Olive Tree Care
Olive trees are extremely drought tolerant and can survive in arid climates, clinging to rock precipices, for thousands of years. However, in order to grow at a viable rate and produce sufficient fruit for commercial production, olive trees need supplemental water in the western US due to a lack of summer rainfall. Even in the hottest European climates, there is typically some summer rain to see the trees through the growing season.
To help the trees through the growing season, it is advantageous to have an irrigation system in place. Drip irrigation lends itself particularly well to olive orchard management in areas of limited water, though flood irrigation and sprinklers are also viable options.
Most large scale orchard plantings have a single irrigation line that runs the length of the rows. The ½” or ¾” line can lie directly on the orchard floor or can be suspended above ground. Affixing the irrigation line to the tree stakes a few feet above ground allows for mowing or cultivating without harming the line and for finding leaks easily; irrigation lines can quickly and cheaply be fastened to the stake with plastic zip ties.
The length of the lines and number of emitters must be matched with the gallons/minute delivered by the pumping system. Water lines running up or down a slope may need pressure regulators to avoid flooding the bottom emitters. Emitters at ½ gal/hr or 1 gal/hr work well for olive trees, starting with one emitter on each side of the tree, placed so that they drip at the edge of the tree’s root zone, a location that will change as the tree grows. The water should not drip down the trunk leaving the crown of the tree soaked.
For a newly-planted tree, the water should drop so that it moistens the outside edge of the roots and a little into the zone beyond, encouraging outward root growth.
As the tree grows, it will be necessary to adjust the emitters. Some growers choose to place the emitter further out on the line in the beginning, using a small length of spaghetti tube drawn closer to the tree to bring the water in towards the young roots. As the root system expands, the spaghetti line is removed, leaving the emitter at a good distance from the trunk. It is also very easy to use goof plugs to seal up old holes in the line and punch new holes as you move the emitters outwards. Please seefor guidance.
Most irrigation systems in a landscape setting have the luxury of watering the entire root zone circumference of the tree. Soaker hose, drip tubes, micro-sprinklers, and other specialty designs work well when they encircle the tree. The same guidelines apply in terms of placement: water at the outer edge of the tree’s canopy. Imagine the roots as a mirror image of the canopy reflected beneath the soil surface of the tree and water to the edge of that drip line. Install a system that can grow easily with your tree.