Oleander is a warm- to temperate-season bush that grows quickly up to 20 feet tall. It forms a mound approximately 10 feet wide at maturity, which can become leggy as it ages. The plant produces masses of attractive flowers in pink, white, yellow, salmon and red. The lance-shaped leaves may grow up to 10 inches long. Oleanders are poisonous, so care should be taken when planting them where children and animals play. Oleanders are easy to grow and respond well to pruning. They make good subjects for training to a standard tree form.