Monday, June 25, 2012

Recommended reading -- Weeds

“Beware the triffids ... they grow ... know ... walk ... talk ...stalk ... and KILL!”
Movie poster for The Day of the Triffids, 1963.
Weeds have a bad reputation.  They invade gardens, croplands and wildlands, and we dig, pull and spray in response, often at great expense.  They can inspire a fear almost as great as the terror of the triffids -- those genetically-modified plants (in 1963!) that stalked, stung and killed people, and then ate them.  Last week I found the dreaded field bindweed in my garden.  I dug deep in pursuit of its insidious root system, and burned the whole lot in the wood stove.
Field bindweed aka creeping jenny, Convolvulus arvensis.  Photo by Bouba.
Is this level of anxiety justified?  Not always.  Weeds are wrapped up in a tangle of definitions, values and judgements that change with time and human taste.  Richard Mabey provides an interesting and entertaining account of it all in Weeds: in Defense of Nature’s Most Unloved Plants (2010).

Weeds often are defined simply as undesirable plants, but “undesirable” is a matter of context.  Furthermore, in some contexts the marvelous adaptations of weeds can benefit humans -- their prolific offspring, able to travel far and wide, means that something will be growing almost everywhere.

Left: ivy-leaved toadflax, Cymbalaria muralis, has colonized a wall. Its nicknames speak to the ability of weeds to spread far and wide -- traveling-sailor, mother-of-thousands.  By SP-KP.

Below:  vervain (Verbena bracteata, left) and knotweed (Polygonum sp.) take advantage of open habitat in asphalt.  The vervain's leaves are about 5mm across.
Knotweed, tumbleweed and kochia weed, bane of my garden, grow in profusion just upwind of our neighborhood where the State recently “improved” the grounds around the Territorial Prison.  We would miss them if they weren't there.  Like many weeds, they colonize disturbed sites, hold the soil in place, and keep it from turning to dust in the wind.  For this I am grateful though I regularly chase tumbleweeds from my yard.

As Mabey repeatedly points out, a weed to one person or in one place or at one time can be a treasure in a different setting.  His examples are fascinating.  Most memorable are the trench gardens of World War I.  Soldiers used scraps of battle debris to fence small plots where they transplanted weeds from nearby fields.  And of course there were the poppies:
“Red poppies, and a blue flower, great masses of them, stretched for miles and miles.  The sky was a pure dark blue, and the whole air, up to a height of about forty feet, thick with white butterflies.  It was like an enchanted land; but in the place of faeries, there were thousands of little white crosses ...” William Orpen, An Onlooker in France 1917-1919
“We are the dead.  Short days ago we lived, felt dawn, saw sunset glow ...”
From In Flanders Fields by John McCrae.  Photo source unknown.

Archeological evidence and paleoenvironmental reconstruction show that plants always have moved around in response to change, and Mabey includes detailed accounts of specific comings and goings of weedy plants.  Might these traveling plants play a helpful role in the face of climate change?  Today’s newcomers, though unwanted at present, may be the first arrivals of vegetation that will support us in a warmer world.

Weeds are not a simple issue, as the author makes clear. While some are obvious threats, others should be addressed with reason rather than reaction.  Is it reasonable to douse them with broadcast herbicides year after year, especially when we're making little or no progress in the battle?

This book focuses on Britain and Europe, with less coverage of weeds elsewhere.  Mabey acknowledges the wide variation in weed danger across the world.  It is much worse on isolated land masses such as Australia and Hawaii, whereas other ecosystems, such as his own, appear to be more resilient or resistant to invasion.

Also reflective of the author's background is the abundant British English, which made me scratch my head at times but never enough to detract from the wonderful reading.  And my vocabulary has expanded ... now I know a verge when I see one!

verge |vərj| noun
Brit. a grass edging such as that by the side of a road or path.
(Oxford American Dictionaries)
Dandelion, sow thistle, evening primrose, yellow sweet clover and kochia weed
spread out from the verge, intent on taking back the streets.

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