Friday, August 24, 2012

The Northern Agave: the Yucca

Species name: Yucca filamentosa

Common name: Adam's needle, filament yucca

Location: Ontario

This is one of those rare plants that is not in my garden at home, that is native to eastern North America, and that I absolutely LOVE. In fact, I used to love this plant purely based on the fact that it reminds me of Agave (which you can read all about HERE; it's actually a close relative in the same family) and has such a tropical feel, yet is fully cold hardy. Not only are the flowers absolutely stunning and smell fantastic (they're all past their prime by the time I got around to photographing this plant on campus), they also open at night and are the most fragrant when it's dark out. This phenomenon is not uncommon in the plant world, and is referred to as being a "nyctinastic" plant. Since this is such a fantastic plant, the people of New Mexico have recognized it as their State flower. Way to go, New Mexico!

One of the main reasons why a plant would want to open its flowers at night and release most of the scent of the flower at night is to attract nocturnal pollinators. In this case, there is only one main pollinator of the Yucca, called the yucca moth. Due to habitat destruction (they prefer rocky deserts, sandy areas, dry prairies, and light woodlands, all habitats that are being lost in North America at an alarming rate) this plant is becoming more and more rare, which also means the yucca moth is becoming more and more rare. The yucca moth doesn't just get food from this plant, it also uses the plant to house its eggs and larvae until they are ready to moult into caterpillars. The moth lays its eggs at the base of the flower on the inside so that it is enveloped by the developing fruit. As the larvae hatch, they consume some of the nutrient-rich seeds before exiting the seed pod when it splits open naturally (when the plant is ready to release the seeds). So why would a plant "agree" (plants aren't capable of conscious thought, so to say they "agree" to do anything is inflicting a bit of a human-centric bias onto a plant) to have its seeds, its babies, consumed by an animal? Well, if all of the seeds produced developed into offspring, the young seedlings probably would not be able to compete for resources sufficiently with the already established parents, and there would be too much competition between them. So the parent Yucca allows the relationship between the moth and the seeds to occur to prune out the number of possible offspring and gaining the benefits of cross-pollination provided by the adult moth. A great system! The larvae in return ensure they do not eat all the seeds, and there are still plenty around to ensure population replacement at the very least, and population growth during good years. How the larvae "know" how many seeds to leave I don't think is fully understood, since larvae of any species are incredible eaters and can eat many hundreds of times their body weight in plant material before they moult into adults.

The uses of this plant are numerous, the least of which today being for textile use. The strikingly tall inflorescence stalks have long fibres in them that can be spun to make (incredibly uncomfortable) clothing, textiles, or rope. Yucca flowers are also edible, and are a deep-fried delicacy in some southern states in the US. Some species of the genus also have edible fruits, but this species isn't one of them since the fruit walls are made up of very tough plant tissue. The leaves of this plant are also sometimes referred to as "meat hangers" since they are so tough they can pierce meat and can be knotted together to make a ring that can be hung on a tree branch to dry cured meat.

The most important use of this plant even today is as a fish stun agent. This might sound a little strange, and why would you want to stun a fish, anyway? Well, it makes them a whole lot easier to catch! The traditional way to stun fish with this plant is to take either chopped up leaves or roots (or both, just to be sure) and boil them in water for an extended period. Then take rocks and macerate the tissue, extruding all of the juices that come with the macerated tissue. Those juices, along with the cooking water, are then dumped into streams and small ponds with high densities of fish. The juices contain fish toxins that either instantly paralyze (or kill if not collected immediately) the fish, and they are scooped up and either used as bait fish (if they're small) or cooked and eaten (if larger). The most interesting part of this story is that this is probably the method used to catch the original fish used in the first fish farming processes thousands of years ago! Once the stunned fish are put into fresh water (ideally, an isolated pond near the settlement), the effect gradually wears off and the fish return to normal. The effect of the fish stun, however, remains in the original body of water until it can be appropriately flushed out through natural processes (dilution, breakdown by other organisms like bacteria, flushing further down the watershed, absorption and depletion in the soil, etc.) so using this plant to stun fish for fun can be incredibly detrimental to an ecosystem not just immediately, but potentially for many months or years to come!