Trees respond to wounds by compartmentalising tissue -- effectively forming a callus and sealing themselves off from invading elements, pathogens and pests. Cutting an entire tree off at the trunk base mimics any pruning or coppicing wound on a branch. The tree's root cells and those left in the trunk base can differentiate and become leafy shoots. Regrowth shoots that occur from felled trees are termed water sprouts or suckers.
The ability of a tree to resprout branches or shoots from the roots after being chopped down varies by species. Some vigorous, fast-growing tree species like red maple, powderpuff tree or box elder readily rejuvenate after being cut down or toppled after a storm. Others, like spruce, pine, ash, oak or palm, may not rejuvenate at all. The health and response by the trunk stump and root system determine if the tree rejuvenates.
When Does the Tree Die?
All parts of a healthy tree are alive, from the leaves and branches all the way down to the roots. Simply cutting off the top of the tree doesn't immediately kill the entire plant. The underground roots continue to live and absorb water and nutrients. It's only when the root cells become impoverished from a lack of carbohydrates made by leaves that the root system, and tree, finally dies. As long as the roots survive, it's possible for a sucker to form from a surface root or the trunk stump and begin to grow and make food in its leaves.
Environmental conditions can affect how quickly the felled tree's roots die and if suckering occurs. Sick, diseased or weak-growing trees are less likely to regrow after being cut down. They simply do not have the energy, resources or vigour to rejuvenate. Likewise, cutting down a tree when it is stressed from drought, or just before winter, can make regrowth more challenging. Lack of soil moisture, food-making leaves and conducive warmth combine to further kill remaining root tissues before the next growing season. Diseases or herbicides that invade or are absorbed into the trunk wound and are translocated through the roots will kill the tree.
New Tree Development
Tree species with a natural disposition to sucker after being cut down and in favourable environmental conditions can regrow into seemingly new plants. At first, the trunk may sprout multiple suckers, each producing food in leaves and receiving water and nutrients from the massive root system. Within a couple of months, the regrowth looks like a shrub. Eventually, one or two suckers dominate, growing taller and more vigorously than the others, becoming the new tree trunk. For healthiest growth, a gardener cuts off all suckers except one. This lone branch has the best structure, form and base to become the new tree on the old root system.