This week a local rancher was called after someone ignorantly dumped a pile of fresh oleander cuttings at the Toll Road Trailhead in Six-Shooter Canyon - a place with obvious and abundant signs of cattle nearby. Popular as a tall evergreen landscape hedge that flowers yellow, red and white, oleander (Nerium oleander) is also highly toxic - killing 13 cattle in Greenlee County a few years back, and famously poisoning a giraffe at the Reid Park Zoo in Tucson in 2011. One report holds that a quarter pound, or about 30-40 leaves, can deliver a lethal dose to an adult horse. Oleander leaves are bitter and not palatable, but will be eaten by hungry livestock - particularly in a drought year such as we’re experiencing now. Dried, wilted leaves may be slightly more palatable than fresh leaves, and the leaves remain toxic even when they’re wilted or dried. All parts of the plant are extremely poisonous, containing 10 different cardiac glycosides - compounds that can cause cardiac arrhythmia and death. Another source reports a lethal dose of green oleander leaves for cattle and horses is just 0.005 percent of the animal’s body weight.
If oleander is part of your landscaping, make sure any and all clippings go to the landfill. And don’t ever burn them; inhaling smoke from a burning oleander also can cause poisoning. A familiar landscape plant in Phoenix, Tucson and here in Globe-Miami, oleander is also considered invasive. The pods contain seeds with hairy plumes that can be carried away on the wind for dispersal. Eradication efforts continue in the Tonto National Forest, where several clumps of oleander have grown to towering heights in Arnett and Telegraph Canyons, downstream from the town of Superior.