Acting locally: How native plants can help you confront invasive species
Invasive plants can seem harmless. Heck, they can even you look beautiful! But left unmanaged, invasive trees, vines and reeds can wreak havoc on the local ecosystems they invade.
On the eastern edges toronto, Friends of the Red Watershed (FRW) has been dealing with invasions for decades. The community organization works to protect, restore and rejuvenate Forests, streams, wetlands and meadows Environments In and around Rouge National Urban Park, including nature-based approaches to reducing and mitigating invasive plants. The best part? FRW does this by planting and stewarding native plants – which also store carbon, provide habitat for at-risk species, and help protect against floods.
What can you learn from doing FRW to keep unwanted plants away? And what can you do to manage invasive species in your backyard? We dig into it with Jim Robbwhich has been working to protect and restore the Rouge Valley for nearly 40 years He has been General Manager of FRW since 1997.
Many people might be surprised to learn that invasive species are a problem in and around cities – especially ones as large as Toronto. Can you explain why invaders love urban environments?
If you are in a huge natural area, where there are mainly native species, Mother Nature can handle most disturbed sites – and she can do it better than us. But in the city it is different. Here in Toronto, we have invasive plants introduced — sometimes accidentally, sometimes by European colonizers — like Norway maples, Siberian elms, Russian olives, European buckthorn, and plants like dog strangler vine, garlic mustard, and bergamot. (Also known as common reed). We also have a lot of non-native birds, like European starlings and English sparrows, that eat these non-native seeds and spread them in their droppings.
Invaders thrive in damaged or disturbed areas, and many of them are found in and near cities. Invasive species haven’t co-evolved with the creatures and insects that live here, so they’re kind of free. Because they have less competition, they go crazy.
Why do these plants pose such a threat?
They tend to grow vigorously and outcompete native species. Take garlic mustard, for example. They release chemicals that are harmful to things like trillium, trout lily, and other plants that grow under local maple forests. It is difficult to manage. Something like the dog strangle vine will grow very aggressively around native trees and plants, literally choking their growth.
Then there is Pragmat. It grows tall, and is actually a very beautiful herb – it turns golden brown over the winter and has a kind of beautiful fox tail on top. But they are replacing our native grasses, which are home to red-winged blackbirds, muskrats, beavers, and all manner of waterfowl. Phragmites are salt-tolerant, so they can outcompete native plants along road ditches where there is a lot of salt. Also, fleas send out roots several meters long every year, and wherever they touch the ground, they can start a new colony. If the excavator is working and digs the ground somewhere that has sphagnum roots, and the piece of root gets stuck in the frame of the excavator, and then moves somewhere else, that little piece of root can take root and establish a colony. Thirty-five years ago, I only knew of one location where phragmites were found (in our area). Now there are probably 50,000 sites. Therefore, phragmites have become a big problem.
If left alone, these invasive plants will spread and take over. What works to stop them?
Chemicals like glyphosate certainly kill these species, but the environmental and health risks are too great. We (at FRW) don’t use any chemicals, and we hope anyone would if they did very Sparingly.
Removing invasive plants can also work, but it requires a lot of time, resources, and dedication. To get rid of garlic mustard, you must continue to uproot it for three consecutive years, and hikers need to stay on trails in natural areas so as not to introduce its seeds into other areas with their shoes.
To be honest, we don’t spend a huge amount of time removing infestations. Of course, if we see an invasive growth on a site we’re working on, we’ll uproot it or cut it back, depending on the plant. But in the long term, we believe the best strategy for fighting invasive species is by introducing more native species and expanding natural areas.
why is that?
Invasive species thrive and spread in areas where small patches of natural habitat are broken up into frequently disturbed areas, such as roads, railway lines, waterways, urban areas and agricultural fields.
When you expand a natural area by planting a lot of native species, you increase the amount of native seeds compared to invasive seeds, so it becomes a possibility. You are more likely to obtain native seed land somewhere and colonize it. When you have larger landscapes, there are fewer outer edges that non-native species can invade, and more core areas where native species can dominate.
Can you give an example of how this approach worked for you?
We carefully choose to include native plant and tree species that are best at competing with the invasive species we want to eliminate.
We have successfully gotten rid of phragmites by planting some fast-growing native white pines. Phragmites require sun, so once the trees grow tall enough, Phragmites become shaded and stop growing.
This seems to require a lot of patience. How do you know it works?
We have been doing this work for over 36 years. At the sites we have restored, native species are making a significant comeback, and invasions are reducing as the sites mature and natural processes are restored. So, I’m very optimistic that if we can continue to defragment the landscape and create larger, more interconnected landscapes, invasions will become more manageable.
How can people follow this approach at home?
You can make a difference in your backyard, or even your apartment balcony, by planting native plants, flowers, shrubs and trees.
The really encouraging thing is that so many people have now set up local plant nurseries – and they are growing not only for people working in environmental protection and restoration, like us, but also for home and property owners. The local plants they offer are amazing. There are lots of beautiful wildflowers available and most of them are perennials that live for many years. Something like a dense, glowing star, you can plant it in many sunny spots in the city. Or swamp milkweed, which will grow in non-swampland, supporting monarch butterflies and bumblebees.
What advice do you have for people looking to get started?
You can research plants native to your area and start gradually. It can be as simple as removing a non-native plant and replacing it with a native plant.
There are so many native species to choose from, and they are so beautiful. Most are perennials, so they come back every year, and the initial cost is about the same as non-native species, such as pansies. Even if you want to keep some of your favorite non-native species, that’s fine, but if you add more native species, you’ll be in a better position to attract native butterflies and birds, and keep out invasive species.
You’ll get more biodiversity, and you’ll get more beauty!
FRW is one of six organizations currently supported by WWF Canada’s Nature and Climate Grant Program, offered in partnership with Aviva Canada.