This mulch, sold by nearly every mulch retailer and used by many landscape companies, is made from cocoa bean shells - a by-product of chocolate production. It looks attractive and smells nice to humans and decomposes into organic matter. Not surprisingly, dogs find it attractive too. Consumption of small amounts of this mulch can cause your dog digestive upset and vomiting. Consumption of large amounts can result in tachycardia, muscle tremors, seizures and even death.
If you suspect your dog has ingested cocoa mulch, get him to the vet IMMEDIATELY!
The bottom line: next Spring, read the labels on your landscape products carefully!!!