the skeptics and some scientists who are not so sure that exotic species are damaging the environment, perhaps exotic plants are simply practising accelerated evolution with help from man.
I recently read a book review on patternliteracy. com by Toby Hemenway who has been an adjunct professor at Portland State University, scholar-in-residence at Pacific University, and is currently a field director at the Permaculture Research Institute USA. In Hemenway's review of David Theodoropoulos's book Invasion Biology: Critique of a Pseudoscience, Hemenway says, "Lately, I've noticed some thinning of the ranks of the natives-only army, and the debate has grown much more nuanced and sophisticated.
Many people still cling to the simplistic battle cry of "natives good, exotics bad" that was once almost the only view to be heard - or to get funding. But the murmurs of a few questioning voices have now grown to a full-scale argument, with a growing body of data on the 'don't blame exotics' side." Hemenway goes on to say the debate now "ranges beyond an examination of invasive-plant science (more properly, the lack it) and also explores the psychological, political, and cultural reasons behind our eagerness to hate certain species."
What is a native plant and what is not? Few scientists have dared to delve into the realm of culture and politics that so deeply pervades the war on exotic plants to provide a clear definition that would answer such a question. Depending on when you lived on Earth, various plants have been native or exotic to various regions of the world. There were once coniferous forests in the tundra. Does that make coniferous trees exotic to the tundra now?
The battle cry of the city dweller "Kill all exotic species!" rings a little hollow and pious in light of the real environmental problems that all of us are inflicting on the planet everyday. You want to save the world, try recycling. You want to save tropical forests, try buying coffee that is fair trade certified. You want healthy food choices that do not poison the world's farmland with pesticides, try buying organic.
But I digress. I have growing in my backyard a large Manitoba maple (Acer negundo) that spans much of my yard. She's a big, old, beautiful tree that harbours life in many forms. Birds especially
like this tree as a roost and a place to find food in the thick layer of moss that covers the branches.
Manitoba maple is native to central and parts of eastern North America. According to the exotics movement my tree is an alien species that should be eradicated. Am I exaggerating?
Perhaps, but not much.
Let's take a plant we all know such as the tasty Himalayan blackberry (proper scientific name is Rubus armeniacus) that grows wild everywhere. This invasive plant is an exotic species that feeds birds, bears and other animals not to mention people during late summer. Its benefit to native animals is unofficially known though not yet scientifically proven.
Are we going to kill all the blackberries in the province just because it's exotic? Not likely, probably not affordable or even possible at this point in time.
Let's be realistic.
Spending time and money controlling every exotic plant is wasteful and frankly useless because it's too late in many cases because we already let the genie out of the bottle and maybe there are benefits that we are overlooking. And I love the taste of Himalayan blackberries.
If you have exotic plants growing in your garden and you want to get rid of them there's only one way to do it. Use an excavator and dig out root and stem. If you cannot get a machine in, then dig by hand. You can also plant coniferous trees like fir, cedar and hemlock that will eventually shade and crowd out the exotic plants.
Personally, I am against lasagna mulching (layers of cardboard and newspaper applied as suffocation mulch) as a control measure because it occupies valuable garden space for too long, making the location unusable.
As for chemical control methods, listen to the purists and they will tell you they are winning the war on Japanese knotweed by injecting the stems with pesticide, in locations that are usually located along streams and rivers, right where we legislatively prohibit and do not want pesticides used.
Anyone besides me see a problem there?
So who's winning the war; exotic plants, native plants, purists, skeptics or co-evolution?