Q. We had six 24″ box bay laurel trees and one 24″ olive tree planted in April of 2021, three years ago. We water once a week for one hour with four, two gallon per hour emitters in the spring. We are not sure if they are doing well and would appreciate your expert advice.
A. Thank you for telling me how you are irrigating these trees. If it were me, I would flood the area around the tree, a single time, with water now. Don’t wait. Use a $12 stationary sprinkler at the end of a hose and adjust the watering pattern from six to eight feet. Water this way for one hour.
Next, I would increase the four emitters to four gallons per hour rather than two gallons per hour. I would still water for one hour. As trees get bigger, they need more water. I believe you did not give these trees enough water when they needed an increase in water.
A normal response to a lack of water is leaf drop and thinning of the canopy. I doubt it is a disease problem. I would first guess it’s not getting enough water as temperatures increase. This is normally taken care of by increasing the number of times you water per week. In your case, I think the two gph emitters did not release enough water. Replacing the emitters is sometimes a better solution than increasing the water output for ALL the plants. This way your watering time does not change.
Some people plant these trees in dry soil. Make sure they are planted “wet”. Watering now with a stationary sprinkler wet all of the roots immediately. Make sure those 4 gallons per hour emitters are from six to twelve inches from the trunk of the trees. All of the soil should be wet between irrigations. These are not desert trees (xeric) but both are water loving mesic trees.
Just for your information the olive tree will grow about 30 feet tall if left alone (they should be planted no closer than 20 feet apart). Olive trees can handle the heat. The bay laurel will grow about 20 feet to 25 feet tall but struggle with extreme heat. Both are considered “mesic” in their water use.