Are Apple Tree Roots Invasive?
Apple tree roots will grow where their needs are met and spread to areas that hold nutrients, water and oxygen. Apple tree roots grow to different depths and lateral sizes depending on the type of rootstock, type of soil and environmental conditions, but mainly grow more shallow and out laterally.
Apple tree roots can grow up to twice as large as the canopy is wide and compete for nutrients, water and oxygen with nearby plants. However, apple tree roots are not invasive or aggressive, and do not have the strength to cause foundation damage to homes or invade sewer pipes.
How Do Apple Trees Roots Form?
As apple trees germinate from seed, a taproot emerges to anchor the delicate plant into the soil. After only a few years, the embryonic taproot dies back while the plant is still young and growing and the root structure changes to a wide-spreading fibrous root system with only a few vertical, deep anchoring roots. This forms a mass of fine roots, with no distinct tap root.
Apple trees generally contain a few vertical, deep roots that grow straight down into the soil. These deep roots are able to reach deep moisture reserves to sustain the tree during times of drought and mine for nutrients. They also serve to anchor the tree to the ground during extreme weather.
Within three years, under ideal soil and moisture conditions, a full sized standard rootstock can grow vertical roots up to 20 feet deep (6 meters).
Apple tree fibrous roots grow radially and horizontally from the deep roots and penetrate the soil in all directions away from the plant in search of moisture and nutrients. They are generally close to the surface of the soil within the top 3 feet (1 meter). Fine root hairs develop from the fibrous roots to take up water and nutrients from the soil near the surface, called feeder roots, which branch out four or more times to form fans of mats of thousands of fine, short, non-woody tips measuring between 0.2-1mm in diameter, and 1-2mm long. These feeder roots are the source of the majority of water, nutrient and oxygen absorption for the apple tree.
Fun Fact: At the end of the first year, a young apple tree can grow over 17,000,000 feeder roots, with a total length of over a mile long.
Feeder roots grow off the fibrous roots, and usually grow upward into the top few millimetres of soil. The feeder roots of apple trees will compete for water and nutrients with nearby plants and turf, which is why it is crucial to mulch the base of young apple trees in order to retain moisture and prevent shallow rooted turf and weeds to grow around the base of the apple tree, robbing nutrients from the feeder roots. Grass and weeds that grow around the base of young apple trees will stunt the growth of the apple tree when it needs it most in the first few years of root development.
Root systems with few feeder roots or dried root systems can slow shoot growth until an active system of feeder roots can be established, since these feeder root are responsible for most of the water, oxygen and nutrient uptake from the soil. To have good water, oxygen and nutrient absorption, there needs to be constant growth of new generations of feeder roots as older roots dry up near the surface of the soil or die off from damage or soil predators who chomp on the juicy feeder roots.
In some cases, the root system of an apple tree can grow to be twice the width of the canopy of the tree.
The rootstock of an apple tree will determine how large the mature tree will become, how quickly it will set fruit, and also how slow or limited the root mass will grow, with some rootstocks being more vigorous than others.
For example, an M.9 rootstock and an M.26 rootstock will both produce semi-dwarf apple trees, but the M.26 rootstock is more vigorous, and thus will produce a larger fibrous root mass. M.9 rootstock will produce a tree that would require staking, versus an M.26 rootstock which will have better ground anchorage.
Read our guide to learn more about the different rootstocks and how they affect apple tree growth.
When Do Apple Tree Roots Grow?
Both the lateral and fine roots of the apple tree grow rapidly throughout the spring in order to mine for water and nutrients it needs to bud out and create leaves and flowers. As the flowers get pollinated in late spring, the energy focus is placed on developing fruit, and root growth decreases.
Once the summer hits, the roots will stop growing while they focus on supplying water and nutrients to the tree for growth and fruit production.
Throughout the fall and winter once the branches go dormant, the feeder roots will start to die back, but the fibrous roots will continue to grow until the ground starts to freeze. Roots do not go dormant like the above ground apple tree branches do, they will continue to grow and mine for nutrients to store for next season’s growth and development. This root growth also contributes to good anchorage of the tree for the following seasons heavy crop of apples.
Another reason why it is important in the first few years of planting an apple tree to pull off any flowering buds in order to prevent the tree from focusing its energy on producing apples. Instead, the focus should be on growing a large healthy root system that could sustain the tree through drought, provide good anchorage to the ground against extreme weather conditions, and provide an abundant harvest in future years.
Can Apple Tree Roots Cause Damage?
Apple trees do not have aggressive or invasive root systems that could cause structural damage to foundations or sewer pipes, so they are safe to plant near your house without worrying about damage caused by the roots.
In fact, sometimes planting an apple trees about 6-8 inches from the wall of the house is a good idea, especially south facing walls that are sheltered and relatively warm. Trellising the branches to lay flat against the wall in a fan shape is a style of fruit tree training called ‘espalier’.
What is the best soil for apple tree roots? The best soil for apple trees are well draining medium-clay to sandy loam, fertile soils with slightly acidic to neutral pH between 5.8 and 6.5. Read our guide to learn more about the best soil types for apple trees.