What does leaves turning brown mean on an oleander?

Brown leaves on an oleander can indicate several issues, including inadequate watering, either overwatering or underwatering, or exposure to extreme temperatures. Fungal infections or pests may also cause browning. Additionally, nutrient deficiencies, particularly in potassium or magnesium, can affect leaf health. It's important to assess the plant's watering routine, environmental conditions, and overall care to determine the exact cause.