ASPCA Guide to Pet-Safe Gardening

"Protecting your pet from potential hazards in your yard is just as critical."
While gardens and yards are lovely for relaxing, they can also prove dangerous for our animal companions.
Our experts recommend you watch out for the following:
Poisonous Plants When designing and planting your green space, it's a good idea to keep in mind that many popular outdoor plants—including sago palm, rhododendron and azalea—are toxic to cats and dogs. Sago palm and other members of the Cycad family as well as mushrooms can cause liver failure, while rhododendron, azalea, lily of the valley, oleander, rosebay, foxglove and kalanchoe all affect the heart. Please visit our full list—and pics!—of toxic and non-toxic plants for your garden. 
Fertilizer
Just like you, plants need food. But pet parents, take care—the fertilizer that keeps our plants healthy and green can wreak havoc on the digestive tracts of our furry friends. Ingesting large amounts of fertilizer can give your pet a good case of stomach upset and may result in life-threatening gastrointestinal obstruction. Be sure to follow instructions carefully and observe the appropriate waiting period before letting your pet run wild outside. 
Cocoa Mulch Many gardeners use cocoa bean shells—a by-product of chocolate production—in landscaping. Popular for its attractive odor and color, cocoa mulch also attracts dogs with its sweet smell, and like chocolate, it can pose problems for our canine companions. Depending on the amount involved, ingestion of cocoa mulch can cause a range of clinical signs, from vomiting, diarrhea and muscle tremors to elevated heart rate, hyperactivity and even seizures. Consider using a less-toxic alternative, such as shredded pine, cedar or hemlock bark, but always supervise curious canines in yards where mulch is spread.
Insecticides Like fertilizer, herbicides, insecticide baits, sprays and granules are often necessary to keep our gardens healthy, but their ingredients aren't meant for four-legged consumption. The most dangerous forms of pesticides include snail bait with metaldehyde, fly bait with methomyl, systemic insecticides with the ingredients disyston or disulfoton, mole or gopher bait with zinc phosphide and most forms of rat poisons. Always store pesticides in inaccessible areas—and read the manufacturer's label carefully for proper usage and storage.