Invasive plants: Truce or consequences?

Please check one or more of the following:

  1. ___ Do you have a yard or land near you under invasion?
  2. ___ Is it possible that you have an alien invader living in your front or backyard and you don’t know it?
  3. ___ Are you in cahoots with an invasive plant and happily providing it with a home?
  4. ___ Did you know that you could be harbouring what you thought was a friendly plant species that’s totally capable of doing a Jekyll/Hyde on you and start invading when your back is turned?

After reading this post, you may have to go back to this list and check all four.

Invasive species used ornamentally in an urban garden.

English ivy and Goutweed (both officially invasive species) used ornamentally in an urban garden, part of the Toronto Botanical Gardens tour in June, 2014.

“INVASIVE SPECIES” has become a familiar term for North Americans. Anyone close to the Great Lakes has heard of zebra mussels. If you own a boat or a lakeshore home you might be able to point one out because it’s an invasive species that’s, literally, close to home. Purple loosestrife, on the other hand, is another species generally considered evil but I wonder how many of us (gardeners or not), spying a drift of tall spiky plants with small purple flowers while taking a drive through the countryside, would know we’re looking at it and not, say, Baptisia australis or Lobelia siphilitica or Vernonia arkansana?

What if you knew for sure that you’d found a big patch of Purple Loosestrife and then discovered that there’s research suggesting it may not be as bad as we first thought? It turns out that, in fact, where an invasion of this plant has occurred, some native species may suffer but “stating that this plant has large negative impacts on wetlands is probably exaggerated.” Would you start to feel differently about Purple Loosestrife?

What if you decide to stay angry at the Purple Loosestrife and then bump into Ken Thompson, author of Where Do Camels Belong? Why Invasive Species Aren’t All Bad. He thinks battling invasive species can be a mistake. Talking to the CBC in 2014, he pointed out that nature has moved species around throughout history and that many invaders weren’t as damaging as we presumed. He also makes a case for taking into account the expense of battling the invader when we do decide to fight it. Sometimes the cure can be as harmful as the condition.

Not so sure what to think about your patch of Purple Loosestrife now? Wait! You serendipitously meet Toby Hemenway, a professor, author and permaculture advocate at a cocktail party, erm…, a volunteer tree planting project. He’s famous for declaring that the scariest invasive plant, having taken over 80 million acres in the U.S. and wiping out native habitat in the process, is called Zea mays, more commonly known as corn. “Sure, that may be true”, you argue, “but corn took over those 80 million acres thanks to us!” Well, scientists say that’s a natural process called zoochory: a plant (corn) using an animal (us) to “move their seeds around” as fellow blogger Daniel puts it in a fascinating post explaining this via beavers and water lilies on his Awkward Botany blog. Have I got your head spinning yet?

The consequences of holding a truce

Dog strangling vine growing on shrubs.

Dog Strangling vine is a Priority #1 Top Invader for the Royal Botanical Gardens where this was shot in September, 2016.

Hemenway’s viewpoint is extreme but it does illustrate that deciding what’s invasive and what’s not isn’t always straightforward and deciding what to do about some invaders isn’t getting any easier. There are the obvious bad guys–Dog Strangling Vines (Cynanchum rossicum and C. nigrum) have absolutely no redeeming qualities and no one has a problem putting them on an invasive hit list. But, as gardeners, when you look at Periwinkle, for instance (see below), or English Ivy, or Japanese Barberry, hey, why not corn and soybeans, too, then other things come into play like emotions, beliefs, politics, protecting one’s livelihood and hard practicalities. Inevitably, that’s exactly what happened when folks from conservation agencies and the horticultural industry got together during a recent event (September 8, 2016) co-hosted by the Ontario Invasive Plant Council and Landscape Ontario to discuss working together for an economically prosperous and an ecologically healthy Ontario. About halfway through the event, I had a moment. It wasn’t an Aha! moment. No, it was more like an Uh-Oh! moment and between all the botanists and conservationists, horticultural suppliers, growers, nursery owners and landscape designers in attendance, I don’t think I was the only one.

During the entire affair, which included a hike through parts of the Royal Botanical Gardens (RBG) outside Hamilton, Ontario (during which various invasive  and “potentially invasive” species were pointed out) and a tour of Connon AVK Nursery Holdings in Rockton, ON, a lot of questions were raised and no definitive answers agreed upon (not that any were expected). Everyone recognized our collective goalposts–conserving our last bits of wilderness while making our parks and gardens simultaneously pleasurable and not harmful (helpful, even) to native plants and wildlife, all while still keeping the wheels of commerce rolling. But what also became clear was that, in getting anywhere near those goalposts, we–you, me, all Canadians, all Americans, well, most everyone in the world, basically–have a hugely complex problem that involves figuring out:

  1. how to communicate to property owners, not just gardening geeks, why they should care
  2. figuring out how to communicate to property owners how they can responsibly live with invasive species
  3. how to protect native species
  4. how nursery owners can get a head’s up years in advance (since global warming is slowly turning some well behaved non-native plants into invasive ones) as to what’s going to be invasive…or whether that’s practical or even necessary.
  5. where non-native plants (aka ornamentals, aliens, cultivars) fit into this shemozzle.
Periwinkle as a ground cover in an urban garden.

Periwinkle used as a ground cover in an urban garden, part of the Toronto Botanical Gardens tour in June, 2014.

A conundrum in one plant 

On the bus ride from RBG to the Connon AVK Nurseries I met Johanna and Ted Schut, owners of Hillside Nursery in Elmwood, ON. One of their products is Periwinkle (Vinca minor). Widely considered a classic ground cover choice for ornamental gardens in North America, they’ve sold this plant for the past 25 years and, before that, Ted’s father grew and sold the plant for 27 years. Producing ornamental plants for sale is not a fast or cheap process and periwinkle is no exception. They explained to me that it takes four years to bring periwinkle stock to market during which they’ll have invested about 1750 man hours as well as paid for pots, trays, fertilizer, equipment maintenance and such.

Now Vinca minor, like several other popular ornamental plants, is featured in the Ontario’s Invading Species Awareness Program website and identified as “unwanted” in the Grow Me Instead programme. The Schuts admit that sales are half what they were in 2008 and believe part of the reason is that the plant is now considered invasive.

Periwinkle as an invasive species in the wild.

Vinca minor taking over native ground cover near Wiarton on the Bruce Peninsula, ON. Shot in May, 2014.

So what’s next? The Schuts are exploring new products for their business but, as they explained in an email to me, they’ve got a challenging balancing act “between having time and resources to diversify while [there is still a] demand for Vinca.” Additionally, the Schuts pointed out that not knowing what the Ministry of Natural Resources and Forestry will decide and when, over the past few years, has been difficult. The ministry’s Invasive Species Act 2015 comes into force next month (November, 2016).

Finding the truths in any kind of truce

The Schuts think education is important. Vinca minor, famously popular with gardeners and unpopular with conservationists, spreads vigorously by shallow rooting stems. However, if you surround this plant with a barrier so that it’s not free to spread into a nearby woods, for instance, you can effectively keep it under control. The Schuts believe the RIGHT PLANT, RIGHT PLACE philosophy applies to periwinkle. “Used the right way, it is an excellent ground cover.”

Can education be the whole answer? Ideally, being able to recognize the qualities of individual plants and where each fits into the web of life would be a game changer considering we’re technically an invasive species ourselves. But in the here and now, for those in the business of promoting plants, including non-native ornamentals, and those in the service of protecting natives, it’s not clear how many answers there really are. Or as the Schuts put it, “Did we do the right thing by planting new Vinca stock this year? Depends on who we ask.”

2 thoughts on “Invasive plants: Truce or consequences?

  1. Thanks for raising these important points about a complicated topic! Techniques for manaing “invasives” can be more toxic than finding ways to control or avoid them in the first place. I agree that getting people to understand the how/why part is very important.

    Liked by 1 person

    • I’m finding that untangling this complicated issue, if it can ever be truly straightforward, is opening up pathways to working closer with nature. That’s both challenging and exciting. But in this post-wild world, partnering with nature rather than trying to control it is really the only option.

      Liked by 1 person

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