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!

To Zing or not to Zing, that is the question

Species name: Zingiber officinale

Common name: ginger

Location: teaching lab at Western

Ginger is one of the most commonly used spices around the world, and one that many, many people love the taste of (you can count me as a non-member of that group; I personally HATE ginger). It is a tropical spice (and hence why it's a spice and not an herb), and is now most commonly grown for export in India, China, the Philippines, and Jamaica. There are many other countries that grow a lot of ginger, but those are countries that also use a lot of ginger in their traditional cooking (Nepal, Nigeria, Cameroon, Thailand and Bangladesh) and so only a small amount of the total harvest would be available for export. Despite being one of the most commonly cultivated spices around the world, very little is known about the wild populations of this species of ginger (there are four other species in the genus that are commercially sold as "wild ginger," but be careful; the native Canadian species known as wild ginger, an unrelated species to this group, contains potent carcinogens and should never be consumed) throughout its native range in southern Asia around Thailand and Indonesia. There is the presumption, however, that the population sizes are declining due to habitat loss.

Ginger was once believed to be closely related to grasses but now has its own order, the Zingiberales, within the group known as Commenlinids. These are a unique grouping of species within the monocots that includes all grasses, bananas and their close relatives, spiderworts, water hyacinths, and the palms. Quite a diverse group of plants, and a group that most people probably never would have assumed went together. I don't know about you, but water hyacinths (popular ornamental pond aquatic plants with a large bulbous "bladder" at the bottom of the leaves to keep them afloat) and palm trees don't belong in the same group of plants in my mind! But when we compare DNA sequences, these groups of plants do, in fact, make a genetically related group called a monophyletic group. Pretty neat what DNA sequence analysis can show us! Is there something, other than DNA sequences, that demonstrate that these seemingly drastically different plants belong in the same group? Well now that we know they belong, we do actually notice some biochemical similarities between these plants. The most striking of these similarities is the production and storage of ferulic acid in the cell walls of the plant tissues. This type of acid is only produced in this group of plants, and the best part about ferrulic acid? It glows under UV-light. Granted, it is produced in such low quantities that even if you put a grass plant or a palm tree under UV-light you wouldn't notice it glowing but this acid can be extracted and concentrated and used to make things glow. Pretty neat! Ginger plants do share many characteristics with grasses, so I can definitely see why it was assumed they must be very close relatives. They both have the same morphological features with leaf growth and development as grasses: the leaf sheath wraps around the stem (and the stem is actually just composed of concentric leaf sheaths that grow inside one another), forms something called a ligule at the top of the sheath that helps prevent the plant from plant diseases (it acts almost like a piece of tape that prevents anything from getting down between the sheath and the rest of the stem and can be seen clearly in the third photo from the top), and the leaf blade which is the "leafy floppy part" that comes off the stem. The most interesting part about ginger and grass leaves is that each species has its own ligule; they're almost like identification "fingerprints" that can be used by botanists to determine species. Pretty neat that no two species have identical ligules.

If you're an avid reader of my blog (which you should be if you aren't!), you'll have noticed something right away, before barely scrolling past the pictures. The last name of this plant, "officinale," must mean it has medicinal properties! If you assumed that, you would be correct. Common ginger has been used for thousands of years as a medicinal plant, reportedly being able to treat anything from dyspepsia to constipation and colic. Modern scientific research today shows that the rhizome of the plant contains a group of chemicals called gingerols, and these chemicals stimulate the digestive system and cause an increased amount of motility of the gastrointestinal tract. Ginger extracts would definitely help with mild indigestion or mild cases of constipation, but more severe gastrointestinal diseases or disorders have not yet been evaluated for efficacy. There has also been a lot of use of ginger in treating muscle pain associated with intense physical exercise (consumed in China during times of intense building in the 1200s to 1800s, and trekking for materials for these construction projects) and arthritis, and this has also been shown to be somewhat effective in clinical trials. When ginger extract is consumed after a workout, muscle pain post-workout can be reduced by as much as 25%. The catch: ginger extract must be consumed daily, workout or no workout, in order for this effect to be noted. In Canada and the United States, ginger and ginger extracts have made it onto the coveted "generally regarded as safe" lists. So does this mean that ginger is completely safe? Well, like all herbal remedies, you should always check with your doctor before taking them. Ginger in particular causes an increase in bile production as a way of promoting faster digestion. This isn't a problem for most people, but those most sensitive to an increase in bile production will report having heart burn after eating ginger. In cases where someone is sensitive to bile in that they commonly get gall stones, eating ginger every day or taking pills of ginger extracts would be really silly because it would exacerbate the problem. Those with ulcers or inflammatory bowel disease may react badly to large amounts of ginger because of the increased stimulation of the digestive tract, but these reactions are rarely enough to land the person in the hospital (but are unpleasant enough that it is rarely done a second time!).

Despite ginger being such an important plant to many countries around the world, it has yet to make it onto any kind of "national or state/provincial plant" list. This is really too bad for ginger; people who only appreciate ginger for its flavourful rhizome will never get to fully experience the greatness that is ginger. The flowers are absolutely stunning to look at (so delicate and almost transparent the tissue is so delicate, hence my difficulty photographing them), but also could practically knock you over with their intense sweet scent. The flowers open in the evening to attract their nocturnal pollinators, and then are wilted and shrivelled before the evening of the following day.