The dangers of cocoa mulch

Mulch looks great in the garden. It’s attractive, protects your plants and makes life easier for you. But make sure you don’t buy cocoa mulch – it can be toxic to dogs.

Melissa has a young Lab pup. She adopted him after her former dog, a collie named Tabitha, died a sudden and tragic death. Melissa had purchased some cocoa mulch from her local garden center to put around the plants in her garden. “I just wanted to cut down on all the weeding and watering,” she says. Attracted by the mulch’s sweet smell, Tabitha helped herself to some mouthfuls. Early next morning, she had a seizure and died.

Most of us know chocolate is toxic to dogs. It contains a chemical called theobromine, a xanthine compound similar to caffeine that can be lethal to dogs. Humans have the ability to safely metabolize theobromine in their bodies, but dogs do not. Dark unsweetened chocolate contains up to ten times more theobromine than milk chocolate, but even the latter is harmful to dogs if ingested in large quantities.

Cocoa mulch is made from the shells of cocoa beans, and is a by-product of chocolate production. People like it because it has an attractive and natural color, a fragrant smell, and breaks down into an organic fertilizer. While cocoa mulch doesn’t contain as much theobromine as unprocessed cocoa beans – 0.19% to 2.98% versus 1% to 4%, according to the ASPCA Animal Poison Control Center – if enough of the mulch is ingested, it can have serious repercussions.

Theobromine affects the nervous and cardiovascular systems and can manifest in a variety of symptoms. The Animal Poison Control Center conducted a study of dogs that accidentally ingested cocoa mulch. Vomiting was reported in 50% of cases, tremors occurred in 33% and 15% of the dogs developed tachycardia, a rapid heart rate. No clinical signs were seen in a third of the dogs, likely because they ate only small amounts of the mulch. Other symptoms of theobromine toxicity include restlessness, diarrhea and, as in Tabitha’s case, even seizures and death.

The Merck Veterinary Manual states that the median lethal dose of theobromine is 100 mg to 200 mg per kilogram of a dog’s body weight, but adds that serious symptoms and death can occur at much lower doses, and that individual dogs have varying sensitivities to the chemical. “In general,” the manual continues, “mild signs (vomiting, diarrhea, polydipsia) may be seen in dogs ingesting 20 mg/kg, cardiotoxic effects may be seen at 40 to 50 mg/kg, and seizures may occur at doses larger than 60 mg/kg.”

Even if your dog isn’t an indiscriminate eater, it’s best to err on the side of caution and avoid using cocoa mulch in your landscaping. There are lots of alternatives to choose from, including mulches made from the wood or bark of cedar, pine or cypress, as well as straw, pine needles, grass clippings, stones, compost, shredded leaves or landscape fabric.

Needless to say, Melissa got rid of the cocoa mulch in her garden before adopting her new canine companion. She now uses redwood chips. “They look nice and neat, they keep the weeds down and the soil moist – and I don’t have to worry about my puppy being poisoned.”

What about cats?

We most often hear about chocolate toxicity in relation to dogs, but theobromine can also be harmful to cats. Like dogs, cats lack the ability to metabolize theobromine. But because cats aren’t as prone as dogs to eating non-food items, they aren’t as drawn to cocoa mulch and are therefore less likely to ingest it. Nevertheless, if you have cats that go outdoors, it’s a good idea not to use cocoa mulch in your garden.