The key to growing healthy, vibrant oleanders is to start with healthy plants purchased from a reputable nursery. When choosing oleanders, look for dense, bushy plants that feature dark green leaves and thick stems. Avoid any oleanders that have yellowing or damage. Before taking your oleanders home, inquire about the oleander plants' growing conditions. Ask about the temperatures they were grown in, their watering and fertilization routine, and the amount of light they received. When you get your oleander home, you will initially need to mimic these conditions before gradually introducing changes in light, routine and temperature; failure to do so may subject your oleander to leaf drop or shock.
Dig a hole that is three times as wide but just as deep as the oleander's current container.
Mix the excavated soil with peat moss in a 2:1 ratio.
Carefully remove the oleander from its container.
Plant the oleander in the hole so that the top of its root ball is level with the surrounding soil.
Backfill the hole with your soil mixture.
Water the soil so that it is quite moist but not soaking. Keep the soil moist while your oleander is establishing itself. Once your oleander is established, you can give it supplementary water if it does not receive one to two inches of rainfall per week. Oleanders are quite drought hardy and really only need water when the soil dries out.