Oleander is an evergreen shrub or small tree in the dogbane family Apocynaceae. The flowers grow in clusters at the end of each branch; they are white, pink, red or yellow, 1-2 inch diameter, with a deeply 5-lobed corolla with a fringe round the central corolla tube. They are often, but not always, sweetly scented. Oleander is one of the most poisonous plants known. The entire plant, including the milky white sap, is toxic, and any part can cause an adverse reaction.