A Rocky Mountain Juniper

Species name: Juniperus scopulorum

Common name: Rocky Mountain juniper

Location: Ontario

As the name suggests, the Rocky Mountain juniper is native to the Rocky Mountains in North America, from British Columbia all the way south into Mexico (although, there are so few populations left in Texas and Mexico that the range should probably be amended to say it ends in Arizona; this very suggestion has been put forth by the USDA more than once). It thrives in high altitudes where it is common and a relatively short tree (as most alpine species are), but incredibly long lived. In New Mexico, one was felled that was estimated to be 1,500 years old, and a standing dead tree was found to have 1,888 tree rings. There are some individuals left in Arizona that are estimated to be 2,000 years old or more. Incredibly enough, these aren't even the oldest living trees on Earth...

Those of you who live on the west coast and have seen this species in their native habitat on mountain sides will probably be pretty jealous of the height of this individual on campus. It was probably planted when Talbot College was built in about 1970, so the tree would only be 40-50 years old. It's already much taller at 50 years than other individuals would be after 750 years or more! Just goes to show that when you plant species outside of their native habitats, strange morphologies can be achieved.

Like all gymnosperms, the "berries" produced on the branches are not fruits, no matter how they might appear. Gymnosperms, unlike angiosperms, do not have flowers and so don't have all the layers of tissue required to produce a true fruit. Despite this fact, ginkgo (which you can read about HERE), yews (which you can read all about HERE and HERE), and junipers all produce berry-like "fruits" that are just modified seeds. The outermost layer of the seed is modified to store starchy and sugary compounds, often with a lot of waxes and resins to protect the seeds from predation by small animals, and are produced instead of cones. Another interesting fact to note about this species of juniper is that, like ginkgo and holly, the tree is either male or female but never both. The bright blue modified seeds are produced on the female trees, and the male trees have pollen cones that are produced in the spring and release all of their pollen into the air right around spring allergy season. It seems like in the spring and fall, all of the trees conspire against humans to irritate our airways! Sometimes the blue berries are produced regardless of whether the male tree is present or not, but the seeds inside will not be viable. Like holly and ginkgo plants, if you want to ensure the success of the seeds you need to plant both sexes in close proximity.

Many junipers have traditionally held a strong importance in the lives of native North Americans due to their medicinal value. The bark of the Rocky Mountain juniper is boiled to make a tea and consumed to treat coughs and fevers. Since there are so many resins produced by this species (the yellow "sap" that drips down the outside of the tree, especially after the tree has been wounded) have great antimicrobial properties, and are actually the very reason the tree produces them in the first place! I have strong suspicions that any time the bark of a gymnosperm is cooked to extract the resins then consumed, it will have a strong effect against bacteria in the mouth and throat. This doesn't mean you should attempt this, however; some resins produced by various species of gymnosperms are highly toxic and should never be consumed! It's always a fine line in herbal medicine between things that will make you very ill and things that will help your sickness. Mixing your own concoctions just to try things out is strongly discouraged.

The Japanese can't make their own taxol from their yew

Species name: Taxus cuspidata

Common name: Japanese yew

Location: Ontario

You might be wondering why I'm featuring the same plant twice in the same week, but you would have made one vital assumption that is incorrect: just because two species look the same doesn't mean they are the same. The Japanese yew, featured here (native to Japan, as you might have guessed), is a very close relative to the Canada yew, featured in my blog post on Monday (read all about it HERE). In fact, by assuming that the photos above represented the same species as that of the Canada yew, you would be making the same error that many botanists have made in the past; it was only recently demonstrated that there are distinct species within the genus Taxus. The genus was originally thought to be monotypic, and instead having distinct geographic races or subspecies that are on their way to becoming their own species, but have not yet become distinct enough to warrant the title. The Sumatran and the Mexican yews are the most different from the type species, the European yew. These were the first to obtain their own species designation, with every other species following suit and being confirmed through DNA sequencing.

So if these species are so morphologically similar, how do you tell them apart? Well, the needles and their arrangement on the branches is the first clue. The needles of the Canada yew are arranged around the branches when young, but the development of the bark on the branches almost flattens out the arrangement of the needles as it matures. If you look at the branches that are brown in colour instead of green (showing that bark has been formed), the needles are in two rows on each side, but are flattened on the branch. It has almost become two-dimensional. The difference in the maturation of the Japanese yew branches is that the needles remain spirally-arranged on the branch; they never flatten out unless something has been grazing the branches. With age, the needles also turn upwards, so all of the oldest needles on the inside of the shrub or small tree are pointing upwards, even though their point of attachment on the branch is all the way around it.

The second hint that these are different species is their sheer size difference. The Canada yew barely reaches a height of 2 meters off the ground and completely lacks a central stem. While the Japanese yew pictured above doesn't really look like it has a central stem, it is clearly more "tree-like", and the branches have the ability to support their own weight as opposed to drooping onto the ground like the Canada yew branches do. The Japanese yew can also grow to a maximum height of 18 meters.

The last major differences are not visible to the eye, but rather "visible" to a machine called a gas chromatography mass spectrophotometer, or GCMS. These machines are also sometimes called the "mass spec," and if you watch CSI at all you will have heard of them! They really do exist, and they are used in much the same way as suggested on TV (but not nearly as quickly, and the results are a bit harder to interpret than what the shows make them out to be!). You dissolve a bit of an unknown substance into a solvent (usually some sort of alcohol, although other organic solutions are sometimes used like chloroform), and inject a very small quantity into the machine. The machine separates the individual components of the liquid mixture by molecular size, and displays a graph of molecular weight versus abundance. The shape of the peak tells you what types of chemical bonds are present, and the location along the size axis tell you how big the molecules are. The height of the peaks tell you how much of any given substance are present. So what does this have to do with the Japanese yew? Well, it's a rather unfortunate tale for the Japanese; if they want to make their own paclitaxel, they're going to have to start planting Canada yew. The Japanese yew doesn't contain the right combination of taxanes to have the desired medical effects. In fact, the Japanese yew is exponentially more toxic than the Canada yew; it has the distinction of being the "Japanese horse killer." Just five needles are enough to kill a small dog. If you choose to plant this ornamental tree in your garden, please keep animals and small children away from it! And don't EVER use it as a Christmas tree!

Taxol in plant form

Species name: Taxus canadensis

Common name: Canada Yew

Location: Ontario

The Canada yew is an incredibly important shrub to people all over the world, and most don't even realize it. While technically not a tree, most of its closest relatives can be up to 25 meters high. The Canada yew has no main trunk, and so just kind of flops onto the ground. It was originally thought to be a subspecies of the English yew, Taxus baccata, but was shown to be a distinct species through DNA sequencing and actually more closely related to the Western yew than the English yew! Just goes to show that plants that appear to be closely related based on morphology alone might be misleading you when it comes to their genetic relatedness.

The Pacific or Western yew has just recently been downgraded from threatened to nearly threatened on the IUCN's Red List of endangered and threatened species worldwide. Its eastern relative, the Canada yew, has now replaced the Western yew as a commercial shrub. So why the need to produce it commercially? Well, it is an incredibly attractive plant with its red arils and soft green needles. The arils of these plants, contrary to what they look like, are not fruits! Yes, they're soft and fleshy and contain a seed. But because conifers cannot produce fruits because they do not have flowers, the red arils can't possibly be fruits. Instead they're just highly modified seed coats, which have been modified to store sugars and other tasty things that are attractive to birds and small mammals. Unfortunately, these red arils are also attractive to children and lead to quite a few deaths or hospitalizations every year since the seeds are incredibly toxic. The animals that consume the yew arils only eat the fleshy outsides, and either swallow the seeds whole and pass them right through their digestive tract, or leave the black seeds behind.

Sure, the ornamental use of this plant is quite important in Canadian industry. But that's certainly not the most important use of this plant worldwide. In the late 1980s and early 1990s, this plant was discovered to have a unique set of chemicals called taxanes with an incredibly important role in human health: they kill cancer cells. The chemicals were first isolated in 1992, and lead to the widespread population decline of the Pacific yew in western Canada. The Canada yew in the east was then discovered to have just as high a concentration of taxanes that were just as easily purified from the bark, and this species is much more abundant. It can also be sustainably harvested every 5 or so years, and so the purification of taxanes was switched to the bark of the Canada yew. Once the process was perfected and clinical trials were completed, drugs were officially put into production; worldwide they're called paclitaxel (the generic name) or taxol (the brand name). These two drugs are now the most widely prescribed anti-cancer drugs around the world. The other reason why this is so significant? The research was done at the university that I currently attend, The University of Western Ontario in London. Hometown pride! While there are still some stands of the Canada yew being used for taxane production, some of these chemicals have been successfully synthesized in the lab. It's only a matter of time before the entire spectrum of taxanes can be artificially lab-created and so wild populations of both species can be left to their own devices.

The medicinal use of the Canada yew doesn't stop there, but any medicinal use of this plant is incredibly dangerous because it is deadly toxic. Native North Americans used the young tips of this plant in very small amounts steeped in tea and consumed to alleviate rheumatism. There is some clinical evidence that consumption of this plant is effective in this way for rheumatism, but it is a very fine line between an appropriate medical dose and a lethal or very toxic one. For this reason, most doctors (and even herbalists) prefer other routes of relief.