The lone voice of horticultural reason

“Wait a minute, maybe dogs CAN be harmed by eating cocoa bean hull mulch”

 I finally write something about gardening and dogs, and sure enough, I wind up in the doghouse. A few updates back, I wrote a piece dispelling the “myth” that dogs can be harmed by lapping up cocoa bean hulls, a popular product used for mulching around annuals and perennials.

I didn’t check it out very thoroughly, mind you, the White Stripes were in town and I was running late for the concert. So I knocked it out after observing the dog activity around my gardens during fifteen years of cocoa bean mulch use, and after asking a few industry people if they had ever heard of problems. They hadn’t. And I had never heard/read/discovered anything suggesting that the mulch was a problem for dogs, so I finally published it as a myth because a few people had e-mailed me wondering if I had ever heard of cocoa bean mulch harming dogs.

BAD DOG. A few weeks ago, I received the following e-mail from a reader (edited for length), and I’m going with her take on the subject. This is what I love about hosting this site: You readers are my greatest resource. Even when you so clearly nail me to a wall …

Dear Don:

I concur wholeheartedly with most of your ideas and philosophies, however, I must challenge you on this one, the myth that cocoa bean mulch is not harmful to dogs. 

First of all, maybe your dog might not eat cocoa bean hulls, but there are a lot of dogs that do eat mulch, sticks and all sorts of stuff that other dogs would find repulsive. I was in business for over 10 years doing landscape design and installation and continue working in the industry. During the first 5 years I was self-employed, I specialized in landscaping for dog owners.

One of the first clients we had was Dr. Michael Murphy, a veterinary toxicologist at the University of Minnesota who wrote the book, “A Field Guide to Common Animal Poisons.” He deals day in and day out with animals that have ingested, inhaled, or somehow gotten into various substances.  The ingredient that is toxic to dogs in chocolate is theobromin. It is the most concentrated in the cocoa bean hulls (14-30 mg/gram of hulls), than in unsweetened baking chocolate (390 mg/oz) and dark chocolate, and least of all in milk chocolate (44 mg/oz). 

A median lethal dose for dogs is 250-50 mg/kg (0.67-1.33 oz of baking chocolate/kg of body weight of dog). However, there have been reported deaths after ingestion of as little as 140 mg/kg of weight of dog. Theobromin is rapidly absorbed from the GI tract and can cause vomiting, diarrhea, hyperactivity, cardiac arrhythmias, tremors, seizures, coma and death in less than 24 hours depending on the quantity ingested.

Because you are reputable and considered a professional, I am sure people believe what you write. It seems in most cases, from what I have read of your website, you site references to back up statements you make. However, you clearly did not do so in this case. 

Because I am a dog lover and dog owner, I believe it is important that people know the truth about things that can potentially harm or kill their dogs, especially deaths that could be easily prevented.  With the popularity (I believe unfounded) of cocoa bean hull mulch, I believe it is imperative that people who own dogs be informed that this mulch can be potentially harmful and even potentially toxic to their pet. 

Thank you Lynette, the Myth in question has been banished from my site, and if I ever find the guy who wrote it, he’s fired.

Don Engebretson
The Renegade Gardener