How to identify poisonous plants Toxic plants to keep out of reach of children and pets. Your backyard may be your pride and joy, but are there poisonous plants hiding out among the greenery? “Leaves of three, leave them be” is a useful rhyme to help you recognize poison ivy and oak and avoid the itchy symptoms they bring, but that’s just the beginning to recognizing toxic plants.Many others don’t fit into an easy characterization. Some of the most prized decorative plants and flowers can be quite harmful if ingested. If you have young children and pets, take care to steer them away.Here’s what to look out for:Poison sumac: Less common than poison ivy and poison oak, poison sumac is actually more toxic than the other two. Contact with this poisonous plant can cause a rash and swelling.Foxglove: All parts of this pretty, bell-shaped flower are poisonous, and could even be lethal, if eaten. Foxglove (also known by its Latin name, Digitalis) grows wild throughout the United States and is cultivated in gardens because its white, creamy yellow, pink or rose flowers make an attractive addition. Because of its toxicity — bear in mind that a powerful heart medicine is derived from the plant — children must be carefully watched around it. It is also toxic to a range of animals, including livestock, cats and dogs.Aloe: This is a great plant to have on hand as a natural salve for burns. However, it can be harmful to pets if ingested and can cause vomiting, diarrhea and tremors. If you have this plant, keep it at paw’s length.Hydrangea: A common shrub with clusters of flowers in pink, purple, white or blue, hydrangeas can be toxic to people and pets if large quantities are eaten. Symptoms include stomach ache, nausea, vomiting and sweating, but it’s usually not deadly.