Although some mature oleanders (Nerium oleander) may grow up to 20 feet tall, most standard oleander cultivars grow from 8 to 12 feet tall and just as wide. Two oleander cultivars, "Petite Salmon" and "Dwarf Petite Oleander," are classified as dwarfs, which only grow 3 to 5 feet tall.
"Petite Salmon" oleander, a dense, bushy shrub, grows 4 to 5 feet tall, spreading 4 to 6 feet wide. It grows in U.S. Department of Agriculture plant hardiness zones 8b through 11, yielding salmon-colored blossoms from spring through fall which are attractive to butterflies and hummingbirds. Not much distinguishes "Dwarf Petite" pink oleander from "Petite Salmon" oleander other than the color of its flowers. It grows 5 to 6 feet tall, but has the same 4- to 6-foot spread. Dwarf "Petite Salmon" oleander can be grown in USDA zones 8b through 11. Deer avoid both these cultivars, and they resist drought and mildew. Both cultivars prefer morning shade followed by full sun for the remainder of the day. They will grow in all soil types with a pH of 5 to 7.5. Although they do not like wet areas, water them deeply when the soil dries out. They will tolerate wind and salt spray. They typically do not require fertilizer. They are useful planted as a shrub border, at the base of hedges, around ponds, at the base of building foundations and in median strips and outdoor living areas.
Disease and Insects
The fungal disease Boryosphaeria dieback that typically appears when oleanders are stressed by drought or severe freezes can cause shoots and branches to turn blackish brown and die. Prune off diseased branches. The bright orange oleander caterpillar can eat much of the foliage of an oleander plant. Your best option is to prune and remove branches infested by the caterpillars. Put the infected branches in a plastic bag and freeze it for 24 hours. As a last resort, spray the caterpillars with a ready-to-use Bacillus thuringiensis spray, an organic biological insecticide that will not kill beneficial insects. Spray late in the day so the caterpillars can eat it during their nightly feeding. Repeat every seven to 10 days until the caterpillars disappear. Before and after you prune, soak your pruning tools two to five minutes in 70 percent rubbing alcohol and let them air dry.
Oleander can spread from 1 to 2 feet a year. It has escaped cultivation and become invasive in U.S. National Parks in California, Arizona, Utah, Texas, Louisiana, Mississippi, Alabama, Georgia and Florida and is listed as an invasive species by Florida.
Oleander contains the toxic substances digitoxigenin, neriin, oleandrinand and oleondroside. Do not chew its leaves or suck nectar from its flowers. Honey made from bees that have fed on its nectar can also be toxic. Do not burn parts of the plant because the smoke is also toxic. Symptoms include blurred vision, seeing halos, low blood pressure, irregular or slow heartbeat, fainting, lethargy and hives. It can be fatal. If you think have been poisoned by oleander call a doctor or the National Poison Control Center 1-800-222-1222. Do not induce vomiting unless instructed to do so.