Miracle-Gro plant food is not designed for pet consumption, but according to the company, "No animals have had any adverse reaction to accidentally consuming All Purpose Plant Food."
Miracle-Gro is considered practically nontoxic. The Material Safety Data Sheet for Miracle-Gro Water Soluble All Purpose Plant Food 24-8-16 notes that the product can cause irritation of the gastrointestinal tract or respiratory tract. Eye and skin irritation are possible, but not expected.
Miracle-Gro contains no pesticides or herbicides. The product is made with food-grade ingredients.
To prevent accidental ingestion, store Miracle-Gro out of the reach of pets, and restrict pets from the area while you are using or mixing the product. The Scotts Company, makers of Miracle-Gro, recommends that owners monitor their pets for symptoms such as vomiting or diarrhea if accidental ingestion is suspected. Contact your veterinarian immediately if your pet consumes the product.