What is Basal Bark Treatment & How Does It Work + Guide

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Basal Bark treatment is one of the most popular methods used for controlling invasive plant and tree species. There are a lot of details when it comes to the application of the technique and without the proper steps, there is a risk of failing to control the plant growth or damaging the nearby vegetation by accident.

Let’s take a look what is basal bark treatment and how to properly carry out the treatment process.

What is Basal Bark treatment?

Basal bark treatment is a method used for controlling plant and tree growth by spraying the bottom 3 feet of the tree’s trunk with a herbicide or herbicide mixture that is approved for bark treatment.

How Does the Tree Killing Process Work?

After spraying the herbicide on the trunk of the tree, it will be absorbed and transported to the roots and the leaves across the tree.

The chemicals in the herbicide cause a hormonal disbalance within the tree, which affects its regulatory functions such as protein synthesis, respiration, cell enlargement, and cell division capabilities. These functions are essential for any tree or plant to grow and survive, if these are affected then the tree will slowly die off.

This process will take at least a couple of weeks before you can slowly start to see the results. The first sign of the process working is going to be a stop in the growth of the tree, including any new leaves, flowers, fruits, and shoots. The foliage of the tree will slowly start withering away and turning brown. This will keep going on until there is no foliage cover, and all of the stems and branches dry out.

After basal bark treatment, depending on the size of the tree, it will take between 6-20 weeks before the tree dies completely.

When Is Basal Bark Treatment Used?

Basal Bark Treatment is primarily used for controlling the growth of small to medium-sized woody plants that are too tall for the foliar spray technique. It is the most suitable for areas where the tree density is low to moderate and the area can tolerate some standing dead plants.

The Basal bark treatment is most effective on trunks that are woody and thin, less than 6-7 inches in diameter to be specific.

It is recommended not to use this method on trees that have scaly or papery bark. Loose bark prevents chemicals to be absorbed as efficiently.

If you are trying to control trees with flaky or papery bark, scrape off the hanging bark pieces before applying the herbicide to the trunk

What Equipment Will You Need?

Other than the protective gear, which I will be covering in the latter part of this article, you will need a low-pressure sprayer or a backpack sprayer. The type of sprayer to choose depends on the number of trees you need to kill.

Because the herbicide will be mixed with an oil-based solvent, make sure the nozzle, gaskets, hoses, and seals of the sprayer are fitted with oil-resistant components. This will prevent damage to the sprayer and can extend the life of your equipment by a significant amount.

If you are just working on a couple of trees, you can use a small, chemical-proof pressure sprayer.

For projects where you need to be highly selective of the tree which needs to be targeted, there are some rope wick or foam roller hand tools that can be used. Something similar to this product (Rosco Handheld wick applicator) They are cheap and pretty effective if you have to remove only a couple of trees at a time.

Choosing the Right Herbicide

The herbicides suitable for Basal Bark treatment are systemic in nature. This means that the chemicals are absorbed by the plants’ tissue and carried throughout the plant. For trees, the herbicide should also be oil soluble.

Ideally, you should choose herbicides that contain Trycloper or Trycloper Ester as the main chemical or use Imazapyr-based herbicides. For example, Garlon 4 Ultra, Relegate, Forestry Garlon XRT, Aligare Trycloper are good choices, but not available in every state in the US.

One herbicide that can be used is this Triclopyr from Amazon. (Affiliate link) 

The Solvent Mixture and Carrier Oils

The herbicides designed for basal bark treatment usually need to be mixed with an oil-based solvent for effective results. The carrier to use can be kerosene, basal oil, or diesel. The ideal proportion for mixing should be 1 part herbicide and 4-part solvent, so about 20-25% concentration.

Some types of herbicides in the market can directly be used for this method without needing to mix with anything like ‘Pathfinder II’, but these types of herbicides are more expensive.

There are a lot of herbicide varieties in the market, make sure to carefully read the label before using them.

The Procedure

Once you have the herbicide solution, spray the bottom 3-4 feet of the trunk with this solution and let it dry out, repeat this process again for better absorption.

It is important to apply the solution when the trunk of the tree is dry. The oil-based chemical solution is hydrophobic, meaning it will not be absorbed as effectively.

The basal bark method should not be used on wet areas like swamps or sites that have a lot of water in the nearby area or if the soil is saturated with water. The oil-based solution will end up contaminating the water and floating on top of it for a long time.

What Is the Best Time for Using Basal Bark Treatment?

One of the many reasons why Basal Bark Treatment is so popular is because of its versatility. This method can be used effectively all year round, but the preferred time would be spring and summer.

Because of the chemical solutions nature, it is not recommended to use them during rainy seasons. With deciduous trees, using this method during the winter season will have a slower result due to its slower metabolism which leads to a slower vascular system of the tree.

What are The Follow Up Steps After Using The Method?

Once you start seeing the results of using Basal Bark Treatment, it is important to continue monitoring the area to ensure that the species don’t sprout back. Usually, once the trees are dead, there is a chance of regrowth after a few months or even after a couple of years. You will have to monitor the affected area every once in a while, to make sure that there is no regrowth.

Basal Bark Treatment can be repeated if needed, but you have to follow the annual limit of the herbicide as specified by the products label.

The annual limit is the maximum amount of chemicals and herbicides which can be used on soil per year without harming it. Different soils and areas have different annual limits

If the method is being used while the species is going through its seeding or fruiting period, any equipment present on site, including your protective gear, shoes, clothing should be cleaned before leaving. Cleaning the equipment will help prevent the spread of the species to other areas.

Personal Protective Equipment You Should Use While Performing Basal Bark Treatment

When you are dealing with herbicides that contain strong chemicals, you have to follow all the safety guidelines. This includes wearing proper protective gear like gloves, masks, boots, and a PPE suit. You can buy these gears from any nearby hardware store or order them straight from Amazon.


Basal bark treatment is a method used for controlling the growth of woody plants with a smaller diameter than 6-7 inches from chest height. The method is applied by spraying the bottom 3 feet of the plant’s trunk with herbicide mixed with oil-carrier like diesel, kerosene, or basal oil.  

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