The underground structure of a tree is an intricate network designed to support its growth. Tree roots have two primary functions: providing physical anchorage to resist wind and gravity, and absorbing water and dissolved nutrients from the soil. This system is divided into two main types: the woody, long-lasting structural roots and the fine, non-woody absorbing roots.
Structural roots grow thick and wide, forming the foundational framework that stabilizes the tree. Absorbing roots, often called feeder roots, are hair-thin and densely concentrated near the soil surface, typically in the top 12 to 18 inches, where oxygen and moisture are most readily available.
How Trees Respond to Root Damage
A common misconception is that a cut root will simply regrow its severed tip, but this is not the case for woody roots. Once the growing tip of a structural or transport root is sliced, that specific point of the root stops growing outward. The tree does not possess a mechanism to regenerate the exact severed end.
Instead of regeneration, the tree employs a compensatory strategy to replace the lost function. Following an injury, the tree initiates the formation of new, specialized growths called adventitious roots. These new roots emerge from the wound area behind the cut, or from the main root crown, in response to the loss of water and nutrient uptake capacity.
This new root growth is a form of repair, aiming to establish a new absorbing surface to compensate for the damage. Minor root damage can often be overcome by the tree, which allocates energy to quickly produce these new feeder roots. However, removing a large structural root can compromise the tree’s stability, and the subsequent compensatory growth is often too slow to prevent structural failure or decay from setting into the wound site.
The Fate of Roots When a Tree Is Removed
When a tree is cut down at the trunk, the remaining root system, now deprived of its leaves and canopy, no longer receives the carbohydrates needed to sustain life. The roots of the dead tree cease to grow and instead begin a long process of decomposition driven by fungi and bacteria in the soil. The timeline for this natural decay varies significantly, depending on the root size and the tree species.
Roots from softer woods, such as pine, may fully decompose in 15 to 20 years. The dense, tougher structural roots of hardwoods like oak or maple can persist for 40 years or more. During this period, the decaying roots gradually release stored nutrients back into the surrounding soil. This is distinct from the phenomenon of suckering, where a tree’s roots remain alive even after the trunk is gone.
Certain species, including poplars, willows, and some fruit trees, have a strong genetic tendency to sprout new shoots—suckers—directly from the remaining living root system. These shoots are genetically identical to the original tree and will continue to grow until the root’s stored energy is fully depleted. To prevent this vigorous regrowth and accelerate the decay process, homeowners often choose stump grinding or applying a chemical treatment to the stump.
Environmental Factors Affecting Root Growth
The direction and speed of any root growth, whether compensatory or routine, are dictated by external conditions in the soil. Water availability is a primary driver, with roots naturally elongating into areas of higher moisture. This pursuit of water is why roots may exploit existing cracks in foundations or sewer lines that are leaking.
Roots do not seek out and break into solid, intact infrastructure. Instead, they capitalize on the environment created by loose soil, existing cracks, or leaks, which provide both moisture and the necessary oxygen for growth. Roots will be severely restricted in soils with high bulk density, which is often a result of heavy compaction from construction or traffic.
Compacted soil limits the available air pockets, restricting the oxygen required for root respiration and creating a physical barrier to expansion. In these conditions, trees often develop a shallow, wide-spreading root system that stays close to the surface where oxygen levels are higher. Nutrient availability also influences root density, as the fine absorbing roots proliferate most successfully in nutrient-rich zones of the soil.