Douglas Fir or Pseudotsuga Menziesii belong to the evergreen family of Pinaceae Conifers. They vary a lot in terms of their sizes, growing anywhere from 70 to 330 feet tall. Some of the older Douglas Firs shed their lower branches, because of this the foliage can start from as high as 100 feet. This species has also been used as Christmas trees since the 1920s. they are also considered to be invasive in some areas.
Let’s take a look at how to kill Douglas Firs and its root system.
How to Kill Douglas Fir Trees?
Some of the most popular methods of killing Pseudotsuga Menziesii are:
- Foliar Spray
- Cutting the tree down and treating the stump with Herbicides
- Gridling or ring barking
- Basal Bark treatment
- Injecting the tree with killing chemicals
- Cut surface treatment
Talking about tree-killing methods, I would refer back to my more detailed article discussing each of the methods in depth.
The best way to kill a small Douglas Fir tree
Some small Douglas Firs can only grow up to 25-30 feet tall. They are fast-growing varieties and because of their invasive nature, they should be killed as fast as possible.
The first option is to simply cut down the tree using a chainsaw or an ax and treat the stump with a herbicide like Tordon RTU, Roundup, etc. A herbicide is used to prevent any further growth from stump and roots. (Recommended products to use here)
If you don’t want to cut down the tree, there are a few other options you can choose from to kill a small Douglas Fir.
Foliar Spray Technique
The other method you can go for is the Foliar Spray method. This is only applicable if the Foliage of the tree is reachable by the sprayer.
For this method, you will need a backpack sprayer and a herbicide.
Make sure there is no wind during this as the herbicide will get carried away. The leaves of the tree have to be dry to maximize absorption.
- Use an effective herbicide like Roundup, Triclopyr, or Orhto, which you can find here. If you do not use the herbicide referred previously, It is also recommended that you add some type of a dye to the herbicide to mark the trees which have been treated. This will come in handy if you have to kill multiple trees.
- Spray the foliage of the Pseudotsuga Menziesii with the herbicide. For extra measure, apply multiple coatings after the previous one has dried out.
- The herbicide will be absorbed by the leaves and transported to the roots, killing the entire tree including its root system over time.
The third method for smaller trees is the Basal bark Treatment, keep in mind that you can only use this method if the diameter of the trunk is less than 6-7 inches in diameter.
Basal Bark Treatment
You will need a backpack sprayer for spraying the chemical, a strong herbicide, and an oil-based solvent.
Ideally, you should choose herbicides that contain Trycloper or Trycloper Ester as the main chemical. For example, Garlon 4 Ultra, Relegate, Forestry Garlon XRT, Aligare Trycloper are good choices, but not commercially available in every state.
Because of this, I would recommend using Triclopyr, which you can find on Amazon. (Affiliate link)
The solvent to mix the herbicide in would be diesel, basal oil, fuel oil, or kerosene.
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’. There are a lot of varieties in the market, so make sure to read the label before using them.
- Once you have the solution, spray the bottom 20 inches of the Pseudotsuga Menziesii tree with this solution, fully saturating the trunk, and let it dry out.
- Repeat this process again a few times for faster absorption.
- Make sure that the tree is not wet while performing this technique as the oil-based chemicals are hydrophobic, which means they will not be absorbed as effectively.
The best way to kill a large Douglas Fir tree
A large Pseudotsuga Menziesii can grow up to 300 feet tall. The roots of Douglas Firs can cause damage to nearby properties like water lines, foundations, concrete slabs, etc.
You can use two methods together to speed up the process- Girdling along with Cut Surface Treatment.
Ringbarking
Ringbarking would be the easiest method for killing a large Pseudotsuga Menziesii as it will stop the nutrient flow from the roots to the stems and the leaves. Without nutrients, the tree will die over time.
- You will need to either get a hatchet, or a chainsaw for this method.
- remove a ring of bark around the entire tree, about 4-8 inches wide. It is helpful if you penetrate the cambium layer of the tree as well.
- For extra measure, spray herbicide along the exposed bark. Tordon RTU would be the best option to kill the tree.
Make sure you take all of the safety precautions and read the manufacturer’s label before using the herbicide.
Cut Surface Treatment
- Use an axe or a chainsaw to make deep gashes into the trunk of the Pseudotsuga Menziesii around the entire circumference.
- Within half an hour of making these cuts, spray or inject a concentrated herbicide Tordon into the cuts.
- Once the herbicide has been absorbed, spray it a few more times over the next week to increase herbicides efficiency and absorption.
What’s the best time to kill Douglas Fir?
The best time to kill Pseudotsuga Menziesii would be before they produce their cones which is usually around Autumn but it can change depending on the area they are growing in. The tree will require the most amount of nutrients when they are about to produce cones. Killing Douglas Fir before this will speed up the killing process by cutting off this nutrient supply.
Things to consider before removing a tree on your own
Pseudotsuga Menziesii trees have an invasive nature and their root system can damage nearby property such as water lines, gas pipelines, foundations, etc. make sure to check for any damage while or after removing the tree.
Should you hire a professional tree removal service?
If the Pseudotsuga Menziesii is small, you can manage to get kill it by yourself. On the other hand, if the tree is big, it can get quite tricky if you need to cut it down.
From killing the tree to getting it cut down and transported, there are a lot of factors to consider, and hiring a professional will take care of most of these problems. especially if the tree has grown into mammoth sizes.
On top of this, the cost factor also plays an important role. Figuring out all of these separate logistical details can turn out to be costly.
I will publish an article on how much you can expect to pay for tree removal.
Frequently Asked Questions
Can you kill a Douglas Fir without cutting it down?
Yes, a small Douglas Fir can be killed using Foliar Spray or Basal Bark treatment. For the most efficiency, girdling along with cut surface treatment should be used when the tree is mature.
Can Pseudotsuga Menziesii be killed using fire?
Douglas Firs are actually one of the most fire-resistant trees growing in the wild. Even though they can be killed using fire when they are small, it will be really difficult. When it comes to killing mature trees with fires, it can lead to a lot of safety issues and is not recommended.
Will Foliar Spray be effective on Douglas Firs?
Yes, the foliar spray technique works on Douglas Fir, although it won’t be as effective as it is on trees that have broad leaves. Unlike Douglas Firs needle-like leaves, bigger leaves provide a larger surface area to absorb the chemicals.
Conclusion
A small Douglas Fir can be killed using the Foliar Spray technique and Basal Bark treatment. For larger trees, you can use Girdling and Cut Surface Treatment, or both in conjunction. Alternatively, you can also cut down the tree and treat the remaining stump with a herbicide to prevent sprouting.
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I am the guy behind Theyardable.com. I grew up on a homestead and I am here to share the knowledge I have and things I learn while living in the countryside.
