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Nerium oleander, or simply oleander, is a shrub or small tree that was introduced from the temperate Mediterranean area of the Old World. It was widely utilized and is still a component in landscaping projects throughout the southern U.S. and Mexico because of its showy, brightly colored, odorless flowers of many colors.
Has opposite or whirled, leathery leaves that can reach 12 inches long and 1 1/2 inches wide. They have a prominent midrib with secondary veins that parallel each other, extending to the leaf margins.
Produces various colored flowers, ranging from white to red, in clusters at the end of the branches.
Often found on ranches around old homesteads that have long since disappeared from the landscape.
Oleander contains a highly toxic chemical known as a cardiac glycoside and is perhaps the most toxic plant in Texas. It can be lethal in very small doses and causes cardiac failure. The plant is toxic to all animal species.
The leaves are very bitter in growing plants and are usually not consumed by grazing animals. However, dead leaves or clippings can still be a problem because they remain highly toxic even when dried — a single leaf can kill an adult.
Poisonings have been reported from simply handling the plant, inhaling the smoke of burning trimmings, and coming into contact with the milky sap or water used to keep the flowers fresh in vases. The plant and its sap have been used in Africa as a poison to soak dart and arrow tips and used as a weapon in tribal warfare.
Oleander does have one use that may be beneficial to society: There is a species that produces medical alkaloids that are used in cancer treatments.
If oleander is found on farms and ranches, it should be identified and noted to avoid poisoning of livestock and pets.
Editor’s note: Kent Ferguson, retired rangeland management specialist from USDA Natural Resources Conservation Service (NRCS), is providing us with plant identification photo stories to help ranchers identify those forbs, forages and species growing in the pastures. Additional photos provided by USDA NRCS.
Common Oleander is excerpted from the May 2017 issue of The Cattleman magazine.