Weeds are a common, frustrating problem here in the UK. You want to keep your property looking pristine, and a strong weed killer is a no-brainer defence against a wide variety of invasive species.

There’s just one problem: weed killer typically doesn’t discriminate. The last thing you want is to cause inadvertent harm to other plants in your yard. So does weed killer kill trees? If so, how can weed killer kill trees so you can avoid inflicting damage?

You’ve come to the right place. The short answer is yes, herbicides can absolutely have a negative effect on trees. We’ll explain how below and offer more insights into the types of trees most at risk and the herbicides that do the most damage.

Most importantly, though, you’ll learn how to protect trees while eradicating those pesky weeds that have taken over. It’s as simple as finding the best weed killer safe for plants and trees and applying it carefully. There are other ways to control weeds without herbicide, too. 

If you want to set yourself up for success controlling any weeds, look no further than our weed killer at Jennychem. Whether you need a bramble weed killer or the best weedkiller for ivy, a dandelion killer for lawns, or anything in between, Weedex Super will get the job done!

What is Weed Killer (Herbicide)?

First things first - what is weed killer and how does weed killer work? These chemical solutions are specifically designed to control or completely eliminate unwanted plants.

There are so many different types, from glyphosate to acetic acid weed killer, which means they work in various ways. However, the common theme is they disrupt the biological processes of weeds to prevent them from growing, spreading, or reproducing.

These products are essential in agriculture, landscaping, and garden maintenance to keep lawns, gardens, and pathways free from invasive plants, which seem to have a knack for popping up annually no matter what you do.

Herbicides can be classified as either systemic or contact-based, and this distinction is key. Systemic weed killers are absorbed by the plant and travel through its vascular system all the way down to the roots, killing it from the inside out.

On the other hand, contact-based weedkillers torch any parts of the plant they touch for a faster but sometimes less complete kill. Repeated applications may be necessary for more resilient weed species.

There is another way you can characterise weed killers, though - either as selective or non-selective. The differences here are even more important for those wondering, does weed killer kill trees? 

A selective herbicide targets specific types of plants, such as broadleaf weeds, without harming surrounding grass or crops. In contrast, non-selective herbicides will work well against any vegetation. 

While this approach is great for clearing large areas completely, it can sometimes raise red flags. So, can weed killer kill trees if you’re not careful about how you apply it?

Does Weed Killer Kill Trees?

The short answer is yes, herbicides can certainly pose a problem for trees, as they do for any vegetation they come in contact with. But as you can imagine there are a lot of moving parts here. 

What type of herbicide is being used? What species is the tree and how well established is it? Did you spray on the tree’s bark or are you worried about residual compounds in the soil? Let’s get to the bottom of all this below. 

How Can Weed Killer Kill Trees?

Even if it doesn’t actually kill the tree, an herbicide can still slow growth, compromise foliage, or leave the tree more vulnerable to disease and environmental stressors. So how does weed killer kill trees? There are a few concerns with weed killer and trees:

• Root Absorption: Applying herbicides to the soil helps kill the weed’s root system, but those harmful chemicals can also leach into the ground and be taken up by a tree’s roots. This is especially problematic around trees with shallow root systems.
• Leaf Absorption: Wind can cause herbicides to drift onto leaves if sprayed nearby, bringing those toxic chemicals into the tree’s vascular system. This will disrupt nutrient and water transport just as it does in the weed itself.
• Direct Trunk Exposure: Some herbicides penetrate through wounds or bark if applied near tree bases or used in high concentrations.
• Soil Contamination: Persistent herbicides remain active in the soil for extended periods, providing longer control of weeds but also potentially affecting tree health long after application.

All of this is to say that no matter how you use herbicides near trees, there is going to be some level of risk. The type of tree in question dictates just how high that risk is.

What Types of Trees Are Most At-Risk?

Some trees are more resilient to herbicide damage than others. You might have nothing to worry about, or you may need to be more careful, depending on the tree itself:

• Shallow Root Systems: Maples, birches, and willows absorb soil-applied herbicides more easily since they have expansive, surface-level root systems.
• Thin Bark: Young trees or species with thin bark (think beech or cherry trees) can suffer damage if herbicides penetrate their weaker protective layers.
• Deciduous Trees in Active Growth: These trees are more likely to absorb chemicals through their leaves and stems during the growing season, so spray drift is a concern.
• Grafted Trees: Herbicides that harm the rootstock could affect the entire tree, leading to a slow but certain death over the course of time.

Take a moment to think about the specific types of trees in your landscape. Identify those that are at risk so you can take extra precautions when controlling weeds around them. You can be more liberal with weed killer for trees if you don’t have at-risk trees to worry about.

Types of Weed Killers Most Likely to Harm Trees

As we touched on earlier some herbicides are more concerning when it comes to damaging trees. The most common culprits are non-selective herbicides. These typically contain glyphosate and triclopyr, aggressive chemicals that kill any plant life.

Other weedkillers might contain imazapyr or picloram to offer extended control after the initial application. The residual compounds left in the soil can continue harming tree roots for months to come.

While you’d think broadleaf selective herbicides are safer for grass so they should be safe for trees, that’s not always the case. Formulations containing 2,4-D, dicamba, or MCPP can still harm trees if over-applied or if they drift onto foliage.

We’ll talk more about this later, but you’ll need to carefully read the label of any product you apply near trees to avoid causing more harm than good. 

Signs Your Trees Are Being Adversely Impacted by Weed Killer

The sooner you detect weed killer damage on your trees the swifter you can take action to limit the impact and provide care for the tree. Here are some of the telltale signs a tree isn’t doing so well after exposure to herbicide:

• Leaf Curling or Browning: Discoloured, wilted, or distorted leaves indicate herbicide absorption.
• Defoliation: Premature leaf drop or sparse foliage can suggest chemical stress.
• Stunted Growth: Trees struggling to develop new growth may be suffering from herbicide toxicity.
• Dieback of Branches: Wilting or dead branches in the upper canopy are a common symptom of systemic damage.
• Bark Damage or Lesions: Some herbicides cause cracking, splitting, or peeling bark, which is especially problematic as it exposes the tree to infections.

Noticing these symptoms early lets you take steps to help the tree recover. Mild cases, such as slight leaf curling from spray drift, should resolve on their own as the tree sheds its foliage and grows new leaves.

But severe exposure, such as is the case when herbicides make their way to the roots, is harder to recover from. There are still measures you can take to support recovery, but death is more likely.

Addressing Herbicide Damage on Your Trees

The obvious answer is to avoid using weed killer for trees, but it might be too late for prevention. If you suspect a tree has been harmed by herbicide exposure try these techniques:

• Flush the Soil: Water the area deeply to dilute herbicide concentration in the soil and reduce additional uptake that could make matters worse.
• Prune Affected Areas: Remove dead or damaged branches to encourage new, healthy growth. These branches won’t recover anyway, and they’re just stealing nutrients and light from other healthy branches.
• Improve Soil Health: Apply compost or mulch around the tree to support root function and provide your tree with all the nutrients it needs to recover fast.
• Limit Further Stress: This should go without saying but avoid additional herbicide use, excessive pruning, or drought conditions while the tree recovers.

Keep a close eye on the tree in the days, weeks, and seasons that follow to assess recovery. You might need to consult an arborist if symptoms persist and determine if there is more you can do, or if it makes sense to cut the tree down and plant a new one.

Choosing the Best Weed Killer Safe for Plants and Trees (Plus Tips on Keeping Your Trees Safe)

The simple solution is to avoid any and all weed killer for trees, as there is always going to be some level of risk. That being said, certain weed killers are safer for plants and trees than others. We’ll share some options and advice on using weed killer around trees safely.

Selective Weed Killers That Won’t Harm Trees

At this point you should realise that a selective herbicide is your best bet for protecting your trees from damage while effectively killing pesky weeds. The three most common ingredients to look for are:

• 2,4-D: Targets broadleaf weeds but is gentle on turfgrasses and tree roots when applied properly.
• Dicamba: Works well in combination with other herbicides to eliminate more stubborn weeds that have shown resilience to standalone solutions.
• MCPP (Mecoprop): Commonly used in lawn-safe weed killers to control broadleaf weeds without damaging grass or established trees.

Again, check the label and look for some sort of explicit messaging about the product being “tree safe.” When in doubt, ask the manufacturer or someone at the store.

Using Pre-Emergent Herbicides Safely

They say an ounce of prevention is worth a pound of cure, and that’s where pre-emergent herbicides come into play. These don’t let weeds sprout in the first place and are the best defence for long-term weed management.

Always choose tree-friendly formulas, such as corn gluten meal-based options, which are organic and safe for established landscapes.

Even still, they must be applied cautiously to avoid harming tree root growth or disrupting soil health as a whole. Avoid applying these near young trees or those with weak, underdeveloped root systems.

Follow timing recommendations carefully as knowing when to spray weed killer can make or break your results. Before the growing season is your best bet.

Avoiding Root Zones and Drip Lines

One of the most common mistakes we see UK gardeners and homeowners make is spraying weed killer too close to the tree’s root system.

But even spraying near a drip line, the area directly beneath the outermost branches, can pose a problem. This is where most feeder roots are concentrated and anything that makes its way into the soil there will be absorbed. Use spot treatments instead. 

Timing Applications for Minimal Risk

We touched on timing for pre-emergent herbicides, but it matters regardless of what you’re using. Poorly timing your application increases the risk of tree damage. 

Early morning or late afternoon is the best way to prevent excessive evaporation and spray drift. Similarly, avoid spraying on windy days as herbicide droplets can make their way onto nearby trees or any other desired vegetation.

Better yet, try to limit herbicide application just to when trees are dormant, which is typically late autumn to early spring. They aren’t absorbing nutrients at this point, so they are less likely to uptake harmful chemicals as well.

The only problem is that weeds tend to follow a similar dormancy schedule and may be less responsive to herbicides outside of their active growth season, too. Do your research into the specific weed species and time accordingly. 

Using Shields or Barriers to Prevent Spray Drift

If you’re still worried about weed killer drifting onto your trees, simply cover them up while you work. Physical barriers cardboard or plastic sheets block mist from making its way onto the tree.

Or, use a better garden sprayer for the job with a low-drift nozzle. Apply at low pressure to reduce fine mist formation, which is more likely to spread away from the target area. 

Alternative Application Methods for Spot Treatment

Speaking of garden sprayers, these aren’t the only way to apply weed killer. There are better methods for those who are worried about precise application around trees.

Foam or gel herbicides can be applied directly to weeds without affecting the surrounding soil. Similarly, wiping herbicide directly onto weed leaves with a sponge or wick eliminates overspray risk. 

These spot treatments are worth trying if trying to spray carefully is just not realistic. But, have you considered the possibility of avoiding herbicides altogether? 

Alternatives to Weed Killer Around Trees

Whether you want to learn how to get rid of ground elder naturally or some other pesky variety, there are plenty of other methods worth exploring. Protect your trees by trying these instead.

Manual Weed Removal Methods

We know manual labour may not be your idea of a fun way to spend an afternoon or a weekend, but it’s the safest way to completely remove weeds without chemical intervention. 

Simply pulling out young or shallow-rooted weeds by hand is the most effective approach, as it ensures complete removal of the rot system. You can use a weed puller for easier removal of tap-rooted weeds like dandelions and thistles.

Manual removal may not be practical in larger areas, so consider using a stirrup hoe or cultivator to cut weeds off at the soil surface while minimising root disturbance to trees

Mulching to Suppress Weeds

Mulching isn’t just a great option for how to kill weeds permanently, it also improves soil conditions for your trees! It blocks sunlight and creates a barrier so weeds can’t sprout or spread. Meanwhile, it retains moisture and regulates soil temperature. 

Apply a 5-10cm layer of mulch around the tree’s base to suppress weeds and reduce seed germination. As far as what to mulch with, we recommend bark chips, shredded leaves, or wood shavings since they decompose and enrich the soil.

Just be sure to keep mulch away from the trunk of the tree as this can contribute to moisture buildup and fungal growth, presenting a separate but equally concerning problem.

Using Boiling Water or Vinegar Spot Treatments

You might consider using a homemade weed killer recipe UK gardeners have relied on for centuries, be it rock salt for weeds, boiling water, or vinegar. These are compelling because they appear to be “non-chemical” solutions, but be clear - they can sometimes pose similar issues.

Pouring hot water directly onto weeds damages plant cells, causing them to wilt and die. It’s the best driveway weed killer and also works well around cracks or gravel areas near tree bases. Just know it may harm tree roots close to the soil surface as well.

Household vinegar (5% acetic acid) can be used as a mild natural herbicide, but this would be too light against stronger outbreaks. You’d need horticultural vinegar (20% acetic acid), which is closer to what Weedex Super at Jennychem is made of. Keep in mind that acetic acid - the main compound in vinegar - can be just as harmful to desired vegetation as weeds. It’s non-selective. 

Encouraging Grass and Ground Cover to Outcompete Weeds

A healthy lawn or ground cover can naturally suppress weeds by competing for resources like sunlight, nutrients, and water. It just makes your property look better, too!

Overseed your lawn in the spring to thicken grass coverage and take up the space weeds would otherwise grow in. You could even plant a low-maintenance ground cover like clover, creeping thyme, or sedum to serve as a natural weed barrier.

Whatever approach you take, maintain soil fertility by testing and adjusting pH levels to favour grass and discourage weed growth. When the soil, grass, and trees are in balance, weeds will have a much harder time establishing themselves.

Final Thoughts on Weed Killer for Trees

So, does weed killer kill trees? As we wrap things up, it’s clear this is a very valid concern for homeowners and property managers. You want to keep your yard weed-free, but not at the cost of harming your trees.

Understanding how herbicides work, choosing the right formula, and using proper application techniques can help protect your trees while keeping your landscape pristine.

Our blog has more resources on what kills nettles permanently, weed killer and dogs, and weedkiller for artificial grass if you’re interested. At this point, though, it’s time to get to work controlling weeds around trees using the insights we shared above. 

Ultimately, the best method depends on the level of weed infestation, the trees you’re worried about, and the time of year. Implement the right weed control solution for your property today!