Planting a fruit tree is a long-term investment, and the depth at which it is placed is the most important factor determining its success. The difference between a thriving, productive orchard tree and one that struggles often comes down to just a few inches of soil. The goal is to position the tree at the precise vertical location that allows its specialized tissues to function correctly. Achieving this perfect alignment is foundational for the tree’s overall health, productivity, and longevity.
Identifying the Reference Point for Depth
The correct planting depth is determined by two distinct features: the root flare and the graft union. The root flare is the natural, visible widening of the trunk where it meets the roots and must sit exactly at or slightly above the finished soil grade. The bark in this region is not adapted to constant subterranean moisture or low oxygen conditions.
For most fruit trees, the graft union is another critical reference point. This is the swollen or scarred area where the desired fruit-bearing variety (scion) was joined to the rootstock. To maintain the dwarfing or disease-resistant benefits of the rootstock, the graft union must be kept several inches above the final soil line, typically two to four inches.
Consequences of Planting Too Deeply
Planting a fruit tree with its root flare buried is one of the most common mistakes, leading to a slow and often fatal decline. The roots that anchor and nourish the tree require oxygen, and burying them even slightly reduces the necessary oxygen exchange, causing suffocation and stunting the tree’s vigor.
When buried, the bark on the trunk and root flare remains constantly wet, leading to decay and trunk rot. This continuous moisture encourages fungal infections that can girdle the tree by damaging the vascular tissues. If the graft union is buried, the scion wood may develop its own root system, which negates the specific benefits of the specialized rootstock.
Consequences of Planting Too Shallowly
While planting too deeply is a major concern, planting a tree too shallowly also creates significant problems for establishment and survival. When a tree is positioned with its upper roots exposed or very close to the soil surface, the root desiccation risk increases substantially. These fine feeder roots, which are responsible for absorbing water and nutrients, can dry out quickly, especially during periods of hot, windy weather.
A shallow planting depth also compromises the tree’s structural stability and anchoring. Without sufficient soil depth to hold the primary structural roots securely, the tree may become unstable and be prone to tipping or windthrow, particularly as it grows larger. Additionally, roots near the surface are more susceptible to temperature extremes, facing scorching heat in the summer and damaging freeze-thaw cycles in the winter.
Depth Adjustments for Different Tree Stock
The proper preparation for planting depends heavily on how the tree was grown in the nursery, requiring different adjustments to meet the correct depth.
Bare-Root Trees
For bare-root trees, the original planting depth is often visible as a slight color or texture change on the lower trunk. The goal is to set this previous soil line slightly higher than the new final grade to account for natural soil settling after watering.
Container-Grown Trees
Container-grown trees are frequently potted too deeply by the nursery. Before planting, the gardener must remove the excess soil or mulch from the top of the container root ball to locate the true root flare. If the tree is planted based on the container’s surface level without this correction, it will be inadvertently planted too deep. It is also important to loosen any circling roots on container trees to encourage them to grow outward into the native soil.