Photo: Rebecca Last
Invasive Plants on the Ottawa River
Republished with permission from Gardening at Last.
On my morning walks with Miss Mango the Magnificent, I’ve noticed an increasing number of invasive plant species along the Ottawa River. So this morning, I took along my camera to document what I saw.
Invasive Plant News from the IPBES
The big plant news this week is a new report from IPBES (Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services) quantifying the number and economic impact of invasive species globally. The news is alarming. According to the presser:
The severe global threat posed by invasive alien species is underappreciated, underestimated, and often unacknowledged. According to a major new report by the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES), more than 37,000 alien species have been introduced by many human activities to regions and biomes around the world. This conservative estimate is now rising at unprecedented rates. More than 3,500 of these are harmful invasive alien species – seriously threatening nature, nature’s contributions to people, and a good quality of life. Too often ignored until it is too late, invasive alien species pose a significant challenge to people in all regions and in every country. Approved on Saturday in Bonn, Germany, by representatives of the 143 member States of IPBES, the Assessment Report on Invasive Alien Species and their Control finds that alongside dramatic changes to biodiversity and ecosystems, the global economic cost of invasive alien species exceeded $423 billion annually in 2019, with costs having at least quadrupled every decade since 1970.
Flowering Rush (Butomus umbellatus)
This photo was taken at the storm drain outlet where Mango and I usually start our river walks. The blue bit of cloth in the water is evidence of arguably the worst invasive species – us humans. According to the Invasive Species Centre, this plant can cause several negative impacts. It displaces native vegetation and alters water quality, leading to reduced biodiversity and alterations to fish and wildlife habitat. It can impact water supply when it establishes itself in irrigation canals, reservoirs, and stormwater management ponds. Flowering rush also impacts water related recreational activities such as swimming, boating, and fishing by forming dense stands that restrict access to the water body.
Common Cocklebur (Xanthium strumarium L.)
About a meter further along the path, was this splendid specimen. Found in all provinces except Newfoundland and Labrador, the cocklebur is a big problem for soybean farmers. According to Cornell, it is an extremely competitive weed due to fast emergence and rapid growth, supported by the large seed. Populations of 1-3 plants per 10 square feet can cause soybean yield losses of 52-75% (Weaver and Lechowicz 1982). Common cocklebur emerges faster and in higher numbers (Norsworthy and Oliveira 2007c) and is more competitive (Bararpour and Oliver 1998) under tillage conditions than no-tillage conditions, so no-tillage grain production will be less favorable to this weed. Because the seedlings can emerge from deep in the soil, tine weeding and rotary hoeing have limited effectiveness.
(Shout out to my fellow Master Gardeners Caroline Koehler, Heather MacDonald, Mary Crawford and Lucie Tremblay for helping to ID this plant when I suffered a brain fart and couldn’t find it on the web.)
Lady’s Thumb (Persicaria maculosa)
Around the corner, I came across a large stand of lady’s thumb, now going into full flower. Most gardeners know this one as a weed and usually pull it before it has the chance to produce its rather pretty flower. According to OMAFRA, “Agriculture and Agri-Food Canada research has shown that lady’s thumb densities of 20,000 plants/ac can result in 13–15% yield loss in corn and soybeans.” In this location, it is easily out-competing native sedges and swamp milkweed, which grow on the floodplain here.
According to the Edible Wild Food site, the young leaves and shoot of this plant are edible. As with all wild foraged foods, be sure of plant identification, and try a small piece cautiously before tucking in for a big feed. The video at this site describes how to properly identify and use this plant.
Plantain (Plantago major)
In an open area just a few meters past that stand of lady’s thumb was another of the many plants brought to North America by Europeans. Native people call this one “white man’s footsteps”. In “Braiding Sweetgrass”, Robin Wall Kimmerer describes it as a faithful dog that follows in the footsteps of its European masters. Considered a weed in most places, I was intrigued to see its original medicinal and edible uses being honoured at the gardens of Domaine Howard in Sherbrooke, Quebec.
Invasive Bindweed and Native Hog-Peanut (Amphicarpaea bracteate)
Bindweed is a horrible problem just a few blocks upriver from where I live. In the photo above, I thought I was seeing a new kind of invasive species choking out the native sensitive fern (Onoclea sensibilis) that fills the understory of the river floodplain. To my surprise, the twining three-leaved plant is actually a native – or at least a near native. Perhaps, like the egrets I’ve been seeing along the river, climate change is enabling their move into our area.
Purple Loosestrife (Lythrum salicaria)
When you see the gorgeous purple-pink flower spikes on this stately invasive, it’s easy to understand why it was introduced as an ornamental. These days, thanks to biocontrols introduced in the early 2000s, we no longer see huge fields of purple loosestrife in what used to be wetlands. However, isolated stands still exist, like this one in the floodplain forest just a block from my home. Another surprise for me was that this plant has been moved out of the Lysimachia genus altogether. Sigh. Isn’t it hard enough to learn one Latin name?
Common (Rhamnus cathartica) and glossy buckthorn (Frangula alnus)
Among the nastiest invasives out there, common and glossy buckthorn are literal trees. Even tiny saplings are hard to pull, but it’s worth the effort as these brutes rapidly crowd out native vegetation. Less than 50 meters from where this photo was taken is a stand of the lovely native button bush (Cephalanthus occidentalis) – an unusual floodplain plant that, fortunately, is becoming more common in the horticulture trade. I’m afraid the nasty buckthorn will eventually crowd out the button bush, along with many other natives.
Buckthorn has a highly effective reproductive strategy. Those yummy-looking berries contain a laxative. Birds migrating through our area at this time of year may be tempted to sample the berries. But they contain few useful calories, and the poor birds almost immediately develop diarrhea, thus scatterng the buckthorn seeds wherever the birds relieve themselves.
Ragweed (Ambrosia spp.)
No rogue’s gallery of weeds would be complete without ragweed, the cause of many a sniffle and weepy eye – from allergies, that is! The lovely native goldenrod is often mistakenly accused because it blooms at the same time as ragweed. I was surprised to learn that ragweed is more of a near native than an invasive. In fact, there’s even an International Ragweed Society, a scientific organization that aims to promote knowledge of the weed and to control its allergenic pollen.
Canadian Coalition for Invasive Plant Regulation
You can find out more about the identification and control of invasive plants from CIPR, a new organization formed by gardeners, including several of my Master Gardener colleagues, and horticulturalists who are concerned with the spread of invasive plants.
According to CIPR, the ornamental plant trade is the largest pathway for the introduction of non-native invasive plant species in Canada. Preventing introductions and reducing the spread of these plants is the most cost-effective means to protect against their harmful impacts.
CIPR is wholly volunteer-driven. They rely on citizen scientists like us to pitch in. So if you are passionate about protecting native plant species, consider signing up to help them out.
And if you made it this far, here’s a cat picture as your reward.
About the Author – Rebecca Last
Rebecca Last has been gardening on and off since age 8 and has been a member of the Master Gardeners of Ottawa-Carleton since 2005. Her small suburban garden is certified by the Canadian Wildlife Federation as a wildlife habitat. Rebecca grows a dozen or more varieties of heritage tomatoes every year. Her garden design includes elements of permaculture, and she has been honoured to receive several awards from the Ontario horticulture community.
Republished with permission from Gardening at Last.
On my morning walks with Miss Mango the Magnificent, I’ve noticed an increasing number of invasive plant species along the Ottawa River. So this morning, I took along my camera to document what I saw.
Invasive Plant News from the IPBES
The big plant news this week is a new report from IPBES (Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services) quantifying the number and economic impact of invasive species globally. The news is alarming. According to the presser:
The severe global threat posed by invasive alien species is underappreciated, underestimated, and often unacknowledged. According to a major new report by the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES), more than 37,000 alien species have been introduced by many human activities to regions and biomes around the world. This conservative estimate is now rising at unprecedented rates. More than 3,500 of these are harmful invasive alien species – seriously threatening nature, nature’s contributions to people, and a good quality of life. Too often ignored until it is too late, invasive alien species pose a significant challenge to people in all regions and in every country. Approved on Saturday in Bonn, Germany, by representatives of the 143 member States of IPBES, the Assessment Report on Invasive Alien Species and their Control finds that alongside dramatic changes to biodiversity and ecosystems, the global economic cost of invasive alien species exceeded $423 billion annually in 2019, with costs having at least quadrupled every decade since 1970.
Flowering Rush (Butomus umbellatus)
This photo was taken at the storm drain outlet where Mango and I usually start our river walks. The blue bit of cloth in the water is evidence of arguably the worst invasive species – us humans. According to the Invasive Species Centre, this plant can cause several negative impacts. It displaces native vegetation and alters water quality, leading to reduced biodiversity and alterations to fish and wildlife habitat. It can impact water supply when it establishes itself in irrigation canals, reservoirs, and stormwater management ponds. Flowering rush also impacts water related recreational activities such as swimming, boating, and fishing by forming dense stands that restrict access to the water body.
Common Cocklebur (Xanthium strumarium L.)
About a meter further along the path, was this splendid specimen. Found in all provinces except Newfoundland and Labrador, the cocklebur is a big problem for soybean farmers. According to Cornell, it is an extremely competitive weed due to fast emergence and rapid growth, supported by the large seed. Populations of 1-3 plants per 10 square feet can cause soybean yield losses of 52-75% (Weaver and Lechowicz 1982). Common cocklebur emerges faster and in higher numbers (Norsworthy and Oliveira 2007c) and is more competitive (Bararpour and Oliver 1998) under tillage conditions than no-tillage conditions, so no-tillage grain production will be less favorable to this weed. Because the seedlings can emerge from deep in the soil, tine weeding and rotary hoeing have limited effectiveness.
(Shout out to my fellow Master Gardeners Caroline Koehler, Heather MacDonald, Mary Crawford and Lucie Tremblay for helping to ID this plant when I suffered a brain fart and couldn’t find it on the web.)
Lady’s Thumb (Persicaria maculosa)
Around the corner, I came across a large stand of lady’s thumb, now going into full flower. Most gardeners know this one as a weed and usually pull it before it has the chance to produce its rather pretty flower. According to OMAFRA, “Agriculture and Agri-Food Canada research has shown that lady’s thumb densities of 20,000 plants/ac can result in 13–15% yield loss in corn and soybeans.” In this location, it is easily out-competing native sedges and swamp milkweed, which grow on the floodplain here.
According to the Edible Wild Food site, the young leaves and shoot of this plant are edible. As with all wild foraged foods, be sure of plant identification, and try a small piece cautiously before tucking in for a big feed. The video at this site describes how to properly identify and use this plant.
Plantain (Plantago major)
In an open area just a few meters past that stand of lady’s thumb was another of the many plants brought to North America by Europeans. Native people call this one “white man’s footsteps”. In “Braiding Sweetgrass”, Robin Wall Kimmerer describes it as a faithful dog that follows in the footsteps of its European masters. Considered a weed in most places, I was intrigued to see its original medicinal and edible uses being honoured at the gardens of Domaine Howard in Sherbrooke, Quebec.
Invasive Bindweed and Native Hog-Peanut (Amphicarpaea bracteate)
Bindweed is a horrible problem just a few blocks upriver from where I live. In the photo above, I thought I was seeing a new kind of invasive species choking out the native sensitive fern (Onoclea sensibilis) that fills the understory of the river floodplain. To my surprise, the twining three-leaved plant is actually a native – or at least a near native. Perhaps, like the egrets I’ve been seeing along the river, climate change is enabling their move into our area.
Purple Loosestrife (Lythrum salicaria)
When you see the gorgeous purple-pink flower spikes on this stately invasive, it’s easy to understand why it was introduced as an ornamental. These days, thanks to biocontrols introduced in the early 2000s, we no longer see huge fields of purple loosestrife in what used to be wetlands. However, isolated stands still exist, like this one in the floodplain forest just a block from my home. Another surprise for me was that this plant has been moved out of the Lysimachia genus altogether. Sigh. Isn’t it hard enough to learn one Latin name?
Common (Rhamnus cathartica) and glossy buckthorn (Frangula alnus)
Among the nastiest invasives out there, common and glossy buckthorn are literal trees. Even tiny saplings are hard to pull, but it’s worth the effort as these brutes rapidly crowd out native vegetation. Less than 50 meters from where this photo was taken is a stand of the lovely native button bush (Cephalanthus occidentalis) – an unusual floodplain plant that, fortunately, is becoming more common in the horticulture trade. I’m afraid the nasty buckthorn will eventually crowd out the button bush, along with many other natives.
Buckthorn has a highly effective reproductive strategy. Those yummy-looking berries contain a laxative. Birds migrating through our area at this time of year may be tempted to sample the berries. But they contain few useful calories, and the poor birds almost immediately develop diarrhea, thus scatterng the buckthorn seeds wherever the birds relieve themselves.
Ragweed (Ambrosia spp.)
No rogue’s gallery of weeds would be complete without ragweed, the cause of many a sniffle and weepy eye – from allergies, that is! The lovely native goldenrod is often mistakenly accused because it blooms at the same time as ragweed. I was surprised to learn that ragweed is more of a near native than an invasive. In fact, there’s even an International Ragweed Society, a scientific organization that aims to promote knowledge of the weed and to control its allergenic pollen.
Canadian Coalition for Invasive Plant Regulation
You can find out more about the identification and control of invasive plants from CIPR, a new organization formed by gardeners, including several of my Master Gardener colleagues, and horticulturalists who are concerned with the spread of invasive plants.
According to CIPR, the ornamental plant trade is the largest pathway for the introduction of non-native invasive plant species in Canada. Preventing introductions and reducing the spread of these plants is the most cost-effective means to protect against their harmful impacts.
CIPR is wholly volunteer-driven. They rely on citizen scientists like us to pitch in. So if you are passionate about protecting native plant species, consider signing up to help them out.
And if you made it this far, here’s a cat picture as your reward.
About the Author – Rebecca Last
Rebecca Last has been gardening on and off since age 8 and has been a member of the Master Gardeners of Ottawa-Carleton since 2005. Her small suburban garden is certified by the Canadian Wildlife Federation as a wildlife habitat. Rebecca grows a dozen or more varieties of heritage tomatoes every year. Her garden design includes elements of permaculture, and she has been honoured to receive several awards from the Ontario horticulture community.
