How to Kill Thistle Weeds in Your Yard?

Do you struggle with thistle weeds constantly popping up in your yard? Why does it seem like every time you have it killed, it rears up its head again?  When trying to grow a beautiful lawn, many people in the northern and western parts of our country struggle with a pretty, purple-headed weed with wicked thorns called thistle.  Some people claim thistle is edible and rich in nutrients. Other folks claim thistle is good for reducing swelling.  But most people just consider thistle to be an invasive weed. So how do you kill thistle weeds in your yard?

These five methods are effective in getting rid of thistle weeds from your yard.

  • Kill Thistle by crowding it out.
  • Use mulch to cover up the weeds and kill them.
  • Kill Thistle by digging it up.
  • Kill Thistle by using organic methods.
  • Use chemicals to kill Thistle.

Thistle is hard to kill, but it can be done.  Let’s take a look at the steps to implement these methods.

5 Effective Ways to Get Rid of Thistle for Good

Whether you decide you want to go organic or chemical, you will find many remedies for killing thistle listed below.  Each will be described in detail so you can be successful in getting rid of thistle.

Kill Thistle by Crowding it Out

One great organic way to control thistle is to just simply to crowd it out.  You can use different dense grasses to accomplish this.

Before planting dense grasses, start with a clean lawn.

Step 1: Inspect your lawn closely.  Check for any thistle rosettes.

Step 2: Put on gardening gloves to protect yourself from little tiny thistle spikes.

Step 3: Grasp the entire thistle rosette at the ground and pull it up, getting as much of the root as you can.

Step 4:  Dispose of thistle only into a trash can.  Do not compost.

Step 5: Identify a dense grass for your yard.  Two good choices are creeping bentgrass and zoysia.  Both are tolerant of being mowed close to the ground which keeps the thistle crowded out.  Zoysia grows very slowly so it is easy to keep it low to the ground.

Step 6:  Put out seeds for bentgrass, or put in plugs for zoysia.

As you wait for the dense grasses to grow, keep your lawn mowed very close to the ground to crowd out the thistle.

Kill Thistle With Mulch or Rocks

 Putting down a good layer of mulch is the easiest way to get rid of thistle once and for all.  But it’s hard to do on a lawn.  You have to choose how much of your lawn you want to cover up, either temporarily or permanently.

Step 1:  Go to your lawn and garden store and buy thick plastic sheeting and several bags of river rocks, or several bags of pine mulch nuggets.

Step 2:  Lay the sheeting the ground over the thistle spot.

Step 3: Cover the sheeting with 2 inches of rock or mulch.

So if you have a big area where thistle keeps coming up, this a great place to use the mulch idea. It is also very effective at keeping thistle from coming back.

Kill Thistle by Digging it Up

If you are physically strong you can kill thistle by digging it out of the ground.   This method is very labor-intensive and will take a few years for all the plants to be killed.

Step 1: Soak the ground around the thistle plant until it is moist several inches down.

Step 2: Go to your hardware store and buy a potato fork.  This tool is also called a spading fork.

Step 3: Dig down into the earth around the thistle rosette that rests on the ground.

Step 4: Carefully loosen the earth all around the plant, to a depth of about 10 inches. Don’t use a shovel to get out the thistle roots, it will just slice through the roots and the thistle will return.

Step 5: Break up the soil around the plant very carefully with your fingers.

Step 6: Slowly pull out the plant while making sure all of the root comes with it.

Step 7: Look very carefully at what you pull out. You want to make sure you have one long root and several shorter roots that extend out to the sides of the main root.

Step 8: Put plant and roots into a trash can. Do not compost.

As you are doing these steps, treat the thistle very gently.  If you pull too hard, the roots will break off.  If even a tiny bit of root remains in the soil, it will send out shoots all over again.

Kill Thistle with Organic Methods

Fortunately, there are many organic ways to kill thistle. Not only can you put down mulch and dig it out as mentioned above, but you can also try the methods below.

Option 1: Insects

Step 1:  Go to Weedbusters Control, LLC, online, and order insects that make their nests in the thistle stem.  These insects are called Canada thistle stem weevils.

Step 2:  Insects are a very slow way to kill thistle.  In the meantime, go to your home and garden store and buy horticultural vinegar and a syringe.

Step 3: Snip the thistle plant off, as close to the ground as possible.

Step 4: Fill the syringe with horticultural vinegar.

Step 5: Put the syringe into the hole in the center of the thistle stem.

Step 6: Insert the syringe as far as possible into the stem and inject the vinegar.

Option2: The Boiling Water Method

Step 1:  Cut the plant stem right down to the soil.

Step 2: Pour boiling water into the stem.

Option 3: The Salt Method

Step 1:  Buy Epson salts at the drug store.

Step 2:  Cut off the thistle plant down at the soil level.

Step 3: Pour the salt onto the stem.  Be sure you completely cover the stem.

With vinegar and with salt, be aware that if it rains soon after your treatment, you will need to repeat your application and hope it stays dry a few days.

Kill Thistle with Chemicals

 If you have decided to go the chemical route, killing thistle is still a labor-intensive undertaking.  Many different kinds of chemicals can be used.

Option 1: Try glyphosate

Step 1:  Go to your lawn and garden center and buy a product with glyphosate in it.

Step 2:  Apply glyphosate to only the thistle.    Otherwise, it will also kill the grass around the thistle.

Option 2: Try clopyralid

Step 1:  Go to your lawn and garden center and buy clopyralid.

Step 2: Apply clopyralid only to the thistle. Otherwise, it will also kill the grass around the thistle.

Option 3: Try Weed and Feed

Step 1.  At your lawn and garden center look for packages of a product called weed and feed.

Step 2.  Apply to your lawn with a seed spreader.

Weed and seed products typically feed the grass while killing weeds.  Just like with all thistle killers, it will probably take several seasons of applications before the thistle is completely gone.

To sum up, you can see that there are several different effective ways to get rid of thistle weeds both initially and long-term.  There are two words to remember:  persistence and patience.

How to Prevent Thistle Weeds from Coming Back

Once you have done all the hard work of getting rid of your thistle weeds, you will want to keep them from coming back.  Below you will find some tips that should reduce the chances of thistle returning.

Kill the roots:  Thistle will not come back if you are careful to kill the roots.  When you dig it up, you have to be careful about the rhizomes.  The main root goes down vertically down into the ground and is generally easy to get out.  But the rhizomes grow out horizontally and are easy to miss. Unfortunately, when the rhizomes spread out to the sides, they produce a new plant every two inches.  Even though the main root is gone, the rhizomes are perfectly capable of producing new plants on their own.

Mow frequently:  A single full-grown thistle plant can produce thousands of seeds that can be easily carried all over your lawn.  The plant grows tall very quickly.  Once it makes the seed head at the top of the shoot, you have a problem. The seeds are light and fluffy and can catch the wind very easily. They can travel great distances.  If you keep your lawn mowed frequently, the plant won’t get a chance to shoot up and make a seed head.

Be vigilant: Go outside and walk your lawn in a grid pattern so you don’t miss a single inch. Look down as you walk, looking for small thistle plants that have just come up.  Even at a young age, thistle weed makes a distinctive-looking rosette-shaped plant which lies flat against the ground. It may even be visible a few yards away because it has killed the grass around it. This is an important time to dig it out. Remove the main root and be careful to get the rhizomes out of your lawn before it gets a chance to spread.

Frequently Asked Questions About Thistle Weeds in Your Yard

As you read about thistle weed and how to handle it, you may have some questions about the weed in general. The answers below may help you while you try to get rid of it and keep it away.

What is thistle? Thistle is a non-native plant that has become a problem in the United States. Twenty-two states have even declared thistle as a noxious weed.  You can recognize thistle plants by their spiny leaves and stems.  If you’ve ever tried to pull up a thistle, you won’t forget the spines sticking in your hands.

Are there any organic methods to kill thistle? Yes, there are organic ways to kill thistle.  Most importantly, keep your lawn mowed to the proper height. This encourages a thick lawn that will push out the thistle before it gets a chance to take hold.  It also encourages your grass to make a deep root system which also crowds out thistle weeds.

How do chemical herbicides kill thistle weeds? Chemical herbicides are absorbed by the plant.  Some herbicides are made to kill just thistle and broadleaf weeds, while other herbicides kill everything they touch, including grass in your lawn. Some herbicides kill the thistle by stopping cell growth within the plant.  Other herbicides keep the thistle from processing proteins.

Will herbicides harm my lawn if I use them on thistle weeds? Yes, depending on which herbicide you use.  If you use anything with glyphosate in it, that is a non-selective herbicide that will kill everything that comes in contact with the spray, regardless of what that plant is.  Be careful to read the label when you choose an herbicide.  You want one that is selective for a broadleaf plant like thistle.

What is a thistle “rosette”? Many thistle control solutions tell you to treat the “rosette” of the plant.  The rosette is what you find growing close to the ground, not the stem that shoots up from the middle.  It is easy to recognize because of its circular shape. It grows flat to the ground and crowds out the rest of the nearby grass making it easy to recognize in an otherwise healthy lawn.

Are there any tips for avoiding thistle weeds in the first place? It’s very important to keep your lawn trimmed to the proper height to keep from getting thistle.  In wet weather keep your lawn shorter because thistle likes a soggy lawn. Thistle also likes barren spots that have no vegetation on them at all.

Wrap Up

As you can see, thistle weeds are a big problem for some homeowners. About now, you are probably thinking you will just plow up your whole yard and reseed your grass to get rid of the dreaded thistle.  Unfortunately, it won’t be killed this way. The rhizomes will still be in the soil; the seeds will still be carried in on the wind. Stick to the methods listed in this article.  With time and repeated applications, it is possible to kill thistle in your yard for good.

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