Understanding the depth to which tree roots can extend is essential. This knowledge is crucial for protecting your utilities and plumbing systems against damage caused by roots. Additionally, it plays a significant role in promoting the health of trees.
Tree roots typically grow within 60 cm from the soil’s top. It is unlikely for them to grow more than 2 meters deep. This is because they tend to restrict their growth to depths at which they can get easy access to oxygen, nutrients, and moisture. And this is usually nearer the surface. However, there are trees like The Shepherd’s tree and The Wild Fig whose roots have recorded depths of over 70 meters1.
Here is what you should know about tree root growth.
Typically, tree roots usually grow up to about 1.5 times the diameter of the crown.
However, they can grow even further. This is especially true when there is a need for moisture or nutrients. This, in addition to the presence of soil conditions that allow for easy growth, can lead to individual roots up to more than 4 times the diameter of the tree’s crown.
Which trees have the deepest roots?
The Shepherd’s tree, a tree that naturally grows in the Kalahari desert, has a recorded depth of up to 70 meters.
Another tree that has incredibly deep roots is the Wild Fig that was discovered near Ohrigstad, in the Echo Caves. This tree’s roots sank to a depth of over 121 meters.
Other trees that have deep and strong roots include hickories, white oaks, Japanese Pagoda, Sweetgum, Black gum, hornbeam cultivars, and walnuts.
Are most tree roots as long as the tree is tall?
No, tree roots are not as long as the tree is tall. Most tree roots, irrespective of height, grow within 60 cm of the soil’s surface. In most cases, the depth of the growth depends more on the species of the tree (drought tolerant trees are deeper rooted) and soil conditions in which the tree is growing. Therefore, factors like soil compaction matter more than the tree’s height.
Do tall trees have deep root systems?
No, tall trees do not necessarily have deep roots. This is because a tree’s height has nothing to do with the depth of its root system.
What factors influence tree root growth?
The following are factors that play a significant role in determining how roots grow.
Spacing
If trees are planted close together, they are likely to have roots that are less extensive. This is because of competition from neighboring trees.
Soil structure
A tree that grows on soil whose bedrock is nearer the surface is likely to develop shallow roots. It is more likely to have wider roots as it searches for nutrients — as a way of making up for the lack of depth.
Soil compaction
Roots have a harder time growing through compacted soils. As a result, most trees that grow in such soils tend to have thicker roots. The roots also tend to be fewer in number.
Location of moisture
Tree roots are ruthlessly opportunistic. If there is a moisture source, they will grow towards it. As a result, they are likely to grow towards burst pipes. And are more likely to avoid dry areas like the foundations of homes.
Barrier presence
If there is a barrier near a tree, it will restrict growth. Some of these barriers include artificial root barriers, buildings, rocks, and walls.
What are the benefits of knowing how tree roots tend to grow?
Why should you care about the depth or the length of tree roots on your property?
Here is what you need to know.
It helps to prevent foundation damage
A tree, especially one with an aggressive root system, has to be planted at a safe distance away from a house. Planting it too close to a house could lead to extensive damage.
If you know how far the root spread of a given species is, you can easily figure out an ideal planting distance. This can go a long way towards reducing the instances of tree roots growing under your home and facing premature foundation problems.
It helps with zeroing in on the perfect gardening spots
An invasion of tree root systems is not good for your garden. This is because the roots will rob your plants of nutrients and moisture. This can lead to poor plant health and yields.
When you know how far a given tree’s roots can grow, you can determine the safest distance to install a garden. You can also figure out whether installing a root barrier is necessary.
This knowledge will help to simplify the process of finding the perfect spot for your plants.
It helps with planning construction or installation work
Roots are essential to a tree’s survival. The slightest root injury can end up compromising a tree’s health. In some cases, it can lead to death.
Therefore, when carrying out any construction or installation work, it is always a good idea to know how far tree roots stretch. This is something that can help to reduce the odds of accidentally killing the trees on your property.
It is critical to maximizing tree health
Knowing how long and how deep tree roots spread can come in handy in helping you figure out how to maximize tree health.
This knowledge will be useful in determining the ideal spacing of given trees. This is something that will definitely reduce competition for resources among trees — something that will go a long way toward guaranteeing better tree health.
What trees have no invasive roots?
Trees that have invasive roots2 can be a nightmare. They can damage your home’s foundation, destroy your plumbing system, and even starve other plants in your garden.
Therefore, if you are planning on planting a tree near your home or next to your garden, opting for a tree with non-invasive roots is the best solution.
Here is a list of popular tree species that have non-invasive roots.
- Dwarf Korean lilac
- Eastern redbud
- Japanese maple
- Crape myrtle
- Cornelian cherry dogwood
- Adams crabapple
- Boxwoods
- Glossy abelia
- Hollywood juniper
- Chinese pistache
- Trident maple
- Amur maple
- Dwarf orange tree
- Avocado tree
How do you control tree root growth?
Tree roots can become a nuisance. They can also become destructive. Whichever the case, knowing how to control their growth can be a lifesaver.
The following are the different ways through which you can get the growth of tree roots under control.
Root barrier installation
Root barriers work by creating a surface through which roots can’t get through. They effectively deflect the growth of the roots downwards and away from areas that you want to shield from root invasion.
Cutting
If the roots are already too invasive, you can simply cut them off.
However, when doing so, you need to exercise the utmost care as some tree species are highly sensitive to root interference. Cutting off even the tiniest portion of their roots can end up killing them.
As a result, cutting tree roots is a control technique that should be used by qualified tree experts. And if not, you should at least use it only when you are under the guidance of one.
Tree removal
If a tree’s root system is highly invasive, and the headache of dealing with its roots is not worth the benefit that the tree provides, then removing the tree is a good idea. You can then replace it with a tree that has non-invasive roots.
FAQ's
Yes, tree roots usually keep growing provided there is a need for more nutrients and water. This growth is usually geared towards maximizing the surface area of the roots. And it is all intended to ensure that the tree has enough resources to not only survive but also thrive.
Trees whose primary roots tend to grow straight down are the ones that have the taproot system. Trees like silver fir, Scots pine, and English oak are great examples of trees that grow deep taproots.
A tree with a surface root system is one whose roots usually grow laterally and horizontally. The tree’s root system tends to remain just below the surface.
White pines, Norway spruce, aspens, and ash trees are good examples of trees with such root systems.
No, tall trees do not necessarily have a better root system. If they have wider canopies, they may have wider root systems. But a tree’s height has no bearing on how good a root system the tree has.
Generally, a tree can survive when 25% or less of its roots are damaged. Therefore, provided the damage or cutting affects less than 1/4 of the tree’s total tree root zone, there is a good chance that the tree will survive.
- Leda Marritz , (2012) How Deep Do Tree Roots Really Grow? <https://www.deeproot.com/blog/blog-entries/how-deep-do-tree-roots-really-grow/> Accessed: 22-02-2024
- RootWell, (2021) Trees With The Strongest and Deepest Roots <https://www.rootwell.com/blogs/tree-roots-strongest-and-deepest> Accessed: 22-02-2024
