I received this info and just thought I'd pass it along since it's gardening season. Be careful when choosing a mulch for your gardens in areas your dog(s) may have access to. Cocoa Mulch contains two key ingredients found in chocolate: theobromine and caffeine. Similar to eating chocolate, a dog that eats just a few ounces of cocoa mulch could start having stomach problems and it could get worse if it eats more. The chances of a dog actually eating mulch may be small, but dogs can eat some pretty crazy things. There is much more info here:
http://www.snopes.com/critters/crusader/cocoamulch.asp