Poison Ivy may be number one on everyone's short list of plants to watch out for in the yard. Knowing how to identify poison ivy (Toxicodendron radicans) is critical to steering clear of this plant, which can cause reactions in humans ranging from a red, itchy rash to blistering or even anaphylaxis.

The leaves of poison sumac sometimes have black or dark brown spots that are filled with urushiol. In autumn, the leaves turn red, yellow and pinkish. Poison sumac typically grows into a woody shrub with glossy cream or pale yellow berries.

Dicentra spectabilis, or bleeding heart, is native to woodlands and is a shade loving perennial. The name bleeding heart describes the unique flowers, which resemble tiny pink or white hearts with drops of blood at the bottom. The roots and foliage of bleeding heart contain alkaloids that are toxic to animals if eaten in large amounts.

All parts of the azalea are dangerous if eaten in great quantities. Ingestion of the toxin contained in the plant, andromedotoxin, can result in progressive paralysis, coma and death. But human fatalities from eating this plant are rare.