Positive Poison

(Written by undergraduate student guest blogger from Byrne seminar Fall 2014 at Rutgers)

Ask any Boy Scout, backpacker, hiker, or avid outdoorsman what plant they’re most wary of, and the majority will give you the same answer: poison ivy.  Toxicodendron radicans, more commonly known as poison ivy, is a flowering plant found in North America and Asia.  It is well known for the itching, irritating, and occasionally painful rash contact causes in most people.  This reaction is caused by urushiol, a clear liquid in the sap of the plant, which, contrary to popular belief, serves not as a defense mechanism but as a way to help the plant retain water.  Because of the reaction it causes, poison ivy has gained a rather negative reputation in the eyes of most people.  Various mnemonic devices, such as “leaflets three, let it be”, have been coined to help in identifying and avoiding it. There’s even a super villain from the Batman comics named after it. 

 copyright: Larry Korhnak (http://www.sfrc.ufl.edu/extension/4h/plants/Poison_ivy/)

      Despite its negative effects on humans, poison ivy serves an important and beneficial role in the environment.  The poison ivy plant produces whitish, waxy berries that develop in the summer and persist into the winter, providing a food source for a variety of wildlife, including deer, squirrels, insects, and more than 60 species of birds.  Poison ivy is also very valuable to shoreline and coastal areas where, due to its salt tolerance and ability to grow in nutrient-poor soils, it plays an important role in preventing erosion and protecting sand dunes.  Several species of moths also use poison ivy plants to shelter their larvae while they pupate.

     So while poison ivy is considered a weed by most, it does have a positive side as well.  It just goes to show that even the most harmful and unwanted weeds can have their pluses. 

Recent weed-related articles in the media

Jane Kramer writes about her foraging adventures in Europe in The New Yorker article The Food at Our Feet.  On the New York Times blog City Room, they have a series in Urban Foraging by Ava Chin, writing about purslane picked from the sidewalks of the city, and much more.

Ecologists have started to argue scientifically about if alien species are necessarily bad or not. It started with an article in Nature (subscription only, so no link, but find it by googling 'doi:10.1038/474153a') by Mark Davis and 18 other ecologists.  This led to a bumper crop of protest letters from many other ecologists (see the issues afterwards in Nature), and it entered the popular media too.  Here is a podcast from Radio Australia about it. 

In an article in TIME magazine, Bryan Walsh ponders if 'In a Globalized World, Are Invasive Species a Thing of the Past?'

Wired adds to the pile, with 'Sometimes Invasive Species are Good'. Wired goes on to describe 9 invasive species worth admiring, including the dandelion weed.

Why We Must Learn to Love Weeds

On June 4, Wall Street Journal published an interesting, great and refreshing article on weeds by Richard Mabey, titled "Why We Must Learn to Love Weeds".  It highlights that what is a weed in one place can be a beloved plant in another, so the tag 'weed' depends on circumstances and not a specific species.  Houston in Texas, USA, has even tried to outlaw weeds, by making weeds illegal, in their law saying:

"the existence of weeds, brush, rubbish and all other objectionable, unsightly and unsanitary matter of whatever nature covering or partly covering the surface of any lots or parcels of real estate."

Think about that for a while.  You are outlawing plants that try to grow in or cover anything that humans have made.  That really sets up the fight, man vs. weed.  Since the only plants that can grow in many human-made environments are by definition weeds, this law declares war on a large branch on the Tree of Life. Is that what we want? Is that necessary?  And don't we have more important things to do than spraying pesticides in artificial environments were we live?

Richard Mabey continues:  

"All of these definitions view weeds entirely from a human perspective. They are plants that sabotage human plans. [...] But is it conceivable that they might also have a botanical, or at least an ecological, definition?"  

Maybe weeds follow us humans because we make places where these plants thrive?  Maybe we 'make' the weeds? I don't think there is a botanical definition that fits all weeds, but plants that lived in disturbed ecological habitats are certainly often weeds.  But even a definition as 'disturbed habitat' requires a human input, since soil disturbance due to a landslide, for example, would lead to a new succession in habitats with new pioneer plants, and not suddenly be seen as a weedy area.  I think the 'weed' definition is in the eye of the beholder, in us humans.

The article addresses further our view of weeds in our cultures, how they are symbolic of evil even in childrens' books like Harry Potter and science fiction.  How many of them have been or become useful plants for things like crops, medicine, or soil improvement. Weeds move around, and homogenizes an Earth we humans have changed and made less natural over the last centuries.

Richard Mabey really puts the weeds into a wider perspective in this article which is an excerpt from his new book (which I will have to get).  He ends his article:

"Weeds are, in this sense, paradoxical. Although they follow and are dependent on human activities, their cussedness and refusal to play by our rules makes them subversive—and the very essence of wildness."

So true! Every aspect of natural and human life you can find examples of in weeds, even politics. Read the article, it is excellent.