Native alternatives to butterfly bush

Recently at the Birds & Blooms blogs, Carole Sevilla Brown wrote about the problems butterfly bush is causing in many areas of the United States. Although commonly recommended for butterfly gardeners, the most commonly available butterfly bush in the horticultural trade, Buddleja davidii, is native to east Asia and is an invasive species in many areas of the United States.

So far, Canada's cold climate has apparently prevented B. davidii from becoming naturalized here, except in parts of British Columbia (Tallent-Halsell and Watt, 2009). However, each mature butterfly bush can produce millions of seeds, and these seeds can be spread by cars and trains (Tallent-Halsell and Watt, 2009). So a butterfly bush in Toronto could contribute to the problems our neighbours to the south are facing. In addition, climate change is likely to make Ontario's climate milder and therefore put our wild spaces at greater risk from butterfly bush invasion.

Luckily, there are many alternatives for butterfly gardeners. Growing native species avoids the problems of habitat destruction caused by invasives, and can provide better attraction for butterflies by providing food for caterpillars as well as adult butterflies (Tallamy 2009).

With that in mind, here are a few flowering shrubs native to Ontario, which I found through Lady Bird Johnson Wildflower Center's Plants Database. This is a great resource for wildlife gardeners throughout the United States and Canada; you can search by state/province, habit, lifespan, light needs, moisture needs, bloom season, bloom colour, and height! Each species description at the Wildflower Center's database includes a wealth of information, including which butterflies' and moths' larvae feed on each plant, and links to their descriptions at Butterflies and Moths of North America (BAMONA).

Native Ontario shrubs to attact butterflies

• Amelanchier alnifolia (Saskatoon serviceberry): fragrant white flowers in spring. Berries are red to black in colour, attract birds, also edible for humans. Autumn foliage is yellow, orange, or red.
• Amorpha canescens (leadplant): small shrub with spikes of striking dark purple flowers in early summer; attractive silvery foliage.
• Ceanothus herbaceus (Jersey tea): umbels of white flowers in spring to early summer. Larval host for mottled duskywing (Erynnis martialis).
• Cephalanthus occidentalis (buttonbush): nifty spherical clusters of white flowers in the summer. Nutlets attract birds.
• Lindera benzoin (northern spicebush): pale yellow flowers before leaves emerge (male plants have showier flowers). Yellow autumn foliage; red berries on female plants. Larval host for spicebush swallowtail (Papilio troilus), eastern tiger swallowtail (Papilio glaucus), and promethea silkmoth (Callosamia promethea).
• Spiraea alba (white meadowsweet): spikes of white flowers in the summer, yellow autumn foliage. Larval host for spring azure (Celastrina ladon).
• Spiraea tomentosa (steeplebush): steeple-shaped clusters of pink flowers in summer. Larval host for Columbia silkmoth (Hyalophora columbia).
• Viburnum acerifolium (maple-leaf viburnum): clusters of white flowers in spring and summer followed by red to black berries which attract birds. Pinkish-purple autumn foliage! Larval host for spring azure (Celastrina ladon).

I'm so glad that Carole wrote her original post, as I didn't realize that butterfly bush was such a problem, nor did I know much about these lovely native shrubs that we can grow instead. I've got seeds for buttonbush stratifying right now, and I plan to look into some of these other shrubs as well. Please click the links for each plant to see gorgeous photos; I hope you'll be as excited about these plants as I am and try some in your garden!

Works cited

• Nita Tallent-Halsell and Michael S. Watt (2009). The Invasive Buddleja davidii. The Botanical Review, September.
• Douglas W. Tallamy (2009). Bringing nature home: How native plants sustain wildlife in our gardens (updated and expanded edition) Portland, OR: Timber Press.

Campanula rapunculoides: my new most hated plant?

I have posted before about the evils of garlic mustard (Alliaria petiolata, herbe à l'ail), which is devastating forests in the Toronto area, but in our own garden the biggest invader is Campanula rapunculoides (creeping bellflower, or as I call it, creepy bellflower, campanule fausse raiponce).

Although I knew creepy bellflower is invasive in southern Ontario, I hadn't been trying to remove it from our garden because the landlords' son is very fond of it, and it is very pretty (see photo at bottom of post). I thought I would just stop it from spreading by deadheading it. Ha.

Creepy bellflower spreads mainly by roots. It forms a thick mat of roots which make it impossible for anything else to grow. Realizing that creepy bellflower was part of the reason good plants I put in weren't making it, I decided I would try to at least thin it out.

The pile of roots above represents about an hour of hard work. Unlike garlic mustard, which pulls up quickly and easily, creepy bellflower roots break off and stay in the ground when you try to pull them up. Sites recommend digging up at least the top 15 cm of soil and removing all roots. Any bits of root remaining in the ground will regrow.

And here is the depressingly small area I removed those roots from. You can see the heart-shaped leaves of more creepy bellflower poking through the fence. I could just pull off the leaves, but that seems pretty pointless when the massive root system under and beyond the fence is inaccessible to me. I think that my landlords' son doesn't need to worry about not having his creepy bellflowers any time soon.

And here's a picture of creepy bellflower from last July. Yes, it is pretty, but it isn't prettier than the other campanulas. The USDA PLANTS Database lists three campanulas and kin native to Ontario:

• Campanula aparinoides: marsh bellflower (campanule faux-gaillet)
• Campanula rotundifolia: harebell (campanule à feuilles rondes)
• Campanulastrum americanum (formerly Campanula americana) tall bellflower (campanule d'Amérique)

Does growing invasive plants help birds?

This past week I was very excited to pick up a beautiful book, Bird by Bird Gardening by Sally Roth (Rodale, 2006), about designing gardens to attract various families of birds to the garden. And in many ways it is an excellent book, with a wealth of information about the needs of different birds in terms of food, shelter, water, etc., with lists of plants and garden plans for all sorts of lovely birds (she's an American writing for American gardeners but of course a lot of it will apply here in Canada too). It's a beautiful book, lavishly illustrated with full colour photographs, and a wealth of information.

As I read the book more closely, however, I became troubled, as she recommended plants which may be invasive in parts of the US (and Canada too, though I can't fault her for that if she wasn't intending to cover Canada in the book). For example, she suggests

• Berberis spp. (barberries, berbéris) without distinguishing between the native and invasive varieties (B. thunbergii is invasive in the northeastern US, B. vulgaris invasive in many states from coast to coast; they both are listed in the Invasive Exotic Species Ranking for Southern Ontario (PDF))
• Eucalyptus spp. (Australian natives which are invasive in California, especially, but also in the Pacific north west including part of BC)
• Euonymus alatus (winged euonymus, fusain ailé) which is invasive in the northeastern US (and southern Ontario)
• Pyrus calleryana (Callery pear, poirier de Chine) which is invasive in the eastern US

(These are just the most notorious invasives I noticed flipping through the book; I didn't do an exhaustive investigation.)

Now, there are a lot of older wildlife gardening books that recommend various invasives, especially berry plants, but I was very unhappy to see them still being recommended in such a recent book.

I was horrified when I got to a three page essay, "Invasive Implications", on pp. 74-76.

First, she implies that the term "invasive" was created by the USDA and is based on agricultural concerns, and that all non-native plants are invasive. Now, even if invasive plants were only a problem for agriculture, that is still an extremely serious problem since virtually all people in North America are completely dependent on agriculture for our food. To me that would be reason enough to avoid gardening with invasives.

Of course, in reality, there are many ecologists concerned about the impact of invasive species on ecosystems. Invasives are definitely not only a concern for farmers.

Then, she says that invasives mostly affect disturbed areas, and so are not a problem for native plants. Even if invasives only affected disturbed areas, to me that is still a problem, for they are displacing the native plants which would normally colonize disturbed areas. Invasive plants can prevent native plants from returning to disturbed areas, so this habitat is permanently rather than temporarily lost.

(And unfortunately, there are invasive species which invade undisturbed habitat; witness the heartbreaking blanket of garlic mustard (Alliaria petiolata, herbe à l'ail) carpeting the forests in High Park and around the Ontario Science Centre, for example.)

She suggests that invasives are mainly a concern in warm areas (southeast US, California, and Hawaii) or near wetlands. In reality, while invasives may be worse in those areas, that doesn't mean they aren't a serious problem here.

Then she points out that sometimes authorities use environmentally questionable practices (herbicides). There is real debate on if/when pesticides should be used to control invasives, but surely if we don't want the authorities to feel driven to use pesticides we should avoid growing plants that are invasive in the first place! She also describes an instance she witnessed of a birds' nest being destroyed when the plant they were living in was removed. Again, all the more reason to prevent these situations by not growing invasives in our gardens.

Most upsettingly, she writes that since birds use some invasives for shelter or food:

I stick up for many invasives [because] we've destroyed so much bird habitat, so many native plants, and such multitudes of insects, that I believe birds deserve some extra help.

Aargh!

The sad truth is, these invasives she's defending are a leading cause of habitat loss. In particular, the multitudes of insects she mourns depend on a multitude of native plants for food. Most herbivorous insects can only eat certain species; even a closely related non-native plant often supports many fewer insects (in both number of species and number of individuals) compared to its native counterpart. Birds can seek cover and build nests in many locations, and fruit and nectar of many plants are palatable, but without a healthy insect population most birds won't be able to get the nourishment they need.

Invasive plants don't help birds, they harm birds.

If you want to grow plants to help birds, there are many native plants (many listed in Bird by Bird Gardening, and Bringing Nature Home by Doug Tallamy) which provide shelter, berries, and the insects which are such a crucial part of many birds' diets.

For more information about the impact of native vs. non-native plants on wildlife, please read Bringing Nature Home.

Great podcasts by Doug Tallamy on gardening and wildlife

I've already mentioned Doug Tallamy's wonderful book, Bringing Nature Home (Timber Press). I just discovered these fascinating and inspiring podcasts online. Enjoy!

Part 1: the crisis faced by wildlife, making friends with insects. (8:02)

Part 2: how many native vs. non-native plants do you need, which native plants have the most benefit for wildlife. (11:11)

Part 3: how to distinguish native vs. non-native plants, how invasive plants affect the environment, using herbicides to control invasive plants, organic gardening. (9:24)

Part 4: can one garden really make a difference in helping wildlife? How to get started. (9:15)

Part 5: do lawn alternatives help wildlife, what is the most destructive landscaping practice? Current research on the impact of plants on wildlife, especially birds. Effects of native vs. invasive insects. (11:29)

Impatiens glandulifera in bloom

Warning: this is a very invasive plant in Toronto Impatiens glandulifera, known in English as "Himalayan balsam", "purple jewelweed", "policeman's helmet", "kiss-me-on-the-mountain", "ornamental jewelweed", "Washington orchid", or "Indian balsam" and in French as balsamine de l'Himalaya or impatiente de l'Himalaya, is an annual native to the Himalayas but now an invasive weed in North America, Europe, and New Zealand. The Society for Ecological Restoration ranks Himalayan balsam as a Category 1 invasive (PDF):

Aggressive invasive exotic species that can dominate a site to exclude all other species and remain dominant on the site indefinitely. These are a threat to natural areas wherever they occur because they can reproduce by means that allow them to move long distances.

So although it is very pretty, please do not plant this in your garden, and pull it up if it volunteers.

I photographed this plant in High Park.

Alliaria petiolata: seed pods

Do I really need to do yet another post about garlic mustard? Yes, because there are still zillions of garlic mustard plants invading the wild spaces of Toronto, and now they are going to seed. So if you see these plants, please remove them if at all possible! (Read Sarah Battersby's article, Top 10 Reasons to Search and Destroy: Garlic Mustard if you don't understand why this plant has to be eliminated from Toronto.)

Native, exotic, invasive: what it means and why it matters

Regular followers of this blog will have noticed that when I introduce a plant, I like to mention where it is native, and that I'm working on a list of plants that are native to Toronto.

When I first heard people talking about the importance of preserving native plants, as opposed to plants that evolved elsewhere, I didn't see why it was important. Sure, I have a sentimental attachment to our native trilliums, hepaticas, etc., and would be sad to see them go, but then I also have a sentimental attachment to a lot of the non-native weeds, like ox-eye daisy (Leucanthemum vulgare). I wondered if the concerns about the non-native plants "invading" Canada were a bit xenophobic, which seems rather hypocritical since most people criticizing invasive plants are also non-Native.

I know better now.

First, some definitions:

A native plant is one that has evolved in an area for many, many years. In practice, for North America people generally consider that the plants that were here before the Europeans came over to be native. Note that for this purpose "area" has nothing to do with political boundaries, but rather with ecoregions. Our native flora is quite similar to that of the neighbouring American states, but a plant that is native to British Columbia may not be native here. (I've seen national Canadian gardening magazines describing plants as "native" without indicating which part of Canada they're native to.)

An exotic, alien, or non-native plant is one that is not native to an area. This includes many garden plants, which have been brought over from Europe, Asia, Africa, South America, Australia, and even other areas of North America. It also includes many of our familiar wildflowers, which were brought over either deliberately or accidentally and now live without human assistance, for example Queen Anne's lace (Daucus carota, native to Europe and southwest Asia).

Why does it matter?

Why does it matter where a plant came from originally? Most of Canada's human population comes from all over the world, why shouldn't our plants reflect that? It's understandable that people would want to bring over plants from the old country. (I will admit that when I find out a plant is native to Australia, I am tempted to get it in honour of my late father, who grew up in Melbourne.)

There are two potential problems with non-native plants:

Some non-native plants have difficulty living here

A plant from a wildly different climate will have a lot of trouble coping with Canadian conditions. For example, an Australian plant would be pretty much guaranteed to die in winter. Some exotic plants require a lot of coddling to cope with our cold winters, hot summers, hail storms, snow, ice, etc. This not only means more work for the gardener, but in the case of plants that won't get through the summer without people watering them, it also means a greater drain on our natural resources. These delicate plants may also lead gardeners to use more fertlizers and pesticides than they otherwise would have done.

Some non-native plants find it too easy living here

A plant that flourishes without human attention, is "pest"-free, and tolerates a wide variety of conditions, is understandably going to appeal to a lot of gardeners. Unfortunately, these plants often don't stay in our gardens. Plants that produce tasty berries are the hardest to contain; the birds that eat the berries may poop them out kilometres away, possibly in a vulnerable ecosystem. Other plants produce seeds that travel on the wind; deadheading can prevent this, but how do you deadhead a Norway maple (Acer platanoides)?

Once these easy-going plants start growing outside of cultivation, being "pest free" gives them an unfair advantage over native plants. Most plants contain toxins in their foliage as a defence against herbivores; insects that have co-evolved with these plants have developed ways of coping with various toxins. Most herbivorous insects are specialists; these insects can only eat certain species of plants that they can detoxify. Non-native plants feed fewer or no native insects, allowing them to out-compete the native plants that our native insects eat. These species can become invasive.

An invasive plant is an exotic plant that lives in the wild without human assistance, and disrupts ecosystems. (The Society for Ecological Restoration has a useful list of invasives in southern Ontario (PDF).) Invasive plants spread prolifically, replacing native plant communities. Since most native insects can't eat these invasive plants, the population of insects declines.

So what? Even if you don't like insects (I find many of them beautiful and fascinating), insects are an important food for more "charismatic" animals. Most songbirds feed their young caterpillars; if the native plants those caterpillars eat are gone, the baby songbirds starve. The loss of native plants has repercussions throughout the foodweb. Not only the plants, but the animals who eat them, and the animals who eat those animals, and so on, go into decline as invasive plants take over.

Can we predict which exotic plants may become invasive?

Many popular garden plants, particularly food crops, are non-native. It would be nice to know which ones pose a risk to our ecosystems, so we could avoid them. Unfortunately, ecosystems are so complex and ever-changing that it's difficult to predict which plants will become invasive. Still, there are a couple of things to watch out for:

• Plants that self-sow or "naturalize readily". Yes, most of us love getting free plants, but when exotics start reproducing, will you be able to control their spread?
• Plants from a similar climate. It's no coincidence that our invasive plants come from temperate Eurasia. Here they can find the climate they're adapted to, without the insects and diseases that kept their populations in check back home.

When I first learned about the dangers of invasive plants, I assumed that "heirloom" varieties would be safe. Surely if people have been growing a plant in Toronto for a century without a problem, it's not going to invade now, I thought. Unfortunately, I was wrong. In Bringing Nature Home (Portland, OR: Timber Press, 2007), Douglas W. Tallamy documents many seriously invasive plants which were well-behaved garden plants for decades before becoming a problem.

You would think that an exotic plant that is very similar to a native plant could fit into our ecosystems without causing problems, but we can't assume that either. Tallamy reports that even closely related plants support far fewer insects than their native counterparts. Here in Ontario, European frogbit (Hydrocharis morsus-ranae is one of the most serious invasive plants according to the Canadian Wildlife Service. It forms dense mats on the waters surface which prevent native plants from growing underneath. Yet European frogbit looks virtually the same as the native American frogbit (Limnobium spongia); the only visible difference is that the native frogbit has a grooved stem.

Implications for our gardens

Although most of us will continue to grow some non-natives, especially foods and herbs, it's clearly better for the environment to

• choose natives rather than non-natives whenever possible (see the Ontario section of the North American Native Plant Society Sources List)
• don't buy plants known to be invasive (check the list! (PDF))
• prevent non-natives in the garden from spreading elsewhere if possible (deadhead, plant in containers rather than directly in the ground, etc.)
• remove invasive plants from the garden, especially those whose spread is difficult to control (if it's a tree, check out Toronto's Private Tree By-law before proceeding—you may need a permit)

Increasing our use of native plants can let us enjoy beautiful gardens while preserving the beauty of our wilderness.

Convolvulus arvensis

Warning: this plant is moderately invasive in Toronto.

Convolvulus arvensis, known in English as "field bindweed" and in French as liseron des champs, is a perennial native to Eurasia which is now found throughout most of North America. The flowers are white, turning pink with age, and show a clear resemblance to their cousins the morning glories (e.g. Ipomoea purpurea, Ipomoea tricolor).

According to Invasive Exotic Species Ranking for Southern Ontario, field bindweed is moderately invasive here. A native which looks similar, only with larger, showier flowers, is hedge false bindweed (Calystegia sepium).

I photographed this plant in Almonte, Ontario.

Hesperis matronalis

Warning: this is a very invasive plant in southern Ontario Hesperis matronalis, known in English as "dame's rocket", "damask violet", "dame’s violet", "dames-wort", "dame’s gillyflower", "night-scented gillyflower", "queen’s gillyflower", "rogue’s gillyflower", "summer lilac", "sweet rocket", "mother-of-the-evening" or "winter gillyflower", and in French as julienne des dames is a biennial or short-lived perennial native to Eurasia. It can be distinguished from similar-looking phloxes by the four petals (phlox has 5 petals).

This is a very pretty flower, and it is easy to see why some gardeners allow it or even encourage it in their gardens. Unfortunately, here in southern Ontario dame's rocket is seriously invasive. According to Invasive Exotic Species Ranking for Southern Ontario, dames rocket is a Category 1 invasive (the worst category, like the dreaded garlic mustard). They describe Category 1 species as follows:

Aggressive invasive exotic species that can dominate a site to exclude all other species and remain dominant on the site indefinitely. These are a threat to natural areas wherever they occur because they can reproduce by means that allow them to move long distances. Many of these are dispersed by birds, wind, water, or vegetative reproduction.

These are the top priority for control, but control may be difficult. Eradication may be the only option for long-term success.

Similar-looking alternatives for Toronto gardeners include Phlox pilosa (native) or Phlox paniculata (not native, but not invasive and widely available).

Convallaria majalis: flowers

Warning: this plant is invasive in Toronto. Convallaria majalis, known in English as "lily-of-the-valley" and in French as muguet de mai is a perennial native to Eurasia. Its attractive scented white flowers which are easy to grow in somewhat difficult conditions, for example as a ground cover in shady locations, have made it a popular garden plant. Unfortunately, in Toronto it is an invasive species; SER Ontario ranks it as Category 3: "moderately invasive but can become locally dominant when the proper conditions exist" in their Invasive Exotic Species Ranking for Southern Ontario.

Here is a large colony (about 2-3 metres across) of Convallaria growing in the middle of the forest at High Park. I don't know if this colony got its start by an uninformed human deliberately planting it here, or if it was introduced by nonhuman means such as birds. Once the first plant grows, it spreads by rhizomes to form large colonies.

Polygonum cuspidatum: foliage

Warning: this is an invasive plant in Toronto. Polygonum cuspidatum, known in English as "Japanese knotweed", "fleeceflower", "Himalayan fleece vine", "monkeyweed", "Hancock's curse", "elephant ears", "pea shooters", "donkey rhubarb", "Japanese bamboo", "American bamboo", and "Mexican bamboo", and in French as renouée du Japon or renouée du Siebold is a herbaceous perennial native to east Asia which is invasive in North America and Europe. SER Ontario ranks it as Category 2: "Exotic species that are highly invasive but tend to only dominate certain niches or do not spread rapidly from major concentrations." in their Invasive Exotic Species Ranking for Southern Ontario (PDF).

I photographed this plant at High Park.

Alliaria petiolata: flowers and seed pods

Warning: this is an extremely invasive plant in Toronto.

Yes, I know, this is my third post about garlic mustard in May, but this is the first time I've shown the fully opened flowers and nefarious seed pods of this plant. Here you can see how garlic mustard practically forms a monoculture. (Photo taken in High Park, south of the Black Oak Café).

Here's a close-up of the flowers and seed pods. If you missed it, or if you aren't convinced that this plant should be uprooted on sight (at least in North America), reread my post about why garlic mustard is horrible. Then read Sarah's article, Top 10 Reasons to Search and Destroy Garlic Mustard. Then if you still aren't convinced, google it and see why experts agree this plant does not belong here in North America.

Acer negundo seedling

Warning: this is an invasive species in southern Ontario.

Acer negundo, known in English as "Manitoba maple", "box elder", "boxelder maple", or "maple ash", and in French as érable du Manitoba or érable negundo, is a deciduous tree native to eastern and central United states and southern Alberta, Saskatchewan and Manitoba.

I like finding volunteer tree seedlings in the yard and was disappointed to find out that this was Manitoba maple, which the Invasive Exotic Species Ranking for Southern Ontario (PDF) ranks as a category 1 invasive, "Aggressive invasive exotic species that can dominate a site to exclude all other species and remain dominant on the site indefinitely." At least this one is small enough to be removed fairly easily (I'm assuming).

Alliara petiolata: flower buds

This is an extremely invasive species in Toronto. Although I just posted a whole long thing about why garlic mustard is evil, I haven't posted a picture of the flower buds. I was disheartened to see it's that time of year again already. Photo taken at Wilket Creek Park.

Alliaria petiolata: foliage

This is an extremely invasive species in Toronto. Alliaria petiolata, known in English as "garlic mustard" and in French as alliaire officinale ou herbe à ail is a biennial native to Eurasia and northern Africa. It is one of the worst invasive plants in Toronto.

Garlic mustard was originally brought to Canada from Europe as a food plant. Unfortunately, it has flourished too well. Garlic mustard is not edible to Canadian wildlife, it emerges early in the spring before many native plants, it produces large numbers of seeds, and it harms mycorrhizal fungi that native plants need to grow properly. These factors give it an advantage over native plants, with the result that it can invade forests and outcompete them. There are areas of the forest in High Park that are completely overrun with garlic mustard, at the expense of native plants. Garlic mustard is invading the forest around the Ontario Science Centre as well, endangering their beautiful white trilliums. Because Canadian wildlife won't eat garlic mustard, replacing native plants with garlic mustard means less food for wild animals and therefore a loss of animal as well as plant biodiversity.

For these and other reasons it is important for Toronto gardeners to be able to recognize garlic mustard and remove it. In the first year, garlic mustard forms a low rosette of heart- or kidney-shaped leaves with a jagged edge. The leaves have a distinctive garlicky smell when crushed. In the second year, the plant produces a stem 30-60 cm tall with clusters of small, white, four-petalled flowers. The flowers are followed by skinny upright seed pods, but please don't let it get to that stage if you can help it. After setting seed, the plant dies, which is good news. (There are some good photos of garlic mustard leaves, flowers, and seed pods on this page by the Plant Conservation Alliance Alien Plant Working Group.)

To control garlic mustard, remove the entire plant in the first year, or remove at the very least the flowers in the second year (in erosion-prone sites you may want to leave the roots of second year plants in place, but cut the plants off close to the ground, otherwise more flowers can form in the leaf axils). Don't leave the flowers or unripe seedpods lying around as even if cut off from the root they can still ripen and produce viable seed. You can eat the plants if you like; here's a recipe for garlic mustard pesto (I haven't tried it myself yet).

Garlic mustard seed in the soil remains viable for years, so eradicating it is a long-term project. So let's make it a May tradition to enjoy a walk outside eradicating garlic mustard!

Tussilago farfara: flowers

Caution: invasive Tussilago farafara, known in English as "coltsfoot" and in French as pas d'âne, is a perennial native to Eurasia. I had never seen it before and was intrigued by its apparent absence of leaves; apparently a rosette of broad leaves will emerge later on; their shape reminded whoever thought of the common names of a colt's foot or donkey's foot.

The Invasive Exotic Species Ranking for Southern Ontario rates coltsfoot as Category 4 ("Exotic species that do not pose a serious threat to natural areas unless they are competing directly with more desirable vegetation.")

Coltsfoot has traditionally been used medicinally, but is toxic in large doses. Also, European Journal of Pediatrics reported a case of an infant who developed hepatic veno-occlusive disease after regular consumption of what his parents thought was coltsfoot, but was actually Adenostyles alliariae, which shows the importance of being cautious about gathering and self-treating with wild plants.

I photographed these plants at the University of Toronto downtown campus on St. George north of College.

Vinca minor: flowers

Warning: this is an invasive species in Toronto.

Here's what Vinca minor looks like in bloom. Very pretty. Too bad it's invasive. The City of Toronto advises residents to not plant Vinca minor.

Verbascum thapsus: leaves

Don't plant this—it's invasive!

Verbascum thapsus, known in English as great mullein or common mullein, and in French as molène thapsus, molène Bouillon-blanc, Bouillon-blanc or Bouillon jaune is a biennial native to Eurasia and north Africa. In Canada it is generally considered a weed, and a number of sources call it invasive.

Here you can see some of the old foliage from last year, and a rosette of new leaves opening in the middle. The soft velvety leaves are rather nice, but do we really need more of this plant spreading itself around and invading wild spaces, where it displaces native plants?

Vinca minor: foliage

Please don't plant this; it's invasive!

Vinca minor, known in English as "common periwinkle" or "lesser periwinkle" and in French as petite pervenche, is an evergreen trailing subshrub native to Eurasia with pretty blue flowers. Unfortunately, like English ivy, periwinkle is an invasive species here in Toronto. The Invasive Exotic Species Ranking for Southern Ontario puts it in Category 2: "Exotic species that are highly invasive but tend to only dominate certain niches or do not spread rapidly from major concentrations." Toronto's Urban Forestry Service recommends not planting periwinkle if you live in Toronto.

So yes, it's a very pretty plant, but it really is hard to justify growing it in our part of the world, especially when there are a zillion plants native to Toronto you could grow instead.

Hedera helix

Please don't plant this; it's invasive!

Hedera helix, known in English as "English ivy" or "common ivy" and in French as lierre grimpante, is an evergreen climbing perennial native to Europe. Unfortunately, in Toronto it is invasive. Invasive Exotic Species Ranking for Southern Ontario says it is a Category 3 Invasive: "Exotic species that are moderately invasive but can become locally dominant when the proper conditions exist." The City of Toronto's Urban Forestry Service recommends not planting it.

This photo of English ivy completely covering a front yard in Toronto shows why this is a popular plant (how many ways are there to have a green "lawn" all year around in Toronto) but also why it is a problem. Native plants are going to have a hard time pushing up through this; the ivy also has an edge because it is evergreen, unlike most native plants around here. According to the Plant Conservation Alliance (US), when English ivy climbs trees it can actually kill them.

English ivy produces berries; birds eat the berries and spread its seeds. So this is not an easy plant to contain.

I can certainly understand the temptation to grow English ivy; it is pretty, and I almost bought some myself last year before I learned about it. Now I think it's just not worth the risk, especially when there are many many species native to Toronto you could grow instead.