Description
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.
Distribution and habitat
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 topkill in the winter. Although
it is naturalized in Texas, there are few, if any, escaped
populations.
Regions: 1,
2, 3,
4, 5,
6, 7,
10.
Toxic agent
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.
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Livestock
signs
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
Integrated management strategies
Prevention of oleander poisoning is easy and absolute: Do
not plant any on your property. Remove plants that are present,
and do not allow animals access to removed plants or clippings.
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