High water use plants like roses need to be irrigated about twice as often as established arid region plants. Root depth Root depth also has a major impact on how often plants need water. The deeper the roots, the less frequently you will need to water. Encourage a deep, drought-resistant root zone by watering deeply. If your soil is shallow, compacted or sandy you will have to irrigate more frequently.
Leaves turn a lighter shade of green or turn yellow.
Young shoots are wilted. Leaves are green yet brittle. Algae and mushrooms are growing. Under-watering Soil is dry. Older leaves turn yellow or brown and drop off.