When it comes to watering trees, shrubs, and flowers there is not a simple formula. Temperature, rainfall, soil type, amount of sun/shade, and mulch will all play a role in the watering schedule of plants. A key factor, however, is the soil texture. Clay soils can hold up to three times more water than sandy soils. Try one of these two methods to check if you need to water.
Method #1 – Check soil by moving stone or mulch aside and inserting your finger into the soil up to the second knuckle. You want moist soil, not wet. If there is little or no moisture in the soil, water.
Method #2 – Use a moisture meter. These meters will give a moisture reading when inserted into the soil. Again, if there is little or no moisture in the soil, watering is needed. When watering is needed, water to soak the soil deeply, not just to get it wet. Deep watering leads to a desirable long root system and less watering. There are two good ways of doing this. One way is to set a hose on trickle and let it sit at the base of the plant for 15 to 20 minutes. Another way to water deeply is to place a 5 gallon pail with a hole in the bottom of it next to the plant, fill the pail with water, and leave it sit until the water is gone. As the water seeps out of the hole in the pail, it is absorbed into the soil. Annuals and perennials have a shallow root system; therefore, the soil for these plants should be check more frequently.