Is Your Garden a Minefield? The Truth About Mulch and Dogs - The Practical Planter (2024)

Mulch is one of the most important elements of landscape design. It not only beautifies your outdoor space but also suppresses weed, enriches soil, and retains moisture.

But while some types of mulch are safe for dogs, others can be dangerous or even deadly.

To avoid an untimely trip to the vet, this article covers everything you need to know about using mulch around dogs, including reasons behind their mulch-eating behavior and what to avoid.

Can Dogs Eat Mulch?

Dogs shouldn’t, and mustn’t, eat mulch.

Mulch can easily get lodged in a dog’s throat or gastrointestinal tract, leading to choking or stomach obstructions.

Even smaller pieces of mulch can cause problems, as they, too, can lead to blockages or perforations in the digestive system, especially when consumed in large quantities.

Such blockages can be life-threatening and more often than not require medical intervention.

There’s also the fact that certain types of mulch can be deadly to dogs. One such mulch is cocoa bean mulch, which contains copious amounts of caffeine and theobromine.

Caffeine and theobromine can be deadly to dogs, as reported by the Animal Poison Control Center.

Dogs that swallow cocoa bean mulch may experience vomiting, diarrhea, and rapid heart rate, as well as tremors and seizures.

Why Do Dogs Eat Mulch?

Dogs eat mulch for the same reason they eat anything else: the smell, texture, or taste.

Some eat mulch out of boredom or curiosity, while others, especially puppies, chew on mulch to explore their environment and relieve the discomfort of teething.

If you make your own mulch, chances are you’ve mixed in some leftover food. Dogs may be attracted to that smell and may be tempted to ingest the food residues it contains.

Sometimes, dogs seek out non-food items like wood, rocks, plastic, or mulch because of a condition known as Pica.

Pica can be the result of parasites, illness, or a nutritional deficiency, but it’s most common in dogs with mental health conditions such as depression, stress, anxiety, or extreme hunger.

Thankfully, Pica is curable. Treatment involves addressing any medical issues or nutritional deficiencies, managing anxiety or stress, and providing appropriate outlets for chewing.

Another condition that can be responsible for a dog’s obsessive behavior towards mulch is dog anemia.

Dogs with anemia—a condition characterized by a deficiency of red blood cells—may exhibit unusual cravings like mulch to compensate for the lack of iron in their bodies.

Is Mulch Toxic to Dogs?

Wood-based mulch chips made from pine bark, cypress, and cedar aren’t inherently toxic to dogs.

But cocoa mulch, which is made from cocoa bean shells, is.

Ingesting as little as 20 milligrams per kilogram (mg/kg) can result in mild chocolate toxicosis in dogs, leading to vomiting, bloating, and diarrhea.

Doses of 40 mg/kg and above can result in muscle tremors, seizures, hyperthermia, and, in severe cases, death.

Additionally, some manufacturers treat mulch with pesticides or chemicals to prevent weed growth, deter pests, or enhance its appearance.

Such mulches are toxic to dogs because they contain preservatives like chromium, glyphosate, and heavy metals, which can cause stomach irritation, vomiting, and organ damage in dogs.

What Mulch Is Bad for Dogs?

Mulch that are considered harmful to dogs include:

1 – Cocoa Mulch

Cocoa mulch is made from the leftover hulls or shells of cocoa beans.

It’s popular for its color and sweet smell, as well as its ability to retain moisture in garden beds and organically reduce weeds, eliminating the need for herbicides.

Unfortunately, cocoa mulch contains the same type of toxic compound found in chocolate: theobromine.

This compound is dangerous for dogs because they metabolize it more slowly than we do, causing it to build up to a level that’s toxic to their system.

Ingesting cocoa mulch can lead to chocolate toxicity, which can be fatal for dogs.

2 – Treated Wood Mulch

Treated wood mulch contains preservatives and herbicides that aid in weed suppression and pest prevention.

It’s treated with various chemicals such as Chromated Copper Arsenate (CCA) and Alkaline Copper Quaternary (ACQ), which contains chemicals such as arsenic, copper, and other heavy metals.

Ingestion of these chemicals can lead to symptoms of poisoning, ranging from gastrointestinal upset to more severe neurological effects, depending on the amount ingested.

3 – Pine Needle Mulch

Pine needle mulch, also known as pine needle straw mulch, is a natural soil enhancer that reduces weeds, insulates plants, and keeps the ground moist.

It’s beneficial for plants that require acidic soil because pine needles have a naturally acidic pH level.

Regrettably, pine needle mulch isn’t safe for dogs because it can cause internal injuries to a dog’s stomach.

Pine needles are long, slender, and pointed, so they can pierce the delicate tissues lining the mouth and esophagus.

This can lead to a range of issues such as inflammation, irritation, punctures, or blockages within the digestive system.

4 – Rubber Mulch

Rubber mulch lacks a natural scent, so it’s less likely to be chewed on by dogs.

Still, some dogs may show interest in rubber mulch out of curiosity, boredom, or lack of toys to chew on.

Rubber mulch contains heavy metals like phthalates, PAHs, and BPAs, which are not only toxic if ingested but can also cause gastrointestinal obstructions because they don’t break down.

What Mulch Is Safe for Dogs?

Just because you have dogs doesn’t mean you have to end your gardening journey. There are various mulches that are considered safe around dogs, including the types of mulches below.

But remember: regardless of how safe the mulch is, it’s still important to supervise your dogs while outside to prevent them from ingesting excessive amounts.

1 – Stone and Rock Mulch

Stone and rock mulch are considered safe options to use around dogs, as dogs generally aren’t prone to eating stones and rocks unless they’re afflicted with Pica.

They also don’t decompose like organic mulches, so they rarely pose a risk of toxicity or ingestion to dogs.

2 – Bark Mulch

Dogwood, crabapple, Douglas fir, and other tree barks aren’t harmful to dogs because they don’t contain toxic substances that could pose a risk to their health.

Tree barks are primarily composed of natural organic materials, which are less likely to cause stomach upset or obstruction if eaten compared to chemically treated and synthetic mulches.

3 – Untreated Wood Mulch

Untreated wood mulch made from shredded cypress, hemlock, or cedar are safe for dogs because, like bark mulch, they’re free from chemicals and toxins that can harm dogs.

Just make sure to periodically check these mulches for any signs of fungi, mold, and pests, as they’re more susceptible to those compared to chemically treated mulch.

What Can I Spray on Mulch To Keep Dogs Out?

To discourage a dog from digging, rolling, and eating mulch, use these solutions:

1 – Citrus

According to a 2020 study on canine smell preferences, dogs tend to display aversion or avoidance behaviors towards citrus fruits like lemons, limes, and oranges.

Therefore, spraying citrus-scented solutions on mulch may help deter dogs from approaching or interacting with it.

You can use commercial citrus repellents or make a homemade citrus spray by mixing lemon juice or another citrus extract with water.

Spray the solution on top and in the mulch.

2 – Cayenne Pepper

Cayenne pepper is another common ingredient used to deter dogs from mulch beds.

The spicy and pungent scent of cayenne pepper can be unpleasant for dogs, causing them to avoid the areas treated with it.

To use cayenne pepper as a detergent, mix one part cayenne pepper to 10 parts water and spray it in and on top of the mulch.

Don’t sprinkle cayenne pepper directly because it can irritate a dog’s nose, eyes, and throat if he accidentally gets in touch with it.

3 – Vinegar

Vinegar repels dogs in much the same way as citrus: it has a strong scent that dogs find unpleasant.

Mix one part vinegar to five parts water and spray the solution on the mulch.

This solution can double as a pest repellent, as many insects and bugs also hate the smell.

Be sure to reapply the solution regularly to maintain its effectiveness.

Final Thoughts

Not all mulch is safe for dogs.

Cocoa mulch, treated wood mulch, pine needle mulch, and rubber mulch are considered hazardous for dogs if ingested.

Cocoa mulch contains theobromine and caffeine, while treated wood and rubber mulch has chemicals like copper, arsenate, and creosote, all of which are highly toxic to dogs.

Pine needle mulch doesn’t contain chemicals but can injure a dog’s mouth, throat, and stomach because of its sharp edges.