Guavas (Psidium guajava) grow as evergreen shrubs or small trees in U.S. Department of Agriculture plant hardiness zones 9 through 11. These plants are prized primarily for their fruit, a berry that has a flavor, aroma and flesh color that vary greatly between varieties, although they are also enjoyed for their attractive bark and flowers. Guava trees can survive extended dry spells, but vegetative growth stops, and fruit set and development are affected, warranting supplemental irrigation.
Build up a berm around the drip line of a newly planted guava. Fill the space inside the berm with water about once per week for the first two growing seasons. This frequency is a general guideline. Guavas planted in sandy sites may require watering twice each week while guavas growing in soils with a high clay content may only require water once every two weeks. The berm will gradually erode away. If it does not, knock it down during the second growing season. It is not necessary to build a berm around young guavas, but this facilitates easier watering when the tree is young and regular moisture is important.
Dig a small hole about 6 inches deep just outside the guava's drip line, and feel the soil at this depth. If the soil feels completely dry to the touch, water the guava. Typically, an established guava will require a deep watering every one to two weeks in the summer and once per month in winter months.
Lay a soaker hose on the ground around the guava tree or use a garden hose turned on to a trickle to water an established guava tree. Apply the water slowly enough that it penetrates the soil surface without running off.
Push a metal rod such as a piece of rebar into the ground after watering to test how deeply the water penetrated. Moist soil is easier to push the rod through. The rod becomes more difficult to push into the soil where the soil is still dry. Immediately following watering, the soil should be moistened to at least 12 inches below the soil surface. If the metal rod becomes difficult to push into the ground at a shallower depth, water the guava more.
Monitor the guava tree for signs of drought, and increase the frequency of irrigation or the quantity applied with each irrigation, if needed. Drought stress appears as wilted leaves and young twigs, decreased fruit set and smaller fruit size.