Mature citrus trees can need as much as 17 gallons of water per day in winter and 135 gallons daily in summer, according to the University of Arizona. Curling or wilting leaves usually means a lack of water, though in some cases it's a sign of overwatering or other conditions. Container citrus trees require more watering than ground plants. You'll also need to water more often in hot climates, and some citrus plants more than others. For example, oranges require 20 percent less water than lemons and grapefruit, according to the University of Arizona.
Use a trowel to dig a 6-inch deep hole near the citrus plant. Use your finger to test if the soil is dry or moist. If dry, the plant needs watering. If damp, the plant should have enough moisture and the wilting may be the result of too much watering or a plant disease.
Pile up dirt in a ring shape 6 inches deep and 6 inches thick, according to Texas A&M University. Build the ring a foot wider than the crown and foliage of the citrus tree. Ensure there are no gaps in the ring.
Fill inside the ring using a hose, being careful not to direct a strong jet of water at the ring edges. Water in the morning before the hottest part of the day. Allow the water to soak into the ground.
Water the plant every seven to 28 days, depending on your location, the soil type and the citrus variety. (Despite the recommended needs, the University of Arizona discourages watering every day.) Fill the watering ring up each time. In some situations, you may need to water twice a week. Check the top 6 inches of the soil before watering. If damp, wait until dry. This helps prevent soil-borne diseases, according to the University of Arizona.