Citrus trees have a shallow root system that can dry out rapidly during the heat of summer. Moisture stress can adversely affect fruit quality and tree health, so it’s important to keep the soil or potting mix moist with regular and deep watering. If you find that the soil is not absorbing the water, no matter how much watering you do, then apply a wetting agent like Yates Waterwise Granular Soil Wetter. This helps improve soil moisture levels by breaking down the waxy, water repellent layer that can develop on the surface of soil or potting mix and allows water to better penetrate down into the root system.
Citrus in pots will dry out much faster than trees growing in the ground, so more regular watering of potted trees will be required.
Take the additional step of applying an organic mulch, like straw or bark chips, around the root zone. This helps keep the soil or potting mix moist, as well as protecting the root system from baking summer sun. Keep the mulch a few cm away from the trunk. This helps improve air circulation and reduce the chance of fungal diseases. Also remove any grasses and weed growth from around the tree’s root zone. Weeds steal valuable water and nutrients from the tree and reduce air flow around the trunk.