Although Oregon has a coastal climate and parts of the state are USDA zone 9, the state's mountainous terrain has many micro climates. Because the tree sustains damage when temperatures drop below 17 degrees Fahrenheit, olives may only be grown in the ground along the state's narrow coastal zone 9. In zone 8 or colder climates, olives should be grown in containers.
Choose a location in full sun with good drainage. Olive trees left in standing water will sustain root rot. Orient your trees plot north-to-south. Locating your tree near the south side of a wall or building will help it take advantage of radiant heat from that structure, as well as protecting the plant from damaging winds.
Dig between 15 and 20 sub-samples of soil by taking 1 qt. of soil using an auguring tool to dig as deeply as 9 inches from each location. Mix the samples in a bucket, pick out debris and allow the sample to dry.
Contact your local Oregon State University Extension service for a list of approved soil-testing facilities. Contact each facility to determine rates, turnaround times and the tests they provide. Your soil test should tell you the structure of your soil and pH, as well as how to improve the structure and pH to grow olive trees.
Break up soil using a rototiller or spade. Spread your amendments over the soil in a 4-inch layer. Good amendments for sandy coastal soil include compost and peat moss to retain moisture. Olive trees grow well in many soil types and in a wide pH range of 5.5 to 8.5. Add lime to raise the pH of Oregon coastal soil, or sulfur to lower it. Mix the amendments into the soil with a rototiller.
Open a planting pocket for your tree that is twice as wide as the root ball, but no deeper. Place the root ball of your olive tree into the hole and fill in the sides with soil. Pat the ground to release air pockets and fill in the space with more soil.
Water the tree every 10 days so the roots are as wet as a wrung-out sponge for the first year. Once the roots become established, you may gradually reduce the amount of water until it is no longer needed. Olive trees are very drought-resistant and seldom need watering when established.
Fertilize the tree in spring with a balanced, granulated fertilizer (10-10-10) by spreading the fertilizer around the drip line of the tree. Use the fertilizer amounts recommended by the fertilizer manufacturer. Fertilizer concentrations vary among manufacturers.