When a tree is cut down, whether the extensive underground root system dies immediately is complex, depending on the tree species and the removal method. The roots do not instantly vanish but begin a process of slow decline or, often, an aggressive attempt at survival. Understanding the fate of these roots is important for managing a landscape after tree removal.
The Biological Fate of the Root System
A tree’s roots are entirely dependent on the canopy for their energy supply, which is produced through photosynthesis. Once the trunk is cut, the leaves and branches—the tree’s food factories—are gone, immediately halting the supply of sugars, which are the tree’s primary energy source. This severe disruption means the roots are cut off from their nutrition.
The root system does not die immediately because it relies on stored carbohydrates, primarily starch, accumulated during the tree’s life. These energy reserves are located within the root tissues and the remaining stump, allowing the root system to survive for a period. Root death is a process of starvation, as the roots slowly deplete their starch reserves while attempting to generate new growth to restart photosynthesis.
The extent of energy depletion depends on the tree’s size, age, and species, often taking many months to exhaust stored energy. Without a new canopy to replenish the supply, the root cells eventually cease to function. The large mass of woody root material then becomes subject to natural decomposition.
The Mechanism of Survival: Stump and Root Sprouting
Many tree species have a natural response to severe injury like felling: attempting regeneration from dormant buds. This survival mechanism is common in deciduous trees such as maples, oaks, willows, and poplars. These species possess specialized cells that activate to produce new shoots, effectively trying to form a new tree.
This regrowth occurs in two distinct forms: stump sprouts and root suckers. Stump sprouts emerge directly from the remaining trunk or the root collar, utilizing dormant or adventitious buds near the cut surface. Root suckers originate from the lateral roots that spread away from the main trunk, sometimes emerging many feet away from the original tree location.
The appearance of these sprouts indicates that the root system is still alive and actively drawing upon stored energy reserves. If these sprouts are allowed to develop leaves, they begin photosynthesizing, creating new sugar to replenish the root system and potentially allowing it to survive for many years.
Accelerating Root Death and Preventing Regrowth
To prevent regrowth and accelerate the root system’s demise, property owners use two primary methods for managing the remaining stump and roots. Mechanical removal using a stump grinder is a highly effective physical approach to eliminating the central energy source of the roots. This process involves grinding the stump several inches below the soil grade, which severs the main connection point between the large roots and the stump.
Grinding the stump prevents stump sprouts and significantly reduces the woody material available to store starch, speeding up the starvation of connected roots. While grinding does not remove the entire root system, the severed roots, now isolated from the central energy source, begin to decay much faster.
Alternatively, chemical treatment involves applying a concentrated, systemic herbicide, such as glyphosate or triclopyr, directly to the freshly cut stump. The most effective application is to drill holes into the stump surface and apply the chemical to the outer ring of the wood, just inside the bark. This vascular tissue transports the herbicide down into the root system, chemically killing the remaining stump and connected root mass.
A systemic herbicide application is particularly useful for species prone to extensive root suckering, as the poison travels through the connected root network. It is important to apply the chemical immediately following the cut, because the wood seals quickly, preventing effective absorption and distribution of the herbicide throughout the roots.
Decomposition and Long-Term Consequences
Once the root system has died, whether through natural energy depletion or chemical treatment, decomposition begins. Microorganisms, primarily fungi and bacteria, colonize the dead wood, gradually breaking down the dense cellulose and lignin structures. The time required for this process varies significantly, often taking five to ten years for smaller roots and potentially decades for large, structural roots, especially those from dense hardwood species.
This decay process contributes organic material and nutrients back into the soil, but it also presents long-term considerations. As the mass of dead wood decays, it takes up less space, which can lead to localized soil settlement or uneven ground. Decaying wood can attract certain pests, such as termites or carpenter ants, and may also become a host site for wood-rotting fungi, including some that cause root rot disease in nearby living plants.