The most hated plant in North America

Today is a very special blog post, brought to you by one of my very best(est) friends, Tanya! Everyone say Hi to Tanya! (Hi Tanya!) Tanya gets to work outside all day every day (OK, not all day every day, but she gets to be outside A LOT with her job), and has some really awesome pictures of really unusual plants in North America. This one certainly isn't uncommon, but that doesn't make it any less special! This blog is her first (of hopefully many!) guest post for my blog, and she's writing about a plant most of us absolutely hate. And if you don't know if you hate it...do you get a runny nose and red, itchy eyes in the fall? Yes? Then you hate this plant. Trust me :)

Without further ramblings by yours truly, take it away Tanya!

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Species name: Ambrosia artemisiifolia

Common name: common ragweed, annual ragweed

Location: top image from our guest contributor; images 2, 3, and 5 from melody at Dave's Garden (available HERE); image 4 from htop at Dave's Garden (available HERE)

There may be another plant that a greater number of people despise (dandelions, maybe?), but for sheer intensity of feeling, I would argue that the most hated plant around must be Common Ragweed (Ambrosia artemisiifolia).  Every year in mid-August, many of us get that old, familiar itchy-eyes and runny-nose feeling that sends us running for filtered, air-conditioned air and antihistamines, and Common Ragweed is most likely the culprit.   

As Jen mentions in THIS POST, many people blame their fall allergies on showy flowering plants like the innocent goldenrods.  But, in order to cause your allergic reaction, you must breathe in the pollen grains, which means that the plant you’re allergic to is wind-pollinated: the plant produces lots and lots of pollen light enough to be blown around in the wind, and it’s betting that some of it will land on the female parts of another plant of the same species.  Plants that use this strategy have small, inconspicuous flowers because they don’t need to expend energy to attract pollinators like bees and butterflies to carry the pollen around for them.  Common Ragweed falls into this category: its pollen can be carried by the wind for hundreds of kilometers.  It’s hard to get away from this stuff.

Common Ragweed is native to North America (Jen says: I put "non-native" for the species status so that I could have a diagram with the "Invasive" box highlighted!) but has become an invasive species in Europe and Japan.  It is a “supertramp” species (yes, that’s a legitimate ecological term), which means that it produces lots of seed, disperses widely, and does really well in disturbed habitats. When you start looking for Common Ragweed, you’ll most likely find it in highly disturbed areas, like beside roads and in agricultural fields rather than stable forested areas, so really, it’s all our fault there’s so much of this stuff around: we’ve created lots of habitat for it!  There’s probably much more Common Ragweed around now than there was when Europeans arrived in North America.  You can burn it, pull it, mow it, or kill it with chemicals, but it will most likely come back in full force the very next year.  A good argument for increasing the amount of healthy forest and grassland habitats where Common Ragweed can’t compete, I say.

Ragweed leaves are compound and finely divided, and look a little like Wild Carrot (Daucus carota, which you can read all about in THIS POST) or Yarrow (Achillea millefolium, which you can read all about in THIS POST).  The flowers and seeds are produced in a tall spike called a raceme, and the plant grows to be about one meter in height.  This means that, in many areas, it isn’t completely covered by snow throughout the winter, and any of the seeds remaining on the plant remain accessible to animals like birds and small mammals.  The seeds have a very high oil content too, which makes them even more valuable to wildlife.  When Common Ragweed is causing you or your loved ones autumn misery, think about the mice and voles that will be depending on their stored ragweed seeds to survive until spring... and in the process, spreading them all over the place so there will be lots more for next year!

The North American planetree

Species name: Platanus x acerifolia

Common name: London planetree

Location: Western University campus

As promised, this blog is about our version ("our" referring to the North American meaning of the term) of the planetree. Ironically enough, it's called the London planetree not after London, Ontario, but after London, England. A half-British, half-American name for a European species. Just when you thought common names couldn't get any more perplexing... :)

The planetree is a hybrid, which makes its native range essentially a moot point. But for the purpose of a species status diagram, it's a non-native species since the hybrid is rumoured to have been first discovered in Spain in the 1700s, but was first officially described by a Scot in 1789 as a variety of the Oriental sycamore, or Platanus orientalis. It was elevated to the status of species in 1805 by Willdenow (Platanus acerifolia), but it is now widely believed to be a hybrid of the American sycamore and the Oriental sycamore (sometimes called the Chinese sycamore or even the Oriental plane). It looks like an exact intermediary of the two species: has leaves with lobes not nearly as shallow as the American sycamore but more shallow than the Chinese sycamore, fruits in pairs instead of singly like the American sycamore (the Chinese sycamore usually has 3-6 fruits in a group), and light green inner bark unlike the white bark of the American sycamore and the much darker green bark of the Chinese sycamore. I love it when hybrids are a 50/50 blend of the parent species! It makes life so easy.

So why would you want to plant a hybrid species, when the American sycamore is a native species and looks pretty darn similar? Well, for one, the planetree is much more tolerant of urban conditions like pollution and root compaction, as well as being much more drought-tolerant and so doesn't require the riparian habitat that the American sycamore does. It also doesn't get nearly as large, which is often beneficial in cities (you don't exactly want a 5 meter in circumference tree growing between a sidewalk and a road). It is also much, much less susceptible to a fungal disease called anthracnose, which is quite common in American sycamores. So far it sounds like a pretty good compromise! Unfortunately, all good things must come to an end. The planetree actually has a really nasty side to it in the spring: it is highly allergenic. The new growth of the tree produces tiny hairs on the surface of the leaves, the leaf buds, the branches, and the fruits. As the tree sheds these hairs while it matures, they blow off in the air and (usually) end up up your nose. Here, they attach to just about anything they can get ahold of, and trigger a severe immune response (this isn't just your typical pollen-allergy runny nose). Some people have even reported a skin response that looks like a second-degree burn as a result of coming into contact with many of these hairs (say, for example, grabbing onto a young branch in the spring) and the resulting rash is a hyper-immune response. This effect tends to decrease as the tree ages, but if you plant a young tree, be warned. Now that I know this, you won't catch me coming anywhere near one of these trees in the spring. I have really sensitive skin, and with my luck I'd be the one that ends up with giant pustules all over my hands and arms! The leaves are also difficult to deal with in urban settings as the leaves produced on mature branches are very thick and leathery. If left to rest where they fall, they can take years to start to decompose (unlike a few months like most leaves, which is why they make great compost starters and mulch). This means they are problematic to deal with in the fall clean-up to prepare streets for winter.

Planetrees are sometimes planted for lumber and logging purposes because of the very attractive wood (it's a light yellow wood with red flecks). In the lumber industry it's often referred to as Lacewood, and is used in wood trim or decorative panels in fine furniture.

The tree of anything-but-heaven

Species name: Ailanthus altissima

Common name: Tree of Heaven

Location: Ontario

Unfortunately, there are a couple pretty impressive specimens of the Tree of Heaven on campus, and this is only going to lead to disaster in a few years. The Tree of Heaven is a highly invasive species in North America, spreading underground via rhizomes and producing suckers that grow quite vigorously and grow in girth very quickly. This can not only be a menace to lawnmowers if this plant is in a decorative location, but they harbour a nasty secret underground. The Tree of Heaven produces some of the most toxic natural herbicides known, which successfully kill off any vegetation growing near them. While they don't seem to produce these chemicals in great numbers directly around their root system (other plants that aren't grasses can live happily in their shade if they are shade tolerant), they are produced in large amounts from the rhizomes to protect the developing suckers. This double-whammy of colonization and making the soil toxic to other organisms allows for their success at complete dominance over an ecosystem. They also thrive in disturbed areas where other species are slow to establish, also contributing to their success as an invasive species.

If you needed another reason not to plant this tree, it reeks. And I mean it smells TERRIBLE. The Chinese (the tree is native to China) even have their own traditional name for the tree: chouchun. Roughly translated, this means "malodorous tree." Other English names for this tree is the ghetto palm (not entirely sure how it got this name, but I kind of like it...) and the stinking tree. The odor probably has to do with the allelopathic compounds produced from the rhizomes; the suckers are especially disgusting after being "decapitated" with a lawnmower. It's almost enough to make you not want to go outside for fear of being drowned in their stench. On the bright side, this tree rarely lives past 50 years, so if you've got one in your yard you might want to remove it before it falls on your house.

Despite the incredibly foul smell produced from these trees, they are incredibly important in Traditional Chinese Medicine, where almost the entire plant is used for various purposes. A word of warning; this plant is toxic to humans as well as all other animal life so extreme caution should be exerted should you decide to go the TCM route. The bark is made into an astringent to treat a wide variety of diseases and disorders, from intestinal hemorrhaging to dysentery. There is also a significant amount of chemicals that are similar to quinones in the bark, and quinone is the most important antimalarial drug in the world. The drug-resistant malaria (or multi-drug resistant malaria) seems to still show strong effects of susceptibility to the ailanthone in the bark of the Tree of Heaven, and so is now a recognized antimalarial drug. The fruit of the tree when made into a tincture that effectively treats a vaginal infection called trichomoniasis, an infection caused by a protozoan that can be very difficult to treat. It is now the leading treatment for the infection by both doctors practicing Traditional Chinese Medicine and by doctors practicing Western medicine. It has also been suggested that this same medication will also have some effect on cancerous cells, but this has never been substantiated with clinical evidence. Extracts from the tree also have very potent anti-inflammatory effects, and have been shown to be incredibly effective at resolving severe allergic reactions (known as anaphylaxis).

Lovely Lavender

Species name: Lavandula angustifolia (formerly L. occidentalis)

Common name: English Lavender

Location: Ontario

You might think this plant is native to England or the surrounding area, but you would of course be incorrect (don't you love it when that happens?!). This plant is actually native to the western Mediterranean near the Pyrenees mountains in Spain. It is an incredibly popular ornamental, medicinal and culinary plant which first gained popularity amongst the British, hence the common name. In fact, the British are the biggest users of lavender products in the world.

This species of plant is considered to be evergreen in most areas of the world, meaning that it doesn't lose its leaves during the winter. It is cold-tolerant and drought-tolerant, but quite sensitive to continuously wet soils. If you wanted to plant this in your garden, it would do best in high-lying areas to ensure well-draining soil. Due to the incredibly aromatic leaves and flowers, the plants suffer from very little herbivory, and the essential oil is so potent that it prevents most types of microbial growth on the plant. The chances of it being eliminated from a garden (or agricultural plantation) due to disease is quite slim. The flowers contain a large amount of nectar for their size and are great attractants of pollinators. In fact, the lavender essential oil remains intact after nectar processing by bees to make honey, so lavender honey is one of the few honeys that naturally have a flowery taste. There are a few other "specialty" honeys for sale out there, but many of them are artificially spiked with flavouring during the processing (by humans) from honeycomb to jar.

Aside from ornamental use, lavender flowers have been used in culinary applications for many centuries. The French use it in a special herb blend called "Herbes de Provence" which was made popular in the 1970s in North America. The British also use lavender flowers in tea and in making pastries and creams.

Medicinally, lavender oil is often mixed with some other sort of carrier oil (it is very difficult to obtain large amounts of lavender essential oil and it also has a very potent smell, so it must be diluted) and used in aromatherapy. During World War I, lavender oil was a popular anti-infection oil used to treat open wounds. It does have quite powerful antimicrobial properties, and is still sometimes used for that purpose today (in "herbal medicine").

A word of caution: lavender oil is a VERY powerful allergen. Some people are allergic to it in concentrations as little as 0.25%, and most people will show some sort of reaction at as little as 1% solution. For this reason, it is strongly suggested from all medical professionals that you refrain from using lavender oil in any form on children under the age of 2. The type of reaction it causes is photosensitivity, and applying it on sensitive skin can cause reactions as severe as second degree burns which can leave permanent scarring. ALWAYS read the label before you purchase lavender oil, and make sure that the concentration of oil is less than 1%. If you can't tell, don't buy it or don't use it on your skin. The leaves and flowers of lavender when used in traditional amounts in cooking are never enough to produce 0.25% of essential oil so not to worry if you enjoy using them in cooking (or eating lavender honey or lavender jelly). Just don't make a meal out of lavender leaves!

As another word of caution, there was evidence in 2007 that stated lavender oil (as well as tea tree oil) can cause gynaecomastia, or breast development in young boys, due to its estrogenic activity. This was refuted in 2008, but be cautious. Just yet another reason to avoid using lavender oil as any form of medical treatment on young children!

It's a creeper! It's a crawler! It's English Ivy!

Species name: Hedera helix

Common name: Common ivy, English ivy

Location: Ontario

As you can probably guess from the common name of this plant, its origins are in Europe (and also Asia). It's a somewhat unusual plant in that it is an evergreen species, which contributes to its invasive properties in that it can photosynthesize in the winter. This plant produces structures called rootlets along the stem, which help anchor the vine to any surface that's suitable. When there isn't a suitable surface, they act as regular roots by anchoring the plant into the ground and absorbing water and some nutrients. If you're really observant, you'll notice in the top two pics that English ivy and Madagascar periwinkle (that you can read all about in a previous blog post HERE) seem to be able to live together quite nicely, completely covering the ground with their vines (and that's a relatively high traffic area, too). Both plants must be flooding-tolerant, since that location in the back yard can get incredibly soggy during the spring melt and during the summer's intense rains. The ability of this plant to out-compete other plants is so impressive that English ivy often creates "ivy deserts" where it has strangled out all other plants and is all that exists on a landscape. This can be contrasted with the plant kudzu, which is an invasive vine in the United States that has choked out ground cover, shrubs and trees in Florida and Georgia (and is moving its way north).

John Gerard plays an important role in the historical uses of this plant, like Solomon's seal. He once advocated that soaking leaves in warm water would create a tonic that could be used to help eye soreness and dryness. I would absolutely not recommend this as a modern treatment for dry eyes (aside from the fact that you should never, EVER mess with "home treatments" when it comes to your sight) since English ivy can produce an intense allergic reaction upon contact with a chemical contained in the leaves called falcarinol. On the skin it produces contact dermatitis (a rash-like reaction), but in contact with the eyes it can induce blindness if you're sensitive to the chemical. Interestingly enough, most people with this sensitivity usually greatly dislike carrots since they also contain the same chemical and can produce an "itchy mouth" (I'm sure there's got to be a technical term for that...). Historically, the berries of this plant have also been used to treat bronchitis.

To love and to cherish

Species name: Lamprocapnos spectabilis

Common name: Bleeding hearts

Location: Ontario

Bleeding hearts are some of my favourite flowers because they’re a great example of flower shape variation in the plant kingdom. I took this picture in my back yard, where they were growing along a steep slope that most rainwater entering the back yard runs down. They can tolerate soil that’s occasionally very wet as long as the soil drains well. Like all really odd-looking, showy plants in Southern Canada, bleeding hearts are native to Asia and were brought over to North America to be used as ornamental plants. While their flowers are extremely convoluted and most insects find it difficult to reach the nectaries of the flowers, these plants are remarkably successful at reproducing. This implies that they have found at least one insect partner that helps them cross-pollinate. Growing this plant where you are likely to come into contact with it is not recommended if you have sensitive skin; it contains a chemical that can cause rash, itchiness and general discomfort. This plant also has a white variety, but it's significantly less spectacular when flowering than the pink version.