Ask Mr. Smarty Plants

From a previous Mr. Smarty Plants answer:

"If we may take this opportunity, we would like to remind you that the Lady Bird Johnson Wildflower Center is dedicated to the use, care and propagation of plants native not only to North America but to the area in which the plant is being grown. Nerium oleander is native to Africa, Asia and and the Mediterranean. We realize it is widely used, but would like to point out one other characteristic of oleander that may be more important than taking root cuttings. Nerium oleander is one of the most poisonous plants known, with all parts of the plant being toxic. Ingestion of just one leaf can cause heart attack and death. Some of the poisons it contains are cardiotonic glycoside (oldendrine), prussic acid and rutin. Skin contact with the plant can cause severe dermatitis. Burning it will release toxins that can cause intoxication. We would recommend that it be carefully removed, wearing gloves and protective clothing, bagged and disposed of properly, NOT burned nor consigned to the compost pile, where the toxins would continue to be dangerous."

With all due respect, we would prefer that you neither grew nor propagated this plant. However, here is an article on Plant Propagation by Leaf, Cane or Root Cuttings: Instructions for the Home Gardener, from North Carolina State University.