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Can Canada thistle be a remedy for overgrazing?

This 'pioneer species' may help maintain the soil surface

Canada thistle isn’t a weed, it’s a plant that pops up to cover bare spots in overgrazed pastures.

Of all the different species of forages that grow in my pastures, my favourite plant is the Canada thistle. It actually comes from southeastern Europe originally, so I am not sure how we Canadians got credit for it, but either way I’m proud to call it my own. Canada thistle is what I refer to as a pioneer species, and it is very good at its job! When I think of pioneers, I think about folks like my grandfather who settled this land. They worked hard and survived through some very harsh conditions. They were tough, and they worked tirelessly in extreme weather conditions, broke the land, which in turn, made our lifestyles here today a lot easier. This is a very similar situation to what happens in our pastures; when conditions are harsh for our plant communities, sometimes “weeds” or pioneer species become an issue.

As always, when I look at dealing with any management decision on my property, I like to address the problem instead of attacking the symptoms. In this case, the symptom is that there are “weeds” in my pasture. If I resort to tillage or spray to deal with this symptom, they will continue to reappear year after year. This is only a short-term fix or a Band-Aid solution. However, if I deal with the problem of overgrazing, I will find a long-term solution. This would mean using some better grazing management and following the four grazing concepts.

What is a “weed?” It is really only a plant that we have not found a good use for. The only reason we call it a “weed” is that it competes against our desired crops. From nature’s point of view, most of our “weeds” have a job to do. If you are wondering why the quotation marks, I believe that there is no such thing as a “weed.” They are pioneer species. When the growing conditions are harsh, these pioneer species come in to heal the land; they act like a scab and cover the ground. I have mentioned before that the thatch layer on the soil surface acts like our skin to protect the internal processes and when this thatch is injured, we need a scab to protect it in order for the skin to heal.

Let me describe to you what these harsh conditions might be for a baby grass plant. Our soil might be lacking in moisture or short on nutrients; maybe the land has been cultivated or the pasture overgrazed. If the thatch layer (skin) is poor it will allow for too much run-off and excess evaporation. You will be continually losing soil moisture. All of these would make the conditions unfavourable for the survival of a young new grass plant.

Now let’s look at our good friend the Canada thistle. It has a very powerful tap root. If we are lacking moisture, it can find it by digging down six or eight feet. It is pretty easy to see that while it is looking for moisture, it is going to be finding a lot of nutrients that are not available to the grass plants with much smaller root systems. If the desirable plants are overgrazed, they will be much weaker and unable to compete with the pioneer species. A lot of pioneer species are unpalatable which again favours their survival.

Our pioneer species have all the advantages due to the harsh conditions and get to reproduce. This, my friends, is a good thing, all because now the plant dies and the plant material remains as residue for the following season. It falls to the ground and gives the ground some protection. This residue left behind will now reduce run-off and evaporation. As it decomposes it will release nutrients that were previously not available at the soil surface. Another benefit is that these big root systems will also decompose and leave a beautiful network of tunnels through your soil which will improve aeration and water percolation. With this scab protecting our soil, a baby grass plant might have a chance of survival the following year, as long as we don’t screw it all up by overgrazing or tillage.

I have a question for you. What happens when you rip off a scab? In this case it would be killing the pioneer species by tillage or spray. I’ll tell you, if you rip off a scab, you will bleed again and nature will have to start the healing process all over again. This is how “weed” problems persist. If we leave the “weeds” alone and stop the overgrazing, the land will heal.

Forget about the Band-Aid fixes that only address the symptoms. We need to allow this process to take place, which can take a few years to complete, but as the land begins to hold more moisture and recycle more nutrients, the desired species will simply outcompete the pioneer species.

Of course this also means we have to manage our grazing correctly. Short graze periods, longer rest periods, increase your stock density and improve your animal impact. As the soil heals, we no longer need the scab so the pioneer species will disappear. Don’t get me wrong, they are not gone, the seed bank is full. They are only dormant waiting for the next time the soil needs healing. I am simply trying to make the conditions favourable for the desired forage to outcompete the “weeds.”

I do, however, have a dilemma; I have been unable to find a seed producer who sells certified seed for Canada thistle. If you need to heal some land and you too are unable to find Canada thistle seed, I would recommend sweet clover. It is a biannual and needs harsh environmental conditions to cause it to germinate (like a drought). It has very similar characteristics to the Canada thistle, as it has a strong tap root, is unpalatable and can grow in harsh conditions. It also has an added bonus of nitrogen fixation. I do not add sweet clover to my seed mix as forage; it is added as a soil amendment. I want it out there to heal the land. If the cattle eat it, that’s fine but I want its root system and residue left behind. Even without seeding, your seed bank will most likely already include some very tough pioneer species that will assist you in healing the land. Let them do their job.

I must add, if your local “weed” authority has an issue with your new crop of pioneer species, do not give them my number. My recommendation is to mow them. Please take note; I did not say “hay them” as this removes the residue from the land. If you mow the area, the residue remains, helping to protect the soil surface. So next time you are looking at a field of pioneer species and cussing them, look to see if they are the symptom or the problem. You might save yourself years of frustration and a pile of cash if you take the time to address the problem, not the symptom. Remember, there is no such thing as a “weed.” Best wishes and God Bless!

Steve Kenyon runs Greener Pastures Ranching Ltd. in Busby, Alta.,, 780-307-6500, email or find them on Facebook.

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Steve Kenyon runs Greener Pastures Ranching Ltd. in Busby, Alta. You can email him at [email protected] or call 780-307-6500.

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