Palm fronds
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While sago palms (Cycas revoluta) might look innocuous and inviting, the hardy plants are highly poisonous to both human beings and pets. Cycads have several uses, from in containers in living rooms to shrub borders outdoors. Sago palms grow in U.S. Department of Agriculture plant hardiness zones 9 through 10.

Toxic to Human Beings

Sago palms are spiky plants that are toxic when eaten. All parts of the plant are toxic, including the thorns. The seeds, rather than the thorns, are the most dangerous parts. The seeds have the largest amounts of cycasin, a type of glucoside. Although all parts of sago palms are off limits, the seeds are the biggest risk factor, so stay far away from them. Cycasin can irritate your digestive system. Substantial levels of it can lead to liver failure. If the thorn of a sago palm tree punctures your skin, get medical help, just to be on the safe side.

Toxic to Pets, Too

Sago palms aren't just poisonous to people, but also to cats and dogs. Dogs especially seem to enjoy the taste of the plants. If you have sago palms in or around your home, make sure your pets can't get close to them. Pets that get their mouths on sago palms, thorns or otherwise, often experience symptoms like depression, weakness, vomiting, runny stools, appetite loss, bruises, exhaustion, severe stomachaches, unusual thirst and bloody fecal matter. If you notice any of these symptoms in your pet, get him to the vet immediately. Liver failure is always a possibility in cases of sago palm poisoning.

Immediate Medical Attention

If you ate part of a sago palm and have any unusual symptoms, seek immediate medical attention. Go to a doctor even if you don't have symptoms. Toxicity isn't always immediately apparent.

Know the Other Names

Never make assumptions about the safety of plants. Also never assume a plant only goes by one name. Sago palms are often called cardboard palms, fern palms and coontie palms. If you hear any of those names, stay far away from the plants. Keep your children and pets away from them, too.

Pay Attention to Your Surroundings

Sago palms are fixtures in rock gardens, sand gardens and lawns. They're also often seen near entryways. If you're ever walking with children or pets in these types of settings, keep your eyes fixed on their hands and mouths. Sago palms grow close to the ground, and because of that are easy for the little ones -- kids and pets alike -- to access. Remember, too, that the plants are spiky to the touch -- another reason to keep your distance.