How sweet it isn’t: Homeowners need to be aware that spreading cocoa-bean mulch in their gardens can be toxic to dogs.

“Dogs are attracted to the fertilizer’s sweet smell, but the mulch is too much for them to handle,” says Greg T. Rinckey, deputy chief for law enforcement of the Schenectady County SPCA in New York.

Cocoa-bean mulch, a byproduct of the chocolate-making industry, contains residual amounts of theobromine, the same type of cardiac muscle stimulant and diuretic found in chocolate and caffeine. It’s the same chemical that can make eating a chocolate bar toxic to dogs. Ingestion of large amounts, the SPCA says, can lead to hyperactivity, muscle tremors and possibly more serious neurological signs. Even amounts as small as 2 ounces can cause gastrointestinal upset.

“It is best to avoid contact with cocoa mulch at all,” Mr. Rinckey says. “Consider using a nontoxic alternative instead,” such as shredded hardwoods or compost.