sarahkeenihan

When is a weed not a weed?

In April 2014 on April 15, 2014 at 3:22 pm

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A ScienceforLife.365 guest post by Dr Heather Bray* 

Heather: My garden needed a darn good weeding this morning. I spent a couple of hours on it, furiously pulling up or digging out the offenders, being careful not to disturb the plants I have nurtured since before the summer..

When it came to this little fellow however, I left him alone. I decided this one wasn’t a weed.

The best definition for a weed is the first one I learned in Year 7 Agriculture:

A weed is a plant in the wrong place.

We decide which plants are in the right place and which ones aren’t based on a whole range of factors; many of the reasons are based in science, but some are not. Some plants are dangerous and so we consider them weeds because they are toxic to humans or animals. Some weeds can affect nearby plants through competition for resources in the soils or by suppressing their growth through allelopathy. Some weeds are invasive and push out indigenous flora. Other weeds cause harm indirectly, and are considered a pest because their presence in association with other plants can reduce the purity, quality or price of an end product destined for market.

But some weeds are pretty, and so we choose to leave them where they are, or move them to another place and even help them to grow. Those of us who live in urban areas will be mostly familiar with this aesthetic idea of a weed as we arbitrarily decide whether a plant is in the right place to suit our own needs.

By some definitions, all the plants in my garden are weeds. The heartsease pictured above I spared quite simply because I like it. This particular one is an escapee, being self-sown from a plant in a pot.

I also have lots of arum lilies, the loveliest of all the weeds in my opinion. These remind me of the times I did practical work on dairy farms in NSW, where there were often clumps visible in the paddocks. All the ones I have now came from three lilies I brought from a previous garden, so I can see how they can ‘jump the fence’ and become a pest. There are also weedy tendencies in agapanthus, the species I used to re-establish the garden bed quickly (after the process of getting a new fence trashed what was previously growing).

I do feel a little guilty sometimes about both of these plant choices, but I’m planning on selling my house soon and needed something cheap, pretty and hard to kill. And they are everywhere in gardens around where I live. At least I haven’t planted lantana, a common Adelaide garden plant and ‘Weed of National Significance’ – I have vivid memories of seeing this species fill whole valleys of bushland in coastal NSW.

A weed is a wonderful example of something that is both a scientific concept and a social one. Ideas about what plants belong where can be constructed socially and culturally. There are others; for example ideas about food and naturalness are both influenced by factors other than science. It is important when we want to engage the community in discussions about scientific ideas that we don’t assume everyone will see things in the same way.

One person’s weed is another person’s flower, and so my little heartsease is safe … for now.

*You can find Heather on twitter as @heatherbray6

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  1. Reblogged this on Stuff & Things and commented:
    Here’s something I wrote for Science.365 …

  2. […] to free up time for my growing work commitments as a freelance science writer. Guest posts from Heather Bray, Geoff Hudson, Tiki Swain (here and here), Mia Cobb and Cameron Webb have also been wonderful, […]

  3. […] written be me but with fantastic guest contributions from Kirsti Abbott, Mia Cobb, Cameron Webb, Heather Bray, Tiki Swain, Geoff Hudson, Matthew Bowie and several […]

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