Roundup is a herbicide that’s used to remove weeds, grasses, and other plants that we do not want.
It is non-selective, meaning that it is going to kill any and every plant that is sprayed with it, including trees.
So spraying roundup by trees can kill them, particularly young trees or seedlings.
So let’s start – While roundup can kill trees, mature and large trees rarely if ever, suffer any negative effects.
Mature trees especially can survive rounds of applications, because, for example, mature trees have thick and hard barks, making it difficult for herbicide to penetrate and cause damage.
Now, let’s start if and when roundup can kill trees.
How Does Roundup Work?
Before getting in to how round up could affect trees next to it, it is important to first know what the herbicide does.
As we have already mentioned in the beginning, the purpose of roundup is to kill unwanted plant life, specifically weeds and grasses.
In a great deal, it is an affordable way to manage weeds in the landscape world.
Roundup is typically applied by a spray mist, that will become uniformly covered on the leaves or foliage of the plant to be killed. It is also a Glyphosate-based herbicide of high-phosphate.
Once round-up is sprayed to a plant, it is absorbed through the leaves, it then travels down through the phloem to the roots.
Once it reaches the roots, roundup it quickly deteriorates into the soil.
At this point, it now interrupts the plant chemical that is responsible for growing-promoting amino acids.
So, the plant begins to yellow, wilt, and die.
The herbicide takes effect within 10 days of application
The mode of action means the best time to spray roundup on weeds and other unwanted plants is when the transport system of the plant is fast and efficient.
So, you are going to have to determine if the plant is annual or perennial to determine the best time to apply it.
Generally, roundup will stay in the soil for up to 6 years once it is absorbed in the soil.
If it accidentally gets absorbed or is sprayed on a nearby juvenile tree, the glyphosate will accumulate in the tree’s phloem.
Unlike weeds and grass identify, the chemical can take years to break down.
In the meantime: The tree will incur slow damage until it dies or recovers, depending on how severe the damage is.
Can Roundup Kill Trees?
In theory, yes, roundup kills any type of plant, including trees.
In practice, this is not an easy task for roundup to kill an adult tree.
The simple thing is, roundup will have little effect on an adult tree if it is sprayed too close to it.
Depending on how much you actually apply, an adult tree will not be affected by a direct or moderated amount of roundup sprayed around their canopy.
This is an example of the surface area to volume ratio and explains that a small to moderate doses of roundup would not significantly affect a whole tree.
In essence, there will not be enough chemical accumulation so that herbicide is a considerable factor in translocation and is absorbed in the roots. As I said before in the article, mature trees have a thick, hard, near-impenetrable bark.
This means that if roundup either accidentally or intentionally hits the bark of the tree, it cannot penetrate the bark to access the phloem and thus in no way impact the tree.
Can Roundup Kill juvenile trees?
When roundup has no, or at best, little impact on mature trees, young trees are a different story.
If Roundup gets sprayed too close to yearlings, superficial trees, or seedlings, it has the potential to kill them.
Young trees are very susceptible to roundup as their bark is not strong enough or mature enough to protect the tree from the effects of roundup.
Young tree bark has chlorophyll and readily absorbs and transfers the chemical.
This means that when roundup contacts a young tree, it will show visible effects.
These effects include:
- Bark splits
- Chlorosis/Yellowing
- Cupping
- Witches brooms
- Stunted growth
When barks splits, it makes it impossible for trees to maintain health since they now face the risk of pathogens, and increase the likelihood that the tree will catch a disease.
This is only evidence that the misapplication of roundup to non-target trees can inflict sub-lethal damage for years.
I use the term ‘non-target’ because, if not most often, roundup can be blown by the wind and flow with rainwater towards the tree, which is unintentional.
Can Roundup Kill Tree Suckers?
One of the common mistakes people make with roundup is to use it to kill tree suckers.
Since suckers are directly related to a tree’s vascular system, using roundup not only is going to result in a contamination problem, but it is going to quickly create damage.
Instead of spraying a tree sucker with glyphosate, pruning it is a better and safer option.
Remember – The ideal time to prune tree suckers is during the dormant season.
How To Ensure Young Trees Don’t Get Damaged If Round-Up Is Sprayed Too Close to Them
As we’ve discussed already, young trees are not immune to the effects of glyphosate.
So if you are spraying roundup close to a small tree, you have to take some protective measures that will ensure that the tree does not come into contact with the deadly chemical.
Here are some examples.
Shield the tree before spraying
When you are spraying roundup on a windy day, chances are high that the chemical will be blown to nearby plants.
So you want to make sure that you cover any nearby young trees with some appropriate material.
Some options are fleece, plastic, or even an empty plastic bottle if its a tiny seedling. Cardboards work pretty well, too.
Spray roundup when it is calm
You can also wait until it is calm before spraying the chemical on the plants you want to kill.
In this way, the wind can not redirect the herbicide to the plants you want to keep.
Although this method isn’t always foolproof, therefore you may still want to cover nearby young trees just to be sure.
Lower the spray tank pressure
Keeping the nozzle of the spray bottle at the lowest pressure reduces the size of the spray.
That way, the odds of it getting whisked away in the wind and landing on nearby juvenile trees is drastically lowered.
Apply roundup with a brush
If the weed and grass is extremely close to your juvenile trees, think about using a paintbrush to apply the roundup.
As long as this process takes, it is methodical if you are sufficiently deliberate – the herbicide will only come into contact with the plants you apply it to.
Hand-pluck weeds that are in the immediate periphery of young trees
If you wish to remove the weed that is spatially close to a juvenile tree or surface tree, the most safe way to go about it is to hand-pluck it.
Make sure that you wear the proper protective equipment so you don’t hurt yourself while doing this.
Avoid using roundup if the tree’s roots are too shallow
There are many products that are alternatives to roundup for killing weeds right close to a juvenile tree- particularly if the tree’s roots run on the surface of the soil.
If the tree’s roots can access roundup, then those roots can absorb roundup, and if at all they survive, they can also be damaged.
So, in this situation, it is best to keep it simple and avoid using roundup altogether!
What To Do If a Tree Has Been Damaged by Glyphosate
The effect of glyphosate will last for years on trees.
So, the tree does not die immediately, as weeds and grass do.
As long as the tree lives, keep caring for the tree, there might be a chance it may recover, and hopefully grow normally.
Be careful to protect it from other stress or damage.
Water it if it is too hot, prune it, keep it away from insects and diseases.
Also, it is important not to fertilize the tree while it is damaged.
Fertilization puts even more stress on the tree because it basically forces the tree to grow faster. It would be much better to wait until the tree is back to its full health to fertilize.
How Can Roundup Kill Mature Trees?
It is nearly impossible to kill a mature tree by spraying it with roundup.
However, if you are insistent on killing a tree using glyphosate, there is a way to do it.
The way you would do this would be as follows:
- Drill holes into the bark of the tree, close to the base and inject a significant amount of roundup into the holes.
- Make sure not to drill into the center of the tree – leave a small buffer.
- Then, put half an ounce of glyphosate into each hole, and wait for it to work. Just be sure to follow all manufacturer’s directions!
Usually, the tree will be dead in roughly six weeks!
For maximum effectiveness – Apply when the herbicide is during the active growth periods, between late spring and early summer.
Final Words
Roundup has the chance to kill trees if applied too near them.
However, when spraying roundup near a mature tree, the chances of it having any effect is very slim.
An established tree has enough depth and strength to entrap an excessive amount of glyphosate from penetrating its system.
Young trees, however, are not established enough to absorb glyphosate.
Thus, using this chemical too close to juvenile trees will cause damage, and possibly death.
Thus, when using roundup too close to juvenile trees, make sure to take some precautions!