What Is Triclopyr Herbicide And How Does It Work?

There are many types of herbicides for plant control, and knowing which one to buy is difficult for many. Some of the herbicides used for vegetation control include Roundup, Garlon, Tordon and Grazon. In this article we’ll take a look at everything you need to know about Triclopyr and how to correctly use it.

Triclopyr is a synthetic, systemic herbicide used for controlling the growth of woody and broad leaf vegetation. Triclopyr is selective in nature. It works by mimicking an enzyme inside the plants called auxin, which is responsible for regulating plant growth. Triclopyr is not toxic to humans and it is effective all year round.

What Is Triclopyr?

Triclopyr was first registered in 1979 and it is a man-made chemical used for controlling both woody and broad leaf vegetation. Some of the most common uses of triclopyr include controlling the growth of broad leaf weeds such as nettles, docks and brambles. Triclopyr is a selective herbicide and is rarely effective against grass.

What Are Some of The Common Trade Names of Triclopyr?

Triclopyr is usually found as two compositions. One is called triethylamine salt (also known as triclopyr amine) and the second one is butoxy ethyl ester (also known as triclopyr ester).

While the former is sold as Garlon 3A and is often marketed as Turflon Amine or as Brush B Gone. The ester formulation on the other hand is sold as Garlon 3 and is often marketed as Turflon Ester. Some of the other trade names include Access, Crossbow, ET, Pathfiner II, Redeem, and Remedy. The previously listed products often combine triclopyr along with other herbicides such as picloram and 2,4-D to further increase the effectiveness and versatility of the herbicide.

Here you can read more about Garlon RTU, which also contains triclopyr.

Dow Agrosciences and Platte are some of the biggest manufacturers of Triclopyr products.

How Does Triclopyr Work?

Triclopyr is systemic in nature which means that it is absorbed by the leaves and stems of the tree. Once absorbed, triclopyr is transported throughout the plant using the trees’ vascular system.

Triclopyr works by mimicking an enzyme called auxin (indole acetic acid) which is already present within the plant. Auxin is responsible for controlling the growth of plants and trees. By mimicking auxin, triclopyr causes unregulated and uncontrolled growth within a plant which leads to its death.

It is believed that triclopyr causes the cells’ walls of a plant to acidify and loosen which leads to expansion without any control. At the same time, a low concentration of triclopyr stimulates RNA, DNA and protein synthesis. This results in uncontrolled cell division which in turn then leads to the destruction of the vascular tissue.

What Are the Uses of Triclopyr?

Triclopyr is used to control the growth of broadleaf herbs and woody species. It is recommended to use triclopyr along with methods such as foliar spray, cut stump treatment, or basal bark treatment.

Triclopyr is extremely effective on brooms which include Cytisus spp., Genista spp., Spartium spp.; gorses like Ulex spp.; fennel (Foenciulum bulgare). Triclopyr ester formulation is known to be effective on root or stem spouting species including buckthorns, ash, and black locusts.

Triclopyr is one of the most widely used herbicides because of it being easily accessible, effective and relatively safe to use. It also doesn’t impact grass which makes it perfect for home use.

Tips for Using Triclopyr

Depending on the brand and type of triclopyr you are using, the instructions differ slightly. Always read the label of your product very carefully before application or consult a professional.

It has been observed by some studies that the best time to use triclopyr is during mid-winter but this is largely based on the convenience aspect. During the winter season, triclopyr takes longer to decompose and dissipate which gives makes it more effective and gives it more time to act on the target plants.

The method of delivery also plays a major role in when to use the herbicide. For example, using foliar spray methodology, late spring or summer would be the best time. In my experience, the best time to use the herbicide is during the late spring to late summer, when the trees are going through active growth.

Randy Heirdom, Deputy Director for Stewardship of the Illinois Nature Preserve Commission (INPC) recommends the following tips for using Triclopyr:

  1. Use a mineral oil-based carrier for basal bark treatment.
  2. There shouldn’t be any snow, frost, dew, or water on the tree or plants.
  3. The most effective method of delivery is a combination of cut surface treatment and basal bark treatment. The chemical can both be sprayed and painted on the plant depending on the use.

What Are the Effects of Triclopyr On Humans?

Triclopyr is classified as a class D chemical and it is not known to have any carcinogenic effects on humans. While the salt and ester form of the compounds can cause permanent eye damage after coming in direct contact with the eyes, it is not very toxic.

Prolonged exposure of triclopyr to the skin can lead to allergic reactions. The compound has a low vapor pressure meaning that it is not that toxic through inhalation.

Through a study on rats, it was observed that triclopyr leaves the body primarily through urine within 24 hours. It is also interesting to note that the compound is not absorbed well through the skin, only about 2% of the dose is absorbed.

What Are the Safety Precautions While Handling Triclopyr?

While triclopyr is not known to be very toxic for humans, you should still be very careful while handling it.

Make sure you are wearing full sleeved thick clothes along with protective gloves, eyewear and a mask. Immediately wash the clothes once the job is done.

What Are the Effects of Triclopyr On the Environment?

There are a lot of slightly contradicting studies regarding the effects of triclopyr on animals, birds and aquatic life. It has been established that triclopyr is not toxic towards birds and long-term exposure to its acid form leads to added eggshell thickness.

All formulations of triclopyr are toxic to algae while only the ester form is moderately to highly toxic towards shellfish.

When it comes to fish, both the acid and the salt form are not toxic while the ester form is highly toxic. It should be noted that the ester form is known to bioaccumulate in fish, however, it is highly unlikely that fish will consume large quantities of triclopyr in any form, whether the triethylamine salt or butoxythyl ester.

What Is the Dissipation Mechanism of Triclopyr?

Triclopyr is majorly degraded through sunlight and microbial action within the soil. Both the formulations of the compound readily degrade under sunlight to form triclopyr acid which is also photodegradable. Sunlight is one of the major sources of dissipation.

The half-life of triclopyr acid under summer sun is only about 2 hours. While the half-life of the acid form in water is 12 hours.

Microbial degradation is the largest source of dissipation for triclopyr. The highest rate of degradation is observed when the soil has a high amount of organic content along with warm weather conditions. This is because the largest concentration of microbes within the soil is found under these conditions.

How Does Triclopyr Behave in the Environment?

There is a slight difference in the way Triclopyr interacts with the environment depending on the formulation you are using.

When triclopyr comes in contact with soil, both the formulations (triclopyr amine and triclopyr ester) degrade through photolysis, microbial metabolism and hydrolysis to form its parent compound called triclopyr acid. Once both the compounds have converted into the acid form, its movement within the environment is limited due to the compounds’ low adsorption potential.

The acid has a half-life of 30 days so it can take a couple of months for its effects to completely fade away.

The difference in its behaviour occurs when it comes in contact with water. While the salt formulation can dissipate within a couple of hours under the right condition, the ester formulation is not soluble in water. Thus the ester formulation will take much longer to degrade.

Both the formulations are converted to triclopyr acid form within plants and then transported throughout the plant’s vascular system. The chemical will be present within the plants until the plant’ tissues have fully decomposed.

What Are the Alternatives to Triclopyr?

Triclopyr is one of the widely used compounds for plant growth control along with Glyphosate. As it is a topic of its own, I wrote an article comparing both triclopyr and glyphosate in the linked article.


Triclopyr is a systemic, synthetic and selective herbicide which is ideal for controlling the growth of woody and broad leaf vegetation, but it is rarely effective on grass. It works by mimicking ‘auxin’ which is essential for controlling plant growth. It is classified as a class ‘D’ herbicide and is not considered toxic for humans.