Q: I plan to buy a 15-gallon fruitless olive tree. Please tell me how much water daily or weekly it should be given once planted.Β The irrigation system in place for shrubs and trees comes on Monday and Friday for one hour. There are two black adjustable 10-gallon emitters where the tree will be planted. If the tree requires daily watering instead of the two days, I can water with a hose. When the temperature increases to 90 and higher, the irrigation system waters Monday, Wednesday, and Friday for two hours.
A:Β Olive trees should receive water every seven to 10 days in the summer to a depth of 24 to 36 inches. In the spring and fall, you can water every 10 to 14 days and in the winter, you can water every 14 to 21 days. Typically, two emitters can supply new trees as you described. As trees get older and their root zones increase in size, adding an emitter to the increasingly wider circle of drip irrigation would be appropriate every few years. The depth of irrigation can be measured with a soil probe. The schedule you are using now is watering too often and will encourage shallow root growth that will be more susceptible to our blast furnace summer heat.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions may be emailed to
