Thought this may be of some interest.

by Sandra Mason

July 10, 2005

I'm a big believer in mulch. I don't know how I survived without long underwear, flannel sheets and mulch. However, as a University of Illinois Extension educator I have found that even a good thing can sometimes be a bad thing. People mulch plants too heavily (more that four inches) or they bury the trunk or stem.

The best mulch is one that is a by-product of some of our other landscape activities such as wood chips, compost, or grass clippings. One mulch, cocoa hulls, is a by-product of the chocolate industry.

As a bonus you get a chocolate smell when you put them in the garden. Some people tell me they also like the finer chips and more refined look of cocoa hulls.

Like other mulches the cocoa hulls help to prevent weed seed germination, moderate soil temperatures and help to conserve moisture. However, something I had never considered was that dogs might be attracted to the sweet smell of the cocoa mulch. Ok so what? So the dog likes to roll and dig in the cocoa mulch. If you are a dog owner, hopefully you know not to feed your dog chocolate since it can be poisonous to them. However, research has shown that cocoa mulch, which contains some of the same toxins as in chocolate, may be ingested as dogs dig through it.

Michelle Wiesbrook and Sharon Gwaltney-Brant reported in a recent University of Illinois Extension Home, Yard and Garden Pest newsletter that chocolate contains two compounds toxic to dogs. They are methylxanthines, specifically theobromine and caffeine.

So how much is too much for a pooch? As Wiesbrook and Gwaltney-Brant reported, the amount of methylxanthines in cocoa hulls is substantial at 255 mg/oz. And that's just the theobromine; no data was available for caffeine. In comparison, milk chocolate has only 64 mg/oz of methylxanthines, and less than 1 oz of milk chocolate/lb (2 oz/kg) is potentially lethal to dogs. So 65 oz (4 lb) of milk chocolate would be potentially lethal for a 65-lb dog. But, if she were to eat cocoa-hull mulch, it would only take about 2.25 oz to produce mild signs and 12 oz to be potentially lethal. Of course, these amounts would be much less for a smaller dog.

Some manufacturers do include a warning statement on the bag. If you have an older dog that isn't all that inquisitive, cocoa mulch may not be a problem, but if you have a young dog that tends to dig and chew, you may want to consider different mulch.

For more information, call your local veterinarian or animal poison control center. You can reach a link to the center by clicking on http://www.aspca.org. Also at this site is an article on chocolate intoxication that gives detailed information on clinical signs and treatment, as well as an example for calculating the methylxanthine dosage. At the above Web address, you'll also find information on protecting your pet from pesticides and fertilizers, as well as a list of plants that are toxic to pets. Thanks to Wiesbrook and GwaltneyBrant for alerting us to this potential problem.

Sandra Mason is a unit-based horticulture educator with University of Illinois Extension. She provides leadership and expertise in horticulture and environmental programs in Champaign County. Mason has a B.S. (with honors) in horticulture and a M.S. degree in agricultural education from the University of Illinois at Urbana-Champaign. She held a wide variety horticultural positions before joining Extension.