Oleander is an introduced, evergreen, ornamental shrub or tree (depending on pruning) 15 to 25 feet tall. Leaves are entire and leathery, essentially hairless, up to 12 inches long and 1.5 inches across. They are positioned opposite or in whorls of three or four. Each has a prominent midrib with secondary veins parallel to each other extending to the leaf margin.
The variously colored, showy, odorless flowers are produced in clusters at the ends of the branches.
Oleander is a native of the Mediterranean region and is widely planted in the southern United States. It is often found as an ornamental in eastern, central and southern Texas. It is not cold hardy and often sustains top-kill in the winter. Although it is naturalized in Texas, there are few, if any, escaped populations.
Oleandrin, a cardiac glycoside, is the most prominent toxin in oleander, which is probably the most toxic plant in Texas. As little as 0.005 percent of an animal’s body weight of dry leaves may be lethal—as few as 10 to 20 medium-sized leaves may kill an adult horse. It is toxic to all animal species, and many livestock and pets are poisoned, usually because they consumed oleander clippings or dead leaves.
The green leaves of the growing shrubs are bitter and are therefore seldom eaten. The wilted clippings and dead leaves remain toxic, are palatable and are readily consumed. Compost containing oleander leaves has also been incriminated in poisoning.
Consumption of this highly toxic plant causes cardiac failure. Signs in poisoned animals develop within 4 hours and can include: Sudden death (no observed clinical signs; Colic; Weakness; Lack of rumen muscle tone; Salivation; Very fast or slow heart rate.
Flower Color: Pink
Seed Type: Non-Encapsulated
Stem Texture: Hairless/Smooth
Growth Habit: Shrub (Woody)
Distribution : 01 - Pineywoods, 02 - Gulf Prairies and Marshes, 03 - Post Oak Savannah, 04 - Blackland Prairies, 05 - Cross Timbers and Prairies, 06 - South Texas Plains, 07 - Edwards Plateau, 10 - Trans-Pecos
Distribution refers to the ecological region in Texas that a plant has been found. You can also view a clickable map.
Book: Toxic Plants of Texas (B-6105)
Livestock Affected: Cattle, Goats, Horses, Sheep
Livestock Signs: Abdominal Pain, Abnormal Heartbeat, Abnormal Urination, Colic, Depression/ Weakness, Excess Salivation