Oleander (Nerium oleander) is a widely cultivated ornamental shrub known for its beauty and resilience. Understanding its root system is important for successful cultivation and managing its growth. This knowledge helps in making informed decisions about where and how to plant this shrub to ensure its health and prevent potential issues.
Characteristics of the Oleander Root System
The oleander root system is fibrous, dense, and extensive, allowing the plant to establish itself firmly. These roots are tough, capable of growing among rocks and other obstacles. Oleander is “flat-rooted,” meaning its root development primarily expands outward in width rather than downward into significant depth. This characteristic contributes to the plant’s drought tolerance and its ability to thrive in poor soil conditions. Its vigorous roots actively seek out moisture and nutrients, supporting its survival in challenging environments.
Root Depth and Spread
Oleander roots extend horizontally, well past the shrub’s canopy. For instance, roots of an 8-foot shrub can spread approximately 4 feet beyond its drip line. They can travel 30 feet or more to reach moisture sources like water or sewer lines.
Soil type, water availability, and the plant’s age influence the root system’s size and reach. Mature oleanders can grow from 8 to 19 feet tall and 6 to 10 feet wide, with some varieties reaching up to 25 feet. The development of suckers from the roots further contributes to the plant’s extensive underground network.
Implications for Planting and Landscape Design
The robust, spreading nature of oleander roots necessitates careful consideration during planting and landscape design. Its aggressive root system can damage pavement, pipes, and building foundations. For example, roots have been reported pushing against block fences and causing structural damage.
Oleander roots actively seek moisture, making them hazardous to underground pipes and septic systems. They can penetrate small cracks in pipes, growing inside to create blockages or breaks. Even a minor leak in a pipe can attract these roots, regardless of the pipe’s depth.
To minimize damage, maintain a lateral distance of at least 3 meters (approximately 10 feet) between oleander plants and known pipes. Guidelines suggest planting shrubs at least 12 feet from sewer lines, increasing to 18 feet for tree-trained oleanders. When planting near walls, a distance of 2 to 3 meters (approximately 6.5 to 10 feet) is advisable, especially if underground pipes are present.
The vigorous root system can also lead to competition with other garden plants. As an alternative, oleander can be grown in containers, which restricts its root spread. For container planting, selecting a wide pot, typically between 14 and 24 inches, with adequate drainage, is more suitable than a deep one.
Managing Oleander Roots
Managing oleander roots involves proactive strategies. Installing root barriers can prevent roots from encroaching on structures or underground utilities. These barriers, typically made of rigid plastic, are designed to be installed deeply (from 12 to 36 inches) to direct root growth downward and away from vulnerable areas. Careful selection of planting locations is important, ensuring the oleander is situated far from foundations, pipes, and septic systems.
If root pruning becomes necessary, it can be done by digging a trench and cutting the roots; consulting with an arborist is recommended for extensive operations. Accessing roots for pruning or removal is often made easier after the main shrub has been stump-ground.
Complete removal of an established oleander is a difficult task due to its strong and extensive root system. Left-behind root sections can resprout, necessitating thorough removal, which may involve chemical intervention, specialized tools, or brute force. Deeply watering the soil around the plant before attempting to dig out roots can facilitate the process. Regularly removing suckers that emerge from the roots helps prevent them from diverting the plant’s energy and impacting its flowering.