5 Best Herbicides for Thistles

Canada thistle (a.k.a. Cirsium arvense or just thistles) is probably one of the most invasive plants in the home garden and has a reputation for being difficult to get rid of. It is difficult to manage Canada thistle and takes a considerable amount of work to succeed, but when you have a field/lawn/garden that is clean of this irritating plant, the effort you put into managing Canada thistle will pay off.Canada thistle is an annual weed with strongly lobed, spear-like, soft green leaves, and these leaves have small barbs on them. The flower resembles a purple poof-ball that will be formed at the top of the plant in clusters if permitted to go to flower. The flower would turn white and fuzzy, just like a dandelion seed head, if the flowers were approved to go to seed.

Using sustainable approaches, organic herbicides, or artificial herbicides, you may get rid of most thistles. The following guide focuses on the best herbicides for thistles control available in the U.S. market. The major specs are included in the comparison table below. Also, please read the buyer’s guide to learn more about the chemical solutions for killing thistles.

Southern Ag CROSSBOW32 Weed & Brush Killer – the best for non-crop areas!

Most unwanted trees and brush are managed by Weed & Brush Killer by Southern Ag. It can be used near your home on rangeland, grass pastures, and other non-crop lands.

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If you’d like to use mild brush herbicides in the flower beds, it is very appropriate. Within a few days, you will destroy any of the broadleaf weeds along the fences and roadsides. Butoxy-ethyl is used as an active component in it.

PBI/Gordon 652400 Speed Zone Lawn Weed Killer – the best for the coverage area!

A fast-acting chemical will soon liberate your garden from weeds. Those speedy weed killers, though, quite sometimes end up killing the lawn.

Therefore, this Gordon 652400 weed killer is what you need if you are searching for the right spray for lawns that has no other impact on your turf.

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It just acts on the leaves of the weeds, ensuring that plants like grass are not affected. This SpeedZone product can easily leave you with a desirable lawn swept out of weeds. You will start seeing the improvements within a couple of hours.

Also, you can decide on this herbicide if you have a considerably wide lawn, as it will cover from 14,000 and 18,000 sq. ft. of land. Therefore, for covering a large-scale lawn, only one bottle of this substance is appropriate.

Therefore, if you’re searching for a herbicide that you can use on the most vigorous weeds on a large-scale yard, then seek no further than this Gordon’s herbicide.

RM18 Fast-Acting Weed & Grass Killer Herbicide– the best for quick performance!

Consider opting for a fast-acting chemical, such as the RM18 Herbicide, while destroying oxalis in flower beds. This killer of the oxalis flower bed will remove all weeds and grass from your flowerbed.

The manufacturer suggests wetting your goal weed leaf roots and leaves with RM18 to quickly destroy all the oxalis on touch.

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While being an excellent eradicator of oxalis, suggest cleaning your mouth vigorously with running water if RM18 interacts with your mouth.

RM18 will destroy oxalis in a yard or lawn, or around 3, 000 sq. ft., with 18% of the total ingredient as glyphosate. Just ft. In addition, as the glyphosate component present gives noticeable effects in the first 12 hours after applying, RM18 is a quick-acting herbicide.

Other important ingredients in RM18, such as salts and diquat dibromide, increase its effectiveness, rendering it an efficient herbicide in flower beds to destroy thistles, wild blackberry, kudzu, poison ivy, poison oak, and crabgrass.

Image 100099405 Kills Nutsedge Concentrate– the best for formula!

This post-emergent herbicide can be used on southern turf grass and chosen ornamentals. It can be extended during the year. Its proprietary one-of-a-kind formula operates by inhibiting the photosynthesis mechanism of the weeds, which effectively starves them to death.

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After a few hours of application, growth inhibition occurs, with yellowing taking place 1-2 weeks away. Within 3-5 weeks, the full effects are shown.

The hardest southern plants, including yellow and purple nutsedge, dollar vine, wild onion and annual bluegrass, can be killed with this Image herbicide. The substance can be easily used on most southern grasses as well.

Use this concentrated chemical formula to give your lawn the look without the weeds. For use in southern turf grass and chosen ornamentals, this herbicide is one of the best picks.

PBI/Gordon QT Trimec Lawn Weed Killer– the best for the cool season!

For any household, this weed killer offers the protection from a wide range of broadleaf weeds. It destroys lawn weeds that are hard to handle. It was built for cool seasonal grass applications.

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One of the most concentrated formulas in the market. You should blend it with water. Bear in mind that up 1 quart may treat 8000 sq. ft.

For DIY fans, this liquid could be a perfect choice. The budget-friendly alternative is for you if you are comfortable combining and spraying herbicides. As well as 250+ other lawn weeds, this product does a fine job of suppressing crabgrass.

The Buyer’s Guide

What thistle species can be treated with herbicides:

• Cirsium arvense a.k.a Creeping thistles;
• Cirsium vulgare is also known as Spear and Marsh thistles;
• Onopordum acanthium is known as Scotch thistle;
• Silybum is Milk thistles;

Active components

Glyphosate. On young thistle seedlings, glyphosate can have a positive impact, but it is not ideal for paddock conditions where a specific herbicide is much needed. This form of weed killer specifically attacks the weeds, but other plants that are near the weed typically do not destroy it. For flower beds and barriers that have thistle sprouts, this allows it a perfect option. If you want to deal with a plot without destroying the other plants, use this weed killer.

One of the country’s cheapest and most popular weed killers has a label that you’ve actually never heard before: 2,4-D. By having the cells of the undesirable plant develop out of reach this chemical may kill not only grasses, but also fruits and vegetables, may target both the roots and leaves of weeds. 

It is commonly used in the fields of soybean, maize, sugarcane, and wheat in cultivation, and it occurs in most items of “grass and feed” as well as in certain lawn treatments. The thing is, under today’s criteria, the herbicide that was once deemed clean and green might not be healthy anymore.

Application timing

The period from March to May is one of the best ones to apply Glyphosate, clopyralid, or Aminopyralid to control thistles. The perfect time to apply this is when the temperature range is between 65 and 85F on sunny days.

Because many herbicides are non-selective, everything they hit would be killed, so it is better not to use them on windy days. If you need to handle thistles where the plants you want are closer, you could be best off painting the weed killer on most thistles with a paintbrush.

What areas have to be treated?

Thistles are among the weeds that are mostly reviled but are readily identifiable. Lawns, grassland & paddocks can be overrun quickly. 

All of the key spots for thistle development are grassland fields, path edges and uncultivated soil. As a protection mechanism toward grazing herbivores, thistles have established their spiky leaves and may swamp a grazing paddock or lawn quickly-out-competing grass and limiting usable forage.

By reducing the numbers in a field, digging/ dragging out thistle weeds will function for new paddocks. Soft soils are needed to complete the treatment after rain, though, and there is also the possibility of leaving behind delicate root fragments to re-grow.

FAQ

Is there a specific time of year when you should apply herbicides for thistles?

Herbicides for thistles can be applied any time of year. However, it is important to note that they will be most effective when the plants are actively growing. This means that you should apply them in early spring or late summer/early fall.

Applying herbicides during these times will ensure that the plants are absorbing the chemicals and that they are being effective. If you apply them during periods of dormancy, the plants will not be able to absorb the herbicide and it will be less effective.

Which Roundup is best for thistles?

The best Roundup for thistles is the one that suits your needs the most. If you have a large area to cover, then you may want to consider a concentrate. However, if you only have a small area to treat, then a ready-to-use product would be more suitable.

There are many different types of herbicides on the market, so it’s important to do your research and choose the one that will work best for your specific situation. You should also take into account the time of year and the stage of growth of the thistles when deciding which herbicide to use.

How long does Roundup take to kill thistle?

Roundup is a very effective herbicide that will kill thistles quickly. However, to avoid harming other plants or animals, it is critical to follow the instructions on the Roundup label meticulously. Roundup usually takes about 24 hours to kill thistles.

If you have a thistle problem that is particularly difficult to control, you may want to consider using a stronger herbicide. Glyphosate-based herbicides are among the most effective for killing thistles. These products usually take about 48 hours to kill thistles.

Of course, no matter what type of herbicide you use, it is important to follow the directions on the label carefully in order to avoid harming other plants or animals.

How many ounces of Roundup will kill thistle?

The amount of Roundup needed to kill thistle depends on the size and age of the plant. For example, it takes about four ounces of Roundup to kill a one-year-old thistle that is six inches tall. To be safe, always follow the label directions when using any herbicide.

Roundup comes in both liquid and granular form. The liquid form is more concentrated and will work faster, but the granular form is easier to apply. If you choose to use the granular form, make sure you water it in well so that it can reach the roots of the plant.

Roundup can be applied either with a pump sprayer or a hose-end sprayer. If you are using a pump sprayer, you will need to mix the Roundup with water according to the label directions. If you are using a hose-end sprayer, you can simply attach the bottle of Roundup to your garden hose and spray it directly on the thistles.

What is the best product to kill Canadian thistle?

The best product to kill Canadian thistle is one that contains glyphosate as the active ingredient. Glyphosate is a herbicide that will kill any plant it comes in contact with, regardless of the species. However, Canadian thistles are very difficult to control and may require multiple applications of glyphosate before they are completely killed.

Roundup Ready-To-Use Weed & Grass Killer III is one glyphosate product that can be used to kill Canadian thistles. You can find it at most home improvement stores, and it comes in a convenient ready-to-use pump sprayer. Roundup products contain other ingredients in addition to glyphosate, so be sure to read the label carefully before purchasing any weed killer.

Another glyphosate product that can be used to control Canadian thistles is Ortho Ground Clear Super Concentrate. This product is a little more concentrated than Roundup and may require the use of personal protective equipment, such as gloves and a respirator, when applying. Ortho products can be found at most home improvement stores as well.

While glyphosate is the most effective herbicide for Canadian thistles, there are other products that contain different active ingredients that can also be used. Triclopyr is another non-selective herbicide that can be used to kill Canadian thistles. Products containing triclopyr include Scotts Turf Builder Weed & Feed and Miracle-Gro Shake ‘n Feed All Purpose Plant Food + Weed Preventer.

Video Tutorial: Gordon’s Trimec Lawn Weed Killer

Final thoughts

Thistles can and should be controlled with the help of powerful chemicals. Make sure to read all the recommendations before picking the herbicide for thistles online. Do not forget to leave your feedback about the use of each product applied.