Green tea: won't cause you to lose weight or prevent cancer, but tastes good!

Species name: Camelia sinensis

Common name: tea plant, tea tree (see below for why you should never call this plant a tea tree), tea shrub

Location: teaching lab at Western

For the last "Plants as a Human Resource plant profile," I figured I would do one of my favourite plants in the world, and one that I exploit multiple times per day: the tea plant. The tea plant (often referred to by it's Latin genus, "Camelia") is native to China, as are all plants with the species epithet "sinensis" (it means "from China"). There are two major varieties of tea plants: one that was domesticated in India and the Middle East called Assam tea (C. sinensis var. assammica), and the other that was domesticated in China and known as Chinese tea (C. sinensis var. sinensis). There are two other recognized varieties but these are only used locally for tea, not shipped to international markets. If the tea you buy is just referred to as "tea," you can be almost guaranteed that it refers to Chinese tea, as Assam tea is almost always specified on the label. It does have a slightly different taste, and when the leaves are cured it brings out the difference in flavour. It would be appropriate to note here why I say above that the term "tea tree" should probably not be used to refer to this plant, despite the fact that it can reach "tree height." When you call something a tea tree, most people think of an essential oil that is referred to as tea tree oil, used in cosmetics and in fragrances (sometimes now used medicinally in herbal medicine, too). This is NOT the same species, and this extract is from the leaves of the tea tree plant, or Melaleuca alternifolia. Please don't drink tea tree oil...your digestive system will hate you for it.

One thing that catches many people off-guard is that ALL types of tea (black, white, green, yellow, oolong, and pu'erh) come from this plant. The way that the leaves are treated after picking is what determines what type of tea the leaves will become. There are also differences in when the leaves are picked, and how many are used in the making of different types of tea.

Black tea: leaves are picked and then allowed to fully oxidize. The leaves are fully oxidized when they turn black and start to roll inwards. The leaves may then be dried and packaged (being cut before or after drying, or left whole), or they may be flavoured before drying. Earl Grey tea has bergamot flavouring added before drying (bergamot oil is extracted from the skin of the bergamot orange), English breakfast tea is made up of plain black tea leaves, Irish breakfast is a blend of Chinese and Assam tea leaves, and Masala chai is a blend of black tea leaves and other spices (and often sugar).

Green tea: the newest leaves are picked, rolled, and immediately dried with minimal oxidization. This allows for a much milder taste, and a taste that blends well with other flavours for tea blends (like dried fruit pieces or other mild flavourings like flower petals). The quality of the leaves, the amount of time they are given to develop on the plant, and the environmental conditions the plant was subjected to during growth all play major roles in the flavour of the tea. Lower-quality teas have a much more bitter after-taste to them than higher-quality teas, and if you compare a good quality green tea to a poorer quality green tea in a taste test you'll be able to tell the difference right away. Because of the lack of oxidization of the leaves, this leaves all of the chemicals intact that many claim have health effects (more on that later).

Matcha tea: this is just a specific cultivar of tea plant where the leaves are dried without oxidization and then ground into a powder. This powder is whisked into warm water until a frothy-like consistency is reached, and then consumed. Many proponents of green tea having positive health effects say that matcha has a much larger effect on health because the leaves themselves are also consumed (unlike drinking traditional green tea).

White tea: this is a special type of green tea, where the leaves are allowed to wither on the plant before they are picked and dried. This prevents the oxidization process, but the leaves are "bleached" on the plant so they are nearly white in colour. This is emphasized by the fact that the leaves are very young and still have a dense covering of white hairs, which make the leaves look even lighter in colour. The term "white tea" does not refer to the colour of the beverage, just like "green tea" doesn't refer to a beverage that is green. If you get a cup of white tea that looks like water...you've just been served water. If you get a cup of green tea that is green (and it's not matcha, which is bright green in colour), you've been served a cup of bad quality green tea and green food colouring.

Yellow tea: this is a relatively uncommon type of tea, where the leaves are allowed essentially to rot slightly while being dried very slowly. This gives the leaves a yellow-ish appearance, and gives a very different flavour to the tea. I have yet to try yellow tea (or see it for sale in many places) myself. Sometimes the term "yellow tea" is used to refer to tea that is either green tea or white tea that is served in the Imperial court (just to make things more complicated).

Oolong tea: this type of tea is almost an intermediate between white tea and black tea. The leaves on the tea plant are allowed to wither during extreme sun exposure during the hottest months of the year, then picked and fermented (not fully fermented like black tea, but fermented enough to give a smoky and full-bodied flavour). The amount of fermentation depends on the quality of the leaves picked, and in some areas in China only one specific cultivar is used to make oolong teas. The withering of the leaves causes them to curl and twist, so watching oolong absorb water during steeping is often a sight to be seen. What looks like tiny little fragments of tea leaves actually unfurl into complete leaves. It's like magic!

Pu'erh tea: this is a type of tea produced exclusively in Yunnan Province in China, and it is made by fermenting and oxidizing the leaves of the tea plant after drying. This gives the leaves a very unique flavour which is difficult to describe, but also allows for customized fermentation and oxidation prior to shipping. The leaves are, more often than not, packaged in "cakes" to be sold and wrapped in decorative foil. This actually allows for the continuous oxidation and fermentation of the leaves during shipping and storage, which is referred to as "aging" the tea. Sometimes tea cakes are shipped immediately and may be aged by the purchaser or used right away (the flavour, and colour of the steeped tea, differs drastically depending on amount of time left to age). Other times tea cakes are allowed to age at the factory, then shipped. These are usually consumed immediately, and are very expensive to buy. The cakes are packaged with "tickets," that are always stamped with a four-digit number. The first two of these numbers represent the year in which the recipe for that specific type of pu'erh cake was developed, the third number refers to the grade of the leaves used (the smaller the better), and the last digit refers to the specific factory in which it was made. To use the leaves, they are often just chipped off the cake until the desired amount is separated, but sometimes the entire cake may be steamed to loosen all of the leaves (and then they would be stored in an airtight container after re-drying). Often a pu'erh knife is used to loosen shavings of leaves from the outer surface; you never take a "slice" of a pu'erh cake because the amount of fermentation and oxidation from the outside to the inside of the cake differs drastically. Sometimes pu'erh tea can taste "fishy" if it is fermented or oxidized too quickly, which is often a sign of poor quality. Choose your pu'erh wisely!

Onto the health effects of tea. For the most part, black tea might be a tasty beverage but it is almost entirely lacking in the polyphenols that tea is known for. If you want to drink tea to be healthy, put the Earl Grey and English breakfast back on the shelf and find yourself a good-quality green tea. There are four diseases or disorders that tea has been shown to have proven positive effects, as demonstrated in large-scale clinical trials. The first is in calming the symptoms of asthma. When green tea is consumed on a regular basis it can act as a bronchodilator, which would increase the air flow to the lungs. This does NOT mean that if you're having an asthma attack you crack out the green tea and make yourself a cup. "Green tea therapy" for asthma is used in conjunction with emergency inhalers and also the everyday inhalers; the idea is that asthma attacks will occur less often, be less severe, and everyday inhalers could be at lower doses and be used less frequently. The next three diseases all have to do with dilating the vascular system; regular consumption of green tea has been shown to help decrease the severity of angina, peripheral vascular disease, and coronary heart disease by increasing the diameter of the blood vessels, allowing for better blood circulation. This definitely won't cure any of the above diseases or prevent you from getting them, but if you are at high risk of developing any of them then it may help prolong the onset (or decrease the severity of the symptoms). That being said, the number one and number two risk factors for all three of those disease are no longer related to inheritance from your parents; they're now obesity and smoking. So do yourself a favour and quit smoking and get out and exercise!

There are a lot of other claims out there about the health benefits of drinking green tea, but so far none of them, I'll repeat that in big letters, NONE OF THEM, have been demonstrated to be true in large-scale clinical trials. People will tell you drinking green tea regularly will decrease your cholesterol and prevent the onset of cancer, neither of which have been demonstrated. Extracts from the tea leaves from the plant (the key here is from FRESH leaves. Are these chemicals still there in quantities that are useful to the body after drying and then steeping in boiling water? Unlikely) have been shown to have anti-cancer properties and the ability to reduce cholesterol but these effects have never been demonstrated in humans. There's also the strong suggestion that drinking green tea will contribute to weight loss, which I find incredibly hard to believe. Any kind of caffeine intake will "contribute" to weight loss if you don't take in more calories than you burn, because caffeine is a stimulant. Will drinking green tea specifically cause you to lose weight? No. Exercise and burning more calories than you consume causes you to lose weight. If you want to lose it, you need to put in the effort. Don't fool yourself into thinking you can drink some tea or take a pill made of green tea extracts and the pounds will melt off.

So are there any benefits to drinking green tea, other than the four mentioned above? Well, the jury's still out. There's evidence that the consumption of green tea SHOULD be beneficial, but nothing has been proven yet. That being said, there's absolutely no evidence that green tea is harmful to you, and if you're concerned about pesticide use there are now an over abundance of companies that produce organic green tea. Just don't go overboard; remember that tea does contain caffeine (although much less than coffee), and if you're drinking it to be healthy you can't be adding milk (or worse, cream!) or sugar. Learn to love the purity of the leaves :)

Will this plant really repel mosquitos?

Species name: Cymbopogon citratus

Common name: lemon grass

Location: teaching lab at Western

Lemon grass (or lemongrass. Same thing) is native to southeast Asia, which should be intuitive for those that cook international cuisine (or local cuisine, I guess, if you're in Thailand or the Philippines!) since it is heavily used in Thai and Filipino dishes. If you've never seen the full plant before (as opposed to just the bulbous bottom of the stalk in the grocery store like in the third photo), you'll notice it looks a whole lot like ornamental grasses you might grow in your garden if you live in temperate North America, like zebra grass (which you can read all about HERE). This species of plant, while not in the same genus as zebra grass, is a close relative and in the grass family.

Like ginger (profiled a few days ago in a blog entry that you can read HERE), lemon grass has a ligule that is useful in identification of the species. It is a very unusual ligule in that there are long hair-like appendages that protrude out of the base of the blade of each leaf, and the papery part of the ligule is short and has nearly a straight edge (which is unusual for a ligule; usually they're longer in the middle than they are on either side and somewhat semi-circular shaped). It's a pretty characteristic ligule, and I'm ashamed to say I didn't get a great picture of it when I had the chance. I'll have to go track down this plant in the greenhouse and make sure I get a good picture of it! Like other grass plants, but unlike ginger, lemon grass has very non-descript flowers that are pollinated by the wind (and that is actually a photo of the flowers in the fourth photograph). This is a characteristic of nearly all species in the grass family, where the amount of resources necessary to allocate to a "pretty" flower used to attract insects or small animals (like hummingbirds or even mice) is far more than it is just to give way to the wind and rely on having your pollen blown from plant to plant. This is partly attributed to the habitat in which most grasses live; wind is abundant in prairie habitats and cheap to use. If you rely on living pollinators to cross-pollinate your flowers, you may run the risk one day of having pollen ready before there are pollinators around to transport it for you. Grasses have evolved "simplified" flowers to eliminate this risk and maximize the potential for pollination. Smart grasses!

As well as the great citrusy flavour lemon grass imparts on food and beverages, lemon grass has been used in folk medicine around the world for centuries. In Brazil it is believed to by an anxiolytic and hypnotic plant, but anyone who has ever had Thai food or lemon grass tea could probably speak to the lack of both of these effects, even when the plant is consumed in large quantities or consumed in a more concentrated form like chewing the stem. In fact, no scientific studies have ever substantiated this claim. Lab studies, however, have shown that this plant has the potential to show some medicinal value. It does show cytoprotective and antioxidant properties, suggesting that this may somehow one day play a role in cancer prevention (no known method of exploiting antioxidants to either prevent aging or prevent the development of age-related cancers currently exists, no matter what anyone tells you). One of the chemicals in the extracted essential oils of lemon grass has been suggested to play a role as an antihypertensive, and in lab studies the pure form, called citronellol, has been shown to lower blood pressure in mice and rats so there is definitely the potential to use this chemical as a potential blood pressure herbal medicine. There have been very few reports of this plant being toxic to any kind of domestic animal (human or non-human pets), so you don't have to worry much if you grow your own lemon grass. Cats anyway will stay away from it because it smells like citrus; unless you've got an atypical cat, cats hate any kind of citrus. Lemon grass oil has been reported to cause mild skin rashes in people with sensitive skin, so if you have extremely sensitive skin be careful handling the fresh-cut plant.

Sometimes extracts from this plant are referred to by the commercial name "citronella," which many of you will recognize as an insect repellant. So does it work? In my experience, no. There is no amount of citronella that you can burn or put on your skin that will truly deter the bugs you are determined to deter: mosquitos (and sometimes deer flies and horse flies). You can never truly "deter" a mosquito. They are out for blood (literally), and "smell" you via the carbon dioxide in concentrated forms that you exhale (which you can't prevent yourself from doing) and by the chemicals you exude in your sweat. Deet is the only chemical that can truly make you "invisible" to mosquitos by camouflaging your scent and throwing off the mosquito's radar. Deet does wear off incredibly quickly, so if you're in an area with a high density of mosquitos you can essentially be guaranteed to be bitten anyway (especially if it's hot and you're sweating, effectively both increasing your hormonal signal to the mosquitos and washing off the deet at the same time). Some people are naturally more alluring to mosquitos because they give off more of the mosquito signal chemical, and so they require more deet more often (I am, unfortunately, one of those people...). By rubbing citronella all over yourself, you're just making yourself smell more like lemons than you are like a human. This can work for about 30 seconds to deter mosquitos, but it is not going to work in the long term. Sorry for ruining your day if you use citronella oil as a bug repellant and have been wondering why you still get bit all this time :)

Does this mean citronella NEVER works against deterring bugs? No, it doesn't mean that. Remember that essential oils produced by plants are secondary compounds usually used in plant defence? Well, it smells like lemons for a reason. Citronella IS actually an effective insect repellant; clinical studies have shown that it is nearly 100% effective in deterring fruit flies from a specific area where it is applied, and it doesn't have to be applied in large quantities. It also does a pretty effective job of deterring stable flies, which bite not only humans but also horses and cows if they get a chance (and these bites are incredibly painful, bloody, and result in enormous welts on the skin). Citronella oil definitely does have a good use in insect deterrence, just don't expect it to do anything for mosquitos!

Three geraniums for your Sunday

Going along with the theme of "plants on display in the lab room of a course I TA," I have a series of three different, yet closely related, plants for this blog. The first one is a plant I've blogged about before, and the next two are unique (and I didn't even know they existed until I started with this course; now I'm trying to track them down to plant them in my garden somewhere!). The first image shows all of them together so you can get a bit of perspective about size difference and how they differ from each other on a "big picture" scale, then I'll profile each one of them separately.

This image gives away a bit of the surprise (hindsight: take the cardboard cheats out of the way before photographing next time!), but the major difference between these three species of geranium is how they smell. The one in the middle is the "ordinary" geranium, and the pots on each side are geraniums that each have unique smells that I force the students to identify (I'm awesome like that; I make my students use their senses in labs...I even make them taste plants! Don't worry, I ask about allergies at the very beginning so I don't kill anyone by accident). So let's get smelling!

Species name: Pelargonium x hortorum

Common name: common geranium

Location: teaching lab at Western

This first plant is probably the most easily identified species of any kind of geranium because they're so gosh darn common! Especially in North America, it seems like everyone, everywhere has planted at least one geranium plant in their garden in the spring (some climates in North America in the southern United States would provide ideal growth conditions to allow for the growth of geraniums all year; they are perennial plants in ideal conditions). The colour of flowers can differ drastically, as can the shape and general morphology of the leaves of the plant. The common geranium is native to southern Africa, where it is actually now nearly threatened in the wild because of habitat loss and the increasing frequency of severe drought. I have blogged about this plant twice before in two different forms; you can read all about the two cultivars HERE and HERE.

The easiest way to identify a "regular" geranium is by looking at the leaves (very fleshy and almost furry on both sides) and the flowers (the characteristic five petals with the stigma in the middle that's star-shaped; you might need to click on the image of the flower to make it larger to see it). Since other species of geraniums are less likely to flower both in general and in captivity (putting other species of geraniums in pots makes them significantly less likely to flower, but they do also have different flowering times so they might not have been "in season" at the time I took these photos), we'll concentrate on the leaves as methods of distinguishing these species.

Species name: Pelargonium crispum

Common name: lemon scented geranium

Location: teaching lab at Western

You can see right away that this species is quite different from the previous, "common" geranium in two ways. The first one is the way that the plant grows. Instead of it being a low, bushy plant, it instead grows thick, woody stems and the leaves are concentrated at the top of these stems. This is partly attributed to the general differences in growth habit of these species, but also a difference in breeding; the common geranium has been selectively bred over centuries to maintain a "low and bushy" growth form because it is more pleasing to gardeners. If you let the plant grow long enough indoors (or live in a climate where this species survives year-round), you'll notice it start to get taller and more wiry as it ages. Pruning can prevent this by keeping the plant short, but since the flowers only emerge from the top of the plant pruning is generally discouraged. It's much easier to just rip it out and replant it if you want to keep it short, or just learn to love a straggly geranium bush.

This species is also native to southern Africa, but is much more common in the wild because of its natural defence mechanism: the scented leaves. The plant hasn't just developed this ability to please humans; it has actually evolved as a way of deterring herbivores from eating the plant. The regular hairs on geranium leaves are called trichomes. The lemon scented geranium also has these trichomes on the leaves, but they also have specialized trichomes called glandular trichomes. These have a swelling at the tip of the hair that contains a tiny droplet of oil. When we separate the bulge from the rest of the hair we get this over-powering smell of lemon (the scent is very similar to Lemon Pledge, if you've ever used that for dusting then you'll recognize the smell immediately), but to a herbivore this means "STAY AWAY!" If a herbivore is silly enough to consume the leaf anyway, then they will in all likelihood be killed (if small) or learn to never do that ever again (if they're larger). The oil droplets contain potent chemicals that are toxic in large quantities; humans would have to ingest an entire plant in order to feel any ill effects so you don't have to worry about any accidental poisonings if you happen to own this plant (there is no reported toxic effects on cats and dogs, but you might want to play it safe and keep them away from it anyway). You will want to be careful, however, with this plant around very young children as the oil in the droplets can be very irritating to sensitive skin (and babies and young children generally have the most sensitive skin, especially on their hands, arms and face). As an aside (a relevant one): I have chewed on one of these leaves just to "try it out," and let me tell you. Not a pleasant experience. It doesn't taste AT ALL like it smells. Word to the wise.

The overall leaf shape of this species is also very different than a common geranium. The leaves are much more lobed than the common geranium, and there is a notch (or a "crisp," where the Latin name of this species comes from) at the end of every leaf vein. They are still fleshy like the common geranium, but another difference between them is that this leaf is much longer than it is wide, where the common geranium has almost a round leaf and at times even wider than it is long in some cultivars.

Species name: Pelargonium grassularioides

Common name: coconut scented geranium

Location: teaching lab at Western

The last plant we have as an example of the diversity of growth form in geranium plants is the coconut scented geranium. This species, also native to southern Africa, is much more common in the wild than the previous two, but not much is actually known about its current state of population abundance and successful reproduction. As it does share a native range with the previous two species, it can be assumed that this species would also be threatened by habitat loss but it can also tolerate much more harsh conditions than the previous two species; it can tolerate growing in really rocky conditions with little soil because of its vining growth habit.

To me, this species doesn't smell too much like coconut unless it's been well taken care of. It smells much more like "chemicals" (the best way I can describe it; it doesn't really smell like any kind of fruit or vegetable or nut). When the plant is happiest, it smells almost exactly like coconut-scented sunscreen (which doesn't actually smell all that much like coconut, but certainly smells like tropical beach!). This is a great example of the properties of secondary compounds, or compounds produced by the plant that are not necessary for survival and often play a role in plant defences. When a plant is under stress, instead of spending a lot of energy making chemicals that it can store in leaves to deter herbivores, it will instead spend all of that energy doing basic metabolic processes like creating sugars and repairing tissues. Once the plant is no longer under stress, it will go back to producing secondary compounds as long as it has the energy to do so. This is a great example of allocation of resources, where the plant almost "decides" where it's best to use energy and what energetically-taxing activities should be avoided. Like me on a vacation: laying by the pool doesn't take a lot of energy so should be done often, walking or running takes a lot of energy so should be avoided :)

The leaves of this species look very similar to the common geranium, but aside from the smell there are a few differences that you can look out for. The first is the texture of the leaf. Instead of being thick and fleshy, this leaf is much thinner and "normal-looking" (which can be seen in the lower photograph where there's a leaf I just happened to catch straight-on from the edge of the leaf). Also, the upper surface of these leaves are completely smooth, unlike the furry upper surface of the common geranium leaf (which may actually vary in hairiness, depending on the cultivar, but will always have at least some hair on the upper surface). The lower surface of this leaf is where all of the glandular trichomes are located. The leaves of this species are also unique in their coloration, regardless of the maturity of the leaf. When very young, the leaf will be much darker green around the leaf veins than anywhere else on the leaf. As the leaf ages (from the middle picture to the bottom one), it becomes much more uniformly green but if you look closely you can still see a bit of a difference in "green-ness" in some areas of the leaf. The last difference with the leaves is the margin or the edge of the leaf. This is a comparison that actually should be avoided, however, as the margins of the leaves of the common geranium can look drastically different based on cultivar.

One of the most easily observed differences between these two species is the growth habit. This species almost entirely lacks a stem; instead there is a dense mass of tissue near the soil level that acts as a stem, and the leaves emerge directly from the level of the soil. All of the above-ground mass is composed purely of leaves. As the plant wants to explore more territory to find more resources, it will create underground rhizomes that will seek out pockets of soil to establish a new basal stem mass to grow new leaves. This rhizome can traverse rock surfaces if needed, and where it is above-ground it will look nearly black because of all of the melanin (yep, the same chemical that your skin makes as a result of skin damage; we refer to this melanin production as "getting a tan") that is produced in the rhizome. This acts as a UV protectant, and can prevent damage to the rhizome as a result of exposure to the sun. Deeply pigmented plant tissues are also generally avoided by herbivores, as digesting melanin is a difficult process and may actually be a toxic process to some insects. I have also tried chewing a leaf of this species, and also not an overly pleasant experience. Gives a much more "fuzzy tongue" experience, so I'm guessing this would suggest it would be toxic in smaller quantities to humans. It would still involve the consumption of a LOT of the plant to produce any kind of ill effects, but best to keep this one more out of the way of children if you can. On the bright side, the essential oils produced by this plant are much less irritating to the skin!

A cold-tolerant eucalypt

Species name: Eucalyptus gunnii

Common name: cider gum, eucalyptus

Location: Ontario

For anyone from Australia, to see any eucalyptus plant in Canada outdoors would probably be surprising. In fact, it's not just Australians that would be surprised; this Canadian was mighty surprised, too. I was shocked to see that the campus landscapers would have thought this plant was going to survive in our climate, which is inhospitable to tropical trees to say the least. To my surprise, the more I read about this plant the more I wanted to put one in my back yard for novelty sake; it's actually incredibly cold tolerant! This species of eucalyptus will readily survive winters with extended periods below -10 degrees Celsius, and can even survive short periods below -20 degrees Celsius. It's still not a good idea to trust this plant to a harsh Canadian winter, but finding out it could survive snow cover was a surprise to me. This is actually becoming a popular garden plant in Europe since it has the attractive evergreen foliage of a eucalyptus (and the incredible smell) while not having to be taken indoors every winter.

All eucalyptus trees are native to Australia and the surrounding area, but most have been successfully transported outside of this restricted area for ornamental and medicinal use. This particular species, the cider gum tree, is native to a very small area in Tasmania. Like Madagascar periwinkle (which you can read all about HERE), there are few individuals left in the wild in its native range, despite being so incredibly common in other locations in the world due to its ornamental value.

One spectacular morphological characteristic of this plant that is rarely seen to this degree in nature is the morphological variation of the leaves along a single branch. The leaves start off almost circular, with a very short (sometimes absent) petiole at the base of the leaf. The leaves spiral around the branches of the tree, and are a brilliant grey-green. As the branch grows longer, the leaves also elongate until they look very similar to willow leaves, and there is a change in colour so the leaves are a much darker, deeper green. If the tree is pruned into a shrub (as is most common in an ornamental plant setting), the shrub will retain its juvenile leaf form and never progress to having elongate leaves.

While this species of eucalyptus is not often used for anything other than as an ornamental plant, other species in the genus are used for their essential oils, which are very powerful antibacterial chemicals, insecticides, and even industrial solvents. The oils are sometimes also added to food, but only in very minute quantities (the saying "a little goes a long way" is absolutely true in the case of this plant, but also even moderate amounts of the essential oil when consumed is toxic to humans). The tree's leaves are the main food source of the koala, an animal often regarded as the "icon of Australia". Eucalyptus trees are also known as "water-suckers" since they can completely dry up a swampy area in only a few years, turning the soil into arable land. This doesn't last long, however, and the land quickly converts to desert after only a few growing seasons. The wood of eucalyptus trees is very quickly produced, and so it was once considered as a biofuel before being abandoned for other crops that were easier to care for.

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!

When is a Pelargonium actually a geranium?

Species name: Pelargonium x hortorum

Common name: Geranium

Location: Ontario

The geranium is one of the few ornamental plants in North America that is native to southern Africa. There are about 200 different species in the genus Pelargonium, and about 500 different cultivars of P. x hortorum alone. There is an enormous amount of variation in this one group of plants, thanks to the ongoing need for humans to have "pretty gardens." Ironically, this need for personal garden beauty has put almost every species in the genus at risk of becoming threatened in the wild, while the ornamental cultivars are at risk of becoming invasive in some areas!

This group of plants is a fantastic example of why you should never rely on common names alone to identify plants. There is actually a genus of plants called Geranium (which I have previously blogged about HERE). To further complicate things, North Americans sometimes refer to the Pelargonium geranium is "storksbills", while Europeans refer to the Geranium geranium as "storksbills." And just to make it even more fun, there is yet another group of plants in Europe referred to as "cranesbills" since they look like the beak of a crane when in flower--and Europeans refer to storks as cranes and cranes as storks. I feel a headache coming on. Does anyone else?!

There are about 20 species of Pelargonium that have very unusual scented leaves, and this property of the leaves has been exploited in cultivars around the world. You can probably tell from the second photo, the petioles of the leaves, the underside of the blade of the leaf, and the stems of the geranium plant are all very hairy. They're completely covered in small plant hairs called trichomes, and the role of these trichomes is mainly for plant defence. They're like microscopic daggers that the plant can use to deter herbivores. Sometimes some plants take this one step further and make modified trichomes that have oil glands at the ends. This oil usually has some sort of very potent smell, which helps deter herbivores when they brush up against the plant. If a plant smells very strongly of any odour, it usually means to stay away. If the herbivore doesn't get it, the oil is usually toxic and kills (or severely damages) the herbivore. Some plant essential oils in concentrated form are so potent that they can paralyze a deer if it consumes only a single leaf! In the geranium, the essential oils smell like other very common scents; everything from oranges to roses and everything in between (there are recognized species that have leaves that smell like almond, apple, coconut, lemon, nutmeg, allspice, old spice, peppermint, rose, southernwood, strawberry, and "fire"). This has been used in various ways to create cultivars with flowers that smell like one scent, and leaves that smell like another. We humans can do some marvellous things when it comes to plant breeding!

Aside from ornamental use, the essential oils of the geranium plant are used quite frequently in the perfume industry, often as a cheap substitute for rose oil. If you buy expensive rose oil perfume, make sure you're getting the right stuff! Also, the common geranium is edible, although I have tried it and it's not very tasty. I would recommend you stick to spinach if you want something green and leafy. If it's edible flowers you want (to decorate a cake or cupcakes), geraniums are a good choice.

Let's play a game: ID this plant!

UPDATE: The general consensus reached for the ID of this plant is Thymus pulegioides. This ID still doesn't feel right to me, but since I'm not a plant expert and the two that both came up with this ID are, I'm going to defer on their expertise and say that's what it is. At least, something close. The common name of this plant is broad-leaved thyme and sometimes lemon thyme (although, that common name is applied to just about any plant that looks like thyme that smells even remotely lemony, which is 5 or 6 different species). Thanks for playing, everyone! And thanks for Sophie and Matthew for the help via Twitter.

Species name: Lamiaceae sp.

Common name: plant in the mint family

Location: Ontario

I've been toying with the identification of this plant for a few days now, and I just can't seem to get it right. So instead of me identifying it, I'm opening the floor. Know what this plant is? Drop me a line in the comments section!

Instead of talking all about one particular species, I figured I'd talk about at least what I know for sure to be true: this plant is most definitely in the mint family, or the Lamiaceae. There are two major distinguishing features for this family. The first are the flowers: the petals are fused at the base into a tube-like structure, and at the end are modified into a large top petal and an even larger bottom petal. Sometimes, as in this example, the bottom petal retains morphological characters that would lead you to believe it came from the fusion of three petals (which it did) in the form of lobes on the petal edge. The second major feature that leads me to the general identification of this being a plant that's a member of the Lamiaceae is pointed out by the arrow in the bottom photo, the square stem. If a plant is in the mint family, it has a square stem. For some species, you have to use your imagination a bit more than others for how this rough round shape is actually a square, but more often than not the stem is a clear square shape in cross-section.

The leaves of this plant are smooth on both the top and bottom surface, and the leaves are incredibly small and lack teeth, all unusual characters for the mint family. One of the reasons why members of this plant family are so aromatic when the leaves are crushed is because of the tiny hairs on either the upper or lower surface of the leaves (or sometimes both) called trichomes that have a tiny oil droplet at the tip. This oil droplet is meant to deter herbivores, since in large amounts they taste downright nasty, and in fact most are carcinogenic. You don't have to worry about getting cancer from basil or oregano, though! Since humans are so large, you would literally have to eat a pound of basil a day for the chemicals in the essential oils to have any negative effect. The very reason why we started to use herbs and spices in food is to exploit these essential oils, which even in small amounts have very potent antimicrobial effects, and to kill food-borne bacteria before consuming food prior to refrigeration.