The olive tree is an evergreen native to several Mediterranean and Middle Eastern countries. Its fruit has been a staple crop for several thousand years and garners several mentions in the Bible. An olive tree's root system is extensive in search of water. Its root system is one of the main reasons for the plant being so drought resistant.
An olive tree's root system distributes nutrients differently depending on the type of soil. In sandy soil, which drains rapidly, an olive tree's root system must conserve water to survive and will therefore not yield a high crop. A tree planted in clay soil tends to produce a larger olive crop because the soil holds water better allowing the root system to turn its attention to growing.
According to Olive Australia's website, a newly planted olive tree requires about two gallons of water per week to properly establish its root system in the soil. Water should be applied in one weekly dose in the course of the summer with staggered waterings during the winter months. An olive tree's root system is highly resistant to drought and may continue to thrive even if watering is less frequent than recommended.
Olive tree roots that are overwatering or flooded may be susceptible to bacterial or fungal infection. Root rot infects the root system of olive trees, which are stressed due to overwatering. Root knot nematodes and citrus nematodes may infest an olive tree's root system causing stunted growth and reduced foliage. Maintaining well-drained soil is a key factor in maintaining optimal olive tree health and discourages the presence of bacteria and pests.
Olive tree root systems can span as wide as 16 feet at maturity with some developing an even wider span. For this reason, olive trees planted in orchards are given as much as 36 feet between them to accommodate the potential expanse of the root systems. When olive tree root systems are allowed to grow too close to each other, they compete for the same soil nutrients.