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What in Tar(weed)nation?! An Example of Working With Nature to “Beat” Weeds

This month we’re focusing on weeds an how to manage them. I’m including a lot of information about how livestock can manage your weeds for you by grazing them. But, while many weeds are perfect forage, not ever weed can be grazed. That’s when we need another approach, like this example from John Marble.

When it comes to weeds, I’m beginning to think that over the past few decades I’ve fallen into a bit of a rut – maybe even become a bit dogmatic. When someone asks me about weed issues, I typically respond with a short homily along the lines of,

“Well, if you are seeing more weeds, it must be because you are doing something to cause more weeds.”

Then I follow up with a set of questions designed to get at the truth of their failing:

How many paddocks do you have?
What is your rest period?
How much residual are you leaving?
What is your percentage of bare ground? Is it increasing or decreasing?

Why are these questions important? Well, more paddocks provide for longer rest periods. Longer rest periods and leaving plenty of residual keeps forages healthy and healthy forage is more competitive against invasive species. We also know that invaders are quick to take advantage of thin pasture stands and bare ground. And, of course, an increase in bare ground means that something isn’t quite right in the pasture equation. That could be management, or it could be a result of soil type, precipitation or some other environmental challenge.

More recently, I’ve begun to think that perhaps the world of weeds isn’t as simple as all that, mainly because, much as I hate to admit it, I have weeds – more weeds than last year, and more than the year before. Maybe I’m doing something wrong. Horrors!

A History of Managing Weediness Here on the Ranch

Over the past 30 years or so, I’ve come to a rather uneasy truce with most of the plants that folks around here call “weeds.” I eliminated a ton of weed problems by declaring “If a cow eats it, it’s not a weed.” This only leaves a few plants that are generally either poisonous, extremely invasive, or disruptive (for example, plants that prevent cattle from being able to graze.) My list of troublesome plants is actually pretty short:

Tansy Ragweed (poisonous, non-native and invasive)
Himalayan Blackberry (invasive, non-native and disruptive)
English Hawthorne (invasive, non-native and disruptive)

There are other plants that are not quite troublesome enough to make the list, mostly thistles of various stripe. In large part, their population can be limited through proper grazing management. Weed problems mostly solved.

Or maybe not.

Thanks to Rebecca Ozeran of University of California, Agriculture and Natural Resources, for this photo.

Three years ago I noticed a new weed, new to me anyway. Considering the fact that I’ve spent the past few decades looking pretty closely at pastures, new plants tend to pique my interest a bit. I pulled the new-comer from the ground and looked it over, then tossed it on the truck seat next me. Back home, I scanned through the weed book, quickly identifying it as some sort of sunflower: small yellow blossoms on a tall stalk. But flowers aside, there were two other characteristics that nailed it down: it smelled like paint thinner and the stem was sticky like…tar. The book said tarweed. Huh. Probably Madia sativa. I decided to file tarweed away with the thousands of other curiosities I find scattered around my ranch life.

A year later, tarweed was scattered over a fairly wide swath of the ranch. For the most part, it seemed to prefer poorly-drained, heavy clay soil; the worst pastures on the ranch. These were also the areas with the highest percentage of bare ground and large resident populations of pioneer species (aka “weeds”). These are also our most fragile soils. If we turn cattle out too early on these fields, they are prone to pugging.

Looking over a rapidly growing population of nasty, smelly, sticky weeds, I determined that I needed to do something different: change management, adapt, overcome. Eventually, I selected a new tactic to beat the tarweed: delay the onset of grazing, which should give the grass a better chance to out-compete the tarweed plants.

And so, this year, I delayed grazing those low-lying fields. April 1st came and went. May 1st too. On June 1st I looked across a sea of beautiful green grass, hardly a tarweed in sight. Success! The cows were marching along, due to arrive in the former tarweed paddocks in two weeks. On June 15th I drove past those same fields and was shocked to discover a sea of tall stems with millions of small yellow blossoms. The tarweed had returned with a vengeance, crowding the field at perhaps ten times the number of plants as the previous year.

Worse yet, when I turned the cow herd into that mess of tarweed, they wandered around bawling and swinging their heads, obviously unhappy, their faces covered with nasty, sticky tar and tarweed seeds. I watched as the cows lowered their heads, poked around a bit, then raised back to stare at me and beller piteously. It was horrible. After two days on what should have been a 9-day grazing pattern, I surrendered and moved the cows on.

I was defeated, and those paddocks were lost for the year. I lost the first early grazing when I delayed bringing in cows, as I tried to be a good manager. I lost the second grazing to the stinking, sticky tarweed. Perhaps there would be late-season grazing, but the vast majority of the biomass in those paddocks appeared to be tarweed, and it was hard to be optimistic. I was depressed and mad and ready to begin a war on tarweed.

Late that night I sat in my old lounge chair, silently plotting my revenge. I visualized huge propane burners dragged along behind articulated tractors, singeing the landscape…chisel plows…hundred-foot wide spray booms spewing death…new fences built to contain hordes of goats, creatures who could be starved into masticating the dreaded tarweed to death. VICTORY WILL BE MINE.

Cooler heads prevailed.

Eventually, I recalled the advice of Sun Tzu. In The Art of War the master notes that you should know your enemy prior to beginning the battle. And so, I began reading up on the tarweed family.

Next week I’ll share what I learned about tarweed and give you some tips for how to learn more about your own weeds and how to use what you learn to approach managing them in sync with nature.

Happy Grazing!

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