Monday, June 22, 2015

Canadian thistle

 Canadian thistle is one of my least favorite weeds.

Canadian thistle (Cirsium arvense) is Canada's revenge for US television programming.

One of my Canadian friends took issue with this statement.  He thought I was denigrating Canada's good name.  He told me that Canadian thistle was originally from Europe.  In response I pointed out that so were most of the ancestors of the people who made US programming decisions.

Some weeds have redeeming values.  Milkweed and nettles produce edible greens.  Milkweed is an excellent nectar source and is the larval food for Monarch Butterflies.

Other weeds are polite.  They say, "Oh, so sorry.  I did not know this was reserved parking."  They roll over and die when sprayed.  Burdock and Bull thistles fall into this catagory.

But not Canadian thistle.  Nope.  Virtually no redeeming value and very hard to kill.


Canadian thistle exhibits several characteristics that combine to make this an extremely resilient plant.

Thorns make it nearly impervious to control-by-grazing.

The waxy coating on the leaves resists wetting, making it difficult to thoroughly coat the plant with herbicide.

The plant produces prodigious amounts of seeds that the wind can blow for miles.  You can extinguish the weed on your property....and it will blow back in on the wind that very same year.

The plant also spreads by rhizomes.  It sends up shoots from the roots.  Those shoots have many latent buds at ground level.  Cutting, mowing or even desperate animals grazing the plants trigger the Hydra effect, every cut end produces two or more shoots.  In retrospect, one must wonder if the the Lernaean Hydra myth arose from frustrated shepherds in ancient Greece as they attempted to eradicate Canadian thistle from their pastures.

Canadian thistle mastered the art of invisibility, like two Deacons who accidentally meet in the beer aisle.  Bull thistles and burdock announce their presence with the subtlety of a teenager flipping the bird. Canadian thistle, in contrast, is a shorter plant and its hues are an exact match for bluegrass and tall fescue. 

The cornerstone to Canadian thistle's resilience is its root system.  A big patch of Canadian thistle is usually one plant (clone) held together by a massive, interconnecting system of rhizomes (roots).

Herbicides like 2,4-D function by mimicking growth regulators. The plant translocates the herbicide and every cell that is capable of division goes into uncontrolled growth.  Death results from total depletion of resources.  A contributing factor is that the uncontrolled growth causes the vascular system to get clogged with unorganized masses of growing tissue to the detriment of the plant's economy.  Think of it as ZIRP in the plant kingdom.

Canadian thistle can even survive this.  The clogging of the vascular system has a cauterizing effect that limits the amount of herbicide that translocates to the roots.  The roots have ample supplies of food and simply throw up more shoots.  The shoots are not as vigorous as if they had been mowed...but come they do.

Control plan

The best time to find the Canadian thistle is immediately after grazing animals leave the paddock.  The animals eat down the surrounding vegetation and leave the thistles.  You still will not see every one of the shoots but you can find most of them.

Every grazing rotation, walk the paddock and spray the Canadian thistle with a stout mixture of 2,4-D.  I like to amend my spray water with pH reducer to bind the hard water cations before adding the 2,4-D.  This step is less necessary when using the ester formulation of 2,4-D but the low pH also helps the herbicide penetrate the leaf surface.  I also add a goodly squirt of dish detergent to help the liquid wet-out the foliage. 

Note:  Glyphosate will knock back the Canadian thistle but it also kills off the grass.  The Canadian thistle comes roaring back when it does not have to compete with grass. 2,4-D only kills broadleaf plants.

Wet out both sides of every shoot.

Time the spray so the spray will quickly evaporate.  Pick a time window when it will not rain for 24 hours (or more).

Eradicating Canadian thistle entails a sustained effort and endless vigilance.  It requires the tenacity of an  adult.  One does not massacre Canadian thistle so much as grind them to a standstill.

Don't just complain.  Learn something!

In purely objective terms, Canadian thistle is admirable.  It not only survives, it thrives even in places where it is not welcome.  Is there any better definition of resilience?

So how might the attributes listed above "look like" in human beings?

Thorns:  Be protective of your personal space.  You should not be "vulnerable " and "intimate"  except to a few, proven confidants.

Waxy coating:  Exercise discernment about what you watch, read and the internet sites you visit.  Keep your mind and your life untainted by the garbage.  Remember, it is almost impossible to wade through barn-yard mud without getting shit on your boots...and tracking it into the house.

Seeds:  Share your knowledge.  Share your beliefs.  Help young people get started.  The seeds of Canadian thistle are quite small but there are a lot of them.  It does not take much of a push to change the direction of a rock when it is in a state of precarious balance.  The only way to find those rocks is to give a bunch of them a slight nudge.

Latent buds:  Have a re-start plan.  Save your extra seeds.  Give things away.  There may come a time when it will be given back to you.

The art of invisibility:   We announce who we are by the clothes we wear, the jewelry and tattoos we display, the vehicles we drive and the homes we choose to live in.  Invisibility happens when we do not "make a statement" with any of these.  Invisibility is a benefit that happens for free when we do not push the envelop or repeatedly and flagrantly violate the local norms.   In some places invisibility requires that a person wear a three piece suit.  In other places it might require costuming in Carhartts, camo or sports themed regalia.  In nearly all cases it means avoiding "biggest", "best", "newest","brightest" and "most expensive".

Massive interconnecting system of rhizomes: Those rhizomes are really banks and buffers.  They store food.  They dilute shocks.  A critical distinction that must be emphasized is that the National Bank of Canadian thistle focuses on collecting deposits from the mature shoots and investing those assets in the conquest of uncolonized areas.  This is the exact opposite of the model where asset flows are primarily used to prop up "entitlements".  The two models resemble each other superficially.  The critical difference is that the direction of asset flow...they are almost mirror images of each other...identical but opposite.

This dovetails with the art of invisibility.  If Bull thistles are the neighbor with a $75,000 Sport-Utility vehicle and negative net assets, Canadian thistles are  the neighbor driving a $6000 Chevy and have a net worth of half a million dollars.

Cauterizing effect:  The Canadian thistle clone has the ability to abandon any individual shoot.  It has an exit strategy.  As humans, we must recognize that circumstances will occur that make it advisable to separate from friends, jobs, homes, hobbies and social organizations.  Societally, we should accept that it is necessary to abandon well intended but perversely consequenced efforts.  Affirmative Action, Affordable Care Act, No Child Left Behind, Subsidized housing and the War on Poverty come to mind.  The question should not be "How many more times can we double-down before it will succeed?" but, "How cheaply can we cauterize the wound and how quickly can we redeploy the assets?"


  1. Aahh...those poor little children at the Lucky_P household spent many a summer morning on thistle patrol...cutting off and collecting flowers, spraying with 2,4-D, and digging/pulling them from the pastures. Character-building work, you know... It took years, but they virtually eradicated them from the farm... think I've pulled less than a dozen this year, on 110 acres of pasture, and have ... so far as I can ascertain... managed to keep all from going to seed. But... there will always be some here, because the neighbor next door does not control them - though I've been known to hop the fence and decapitate/uproot those within close proximity to my fenceline.

    1. It does build character!

      My oldest daughter enjoyed doing thistle patrol. Now 25, she recently confided it was because she liked swinging the machete (a Blackie Collins, 21" model) and watching the heads fly off.

      BTW, congrats on purging thistle from your pastures.

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