How many roots does a tree have


3 Types of Tree Root Systems

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We’re familiar with what a tree looks like aboveground, but the underground part of a tree is just as important. The roots are often the “root” of tree health, failure, and longevity. Urban tree roots are highly influenced by the urban environment, which often consists of compacted, small soil volumes. But tree roots can also be partially determined by genetics. Understanding the 3 types of root systems trees have can help you take care of your tree or select the best tree for your property!

Tree Roots

Before we dive into root systems, it helps to know the 5 basic types of tree roots and their function. These are the most common root types in temperate climate trees.

  1. Tap roots: Every tree starts with a tap root that provides stability and absorption. Over time, other roots outgrow the taproot. Most taproots don’t continue to grow ever more deeply because deep soils lack the oxygen and nutrients that roots need to survive.
  2. Lateral roots: Lateral roots grow outwards right under the soil surface. They absorb a lot of water and nutrients as well as anchoring the tree.
  3. Oblique/heart roots: Oblique roots, also known as heart roots, grow at a diagonal and have the same function as lateral roots.
  4. Sinker roots: Sinker roots grow downwards from the lateral roots to a depth of several feet. There, lateral roots take advantage of any water and nutrients deeper in the soil in addition to increasing tree stability.
  5. Fine roots: All the root types aforesaid can give rise to fine roots, which is where water and nutrients are directly absorbed. They also house mycorrhizae, which are fungal partnerships that increase root absorption capacity.

 

3 Types of Root Systems

Each root system below is defined or dominated by one root type, hence their names. Some tree species are more likely to have one root system than another, but keep in mind that site conditions are just as important. Most urban trees have lateral root systems due to shallow topsoil layers and frequent, shallow irrigation.

Taproot System

Dominated By: Tap root.

Stability: Tap root systems are very stable, but extremely rare in mature trees.

Common Species: Some oaks and pines, hickory, sweet gum, tupelo, walnut.

 

Lateral Root System

Dominated By: Lateral roots.

Stability: Lateral root systems obtain their stability from tree weight and root spread. These root systems don’t necessarily have a lot of root mass, but because the roots are so widespread, the tree can be supported without investing so much in roots. About 80% of tree species and most urban trees have lateral root systems.

Common Species: Ash, birch, cottonwood, hackberry, maple.

 

Heart (aka Oblique) Root System

Dominated By: Heart (aka oblique) roots.

Stability: Heart root systems obtain their stability from root ball weight and soil resistance. The tree is held up by the weight of its root ball counteracting the weight of its aboveground parts and the strength of the soil around it. Heart root systems are prone to failure in wet soils. Once the soil is wet, wind and gravity can make the tree rotate in the ground, much like a ball-and-socket joint.

Common Species: Honey locust, red oak, sycamore. More common in Mediterranean and arid climates.

Sophia Huang2021-09-23T19:44:06+00:00

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How Deep Do Tree Roots Really Grow?

Our 2010 blog entry by James Urban, FASLA, on the topic of how deep tree roots grow is consistently one of our most popular. Obviously there is a curiosity about this topic and a need for useful data about it. But the original post is a little technical and not as image-heavy as we’d like. So today we’re bringing you a new and improved version of the original post, with additional pictures and more simplified explanation of the factors that really influence how deep tree roots grow. 

How deep tree roots grow depends on three simple factors. To answer this question I contacted Jim Urban, FASLA, a noted tree and soil expert. He contributed to the following post.

Roots require three things: water, oxygen, and soil compaction levels low enough (or with void spaces sufficiently large enough) to allow root penetration. If all these conditions are met, roots can grow to great depths. Under ideal soil and moisture conditions, roots have been observed to grow to more than 20 feet (6 meters) deep. 

Early studies of tree roots from the 1930s, often working in easy-to-dig loess soils, presented an image of trees with deep roots and root architecture that mimicked the structure of the top of the tree. The idea of a deeply-rooted tree became embedded as the typical root system for all trees. Later work on urban trees that were planted in more compacted soils more often found very shallow, horizontal root systems. Urban foresters have successfully spent a lot of energy trying to make people understand that tree roots have a basically horizontal orientation, to the point that even many tree professionals now believe that deep roots in trees are a myth. The truth lies somewhere in between deep roots and shallow roots.

This totally horizontal root system formed on top of poorly drained soils. Photo courtesy of Miles Barnard.

Simply put, by Jim: “Trees are genetically capable of growing deep roots, but root architecture is strongly influenced by soil and climate conditions.”

The most typical limitations to tree rooting in urban areas are soil compaction and poor drainage. These are often related, with a compaction layer creating a poorly-draining hard pan. This results in a perched water layer that restricts roots. Hard pans and perched water tables can also be found in nature. In fine-grained clay soils and fine-grained silty soils, pore space — and therefore and rooting depth — is often limited. Since these conditions are quite common in urban areas, shallow rooted trees are often seen as “typical.”

Six foot long sinker or striker roots in well-draining soils. Note the remnant of horizontal roots at the trunk flare. Photo courtesy of Miles Barnard.

Orjan Stahl, a tree researcher in Stockholm, made an exhaustive study of over 500 trees that had root and utility conflicts. He regularly found roots at depths of 7 to 9 feet (2.1 to 2.7 meters) and the deepest root he encountered was at 23 feet (7 meters). In their 1991 paper, “On The Maximum Extent of Tree Roots,” E.L. Stone and P.J. Kalicz summarized previous root depth studies of 49 genera and 211 species growing in a wide variety of soil types. They found numerous examples of trees reported to be growing roots to over 33 feet (10 meters), and one report of a tree that grew roots to a depth of 174 feet (53 meters). Clearly, a tree’s ability to grow deep roots is not a significantly limiting factor in soil design.

4 foot deep rooting in loam soil that was on top of a hard pan. Photo courtesy of James Urban.

Given all this, and the unpredictable site constraints of the urban environment, urban trees need flexible solutions that can enable roots to grow out or down. In some sites, increasing soil depth is not a problem, while expanding may be limited by other constraints. The opposite can also be true. This is why the Silva Cell system is flexible in all three dimensions to respond to different spatial limitations.

These roots go at least 4 feet deep. This tree fell over after the irrigation contractor installed a line on the up wind side. Photo courtesy of James Urban.

The designed maximum depth of the system is 45 inches (1150mm). This is a strategic compromise between the system’s structural requirements, soil volume, and cost and constructability issues. The Silva Cell was designed to provide a deep soil volume because roots will grow to these depths. For urban sites where deep excavation is limited, one- or two-layer systems can provide the same total soil volume across a shallower profile.

Two other factors are absolutely critical to the ability of roots to grow though the entire soil profile: the type of soil that is used, and designing the system to permit adequate water into and to drain out of the soil. These features must be designed to reflect the environment in which the Silva Cells are to be placed, the types of soil resources available and the project performance expectations of trees, soil and water.

Horizontal rooting to about 4 foot depth in loam soil over river wash till. Photo courtesy of James Urban.

How many meters do tree roots drop?

Tree roots are a true masterpiece of nature. From the first moment the seeds germinate, they go in search of much-needed water to keep the plant alive. Water containing minerals needed for growth. But not only that, but also, thanks to the rod, which is the thickest of all, is well fixed on the floor. Thus, no matter how strong the wind blows, it will be difficult to start it.

Although they also have a disadvantage, and this is that in the incessant search for water, depending on the type, it can damage pipes or any structure. To avoid this, I will tell you how many meters the roots of trees descend .

Index

  • 1 What are tree roots?
  • 2 How many meters do they go down?
  • 3 Deep tap root trees
    • 3.1 Genus Ficus
    • 3.2 Genus Pinus
    • 3.3 Genus Eucalyptus
  • 4 Non-invasive rooted trees
    • 4.1 Genus Citrus
    • 4.2 Genus Lagerstroemia
    • 4.3 Genus Cercis

What are the roots of the trees?

Before moving on to the topic, it is important to first talk a little about the features of the root system of trees, as this will help you avoid problems. What you need to know is that the roots, from the moment the seeds germinate until almost the end of the plant's life, form a network in search of water.

This network initially has a distinct primary or main root, which is the so-called rotation, which is responsible for anchoring the trees to the ground, but as the trees grow, the roots become mostly superficial, and only a few of them continue to grow vertically. In fact, if we take a mature tree about 50 years old as an example, we can be sure that about 90% of the roots are in the first 50 centimeters of the ground. . But that's not all.

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And the fact is that the size of the entire root system of a tree tends to match (more or less) the size of its crown, which makes sense if we think that all these branches should receive the water that their roots receive. in most cases from the ground to produce leaves, flowers, fruits and seeds. This means that if we have a tree with a crown about 2 meters in diameter by 3 meters at the highest point, its roots will take up about 2 meters in diameter (in this case, the depth is not taken into account because it is difficult to go down a meter and more).

How many meters do they descend?

How deep the roots go depends on several things: soil type , plant species in question and the amount of water in the ground . As a rule, the wetter the soil, the longer its root system will be.

However, You should know that the vast majority of trees, namely 80% of them, as well as the vast majority of their roots, only go down to 60 cm. . From there, they lay out their roots horizontally. The roots of the remaining 20% ​​can penetrate more than 2 m underground, so they will have to be planted away from any buildings.

Deep-rooted trees

Since you are probably wondering what these deep-rooted trees are, we couldn't end this article without mentioning the most important ones:

Genus Ficus

Image - Wikimedia / Forest and Kim Starr

Ficus are trees, shrubs or vines native to the intertropical zone of the world. Many species are used as house or garden plants, such as Ficus pumila , Ficus Benjamina o el Ficus robusta . Its height is variable, but can easily exceed 's 10 meters, and its roots extend several meters in all directions.

Genus Pinus

Image - Flickr / CARLOS VELAZCO

Pine (or pine) are woody or shrubby coniferous trees with a crown, usually pyramidal, and sometimes wide and round, which they can reach 30 meters . The best known and most commonly used types are Pinus Pinea , Pinus halepensis or common .

Genus Eucalyptus

Eucalyptus (eucalyptus) - trees, especially growing in Australia and New Guinea. It has a fast growth and they can measure over 60 meters. . Its roots are not only unsuitable for growing in a small garden, but also prevent other plants from growing around them. Interesting species for very large plots are, for example, Eucalyptus deglupta for tropical climates or Eucalyptus camaldulensis .

Non-Invasive Root Trees

If you are looking for plants with a more shallow and non-invasive root system, I recommend more plants in these genera: 5 to 15 meters . They are native to tropical and subtropical Asia and there are many species that produce delicious fruits such as Citrus reticulata (mandarin), Citrus x Paradisi (grapefruit) or Citrus x sinensis (orange tree).

Genus Lagerstroemia

Image - Flickr / Joel Abroad

Lagerstroemia are trees and shrubs native to tropical regions of Asia. They can grow up to 10 meters. , and produce many purple or white flowers. The most famous species is Lagerstromia , popularly called the tree of Jupiter.

Genus Cercis

Image - Wikimedia / Batsv

Cerci are deciduous trees native to Europe, Asia and North America. They reach a small height, from 6 to 10 meters. , with a wide crown that fills with pink flowers in spring, like European purple o el Chinese purple .

Do you know other trees that are not invasive?


How many meters do tree roots drop?

Tree roots are a true masterpiece of nature. From the first moment the seeds germinate, they go in search of much-needed water to keep the plant alive. Water containing minerals needed for growth. But not only that, but also, thanks to the rod, which is the thickest of all, is well fixed on the floor. Thus, no matter how strong the wind blows, it will be difficult to start it.

Although they also have a disadvantage, and this is that in the incessant search for water, depending on the type, it can damage pipes or any structure. To avoid this, I will tell you

Before moving on to the topic, it is important to first talk a little about the features of the root system of trees, as this will help you avoid problems. What you need to know is that the roots, from the moment the seeds germinate until almost the end of the plant's life, form a network in search of water.

This network initially has a distinct primary or main root, which is the so-called rotation, which is responsible for anchoring the trees to the ground, but as the trees grow, the roots become mostly superficial, and only a few of them continue to grow vertically. In fact, If we take as an example a mature tree about 50 years old, we can be sure that about 90% of the roots are in the first 50 centimeters of the ground. . But that's not all.

Subscribe to our Youtube channel

And the fact is that the size of the entire root system of a tree tends to match (more or less) the size of its crown, which makes sense if we think that all these branches should receive the water that their roots receive. in most cases from the ground to produce leaves, flowers, fruits and seeds. This means that if we have a tree with a crown about 2 meters in diameter by 3 meters at the highest point, its roots will take up about 2 meters in diameter (in this case, the depth is not taken into account because it is difficult to go down a meter and more).

How many meters do they descend?

How deep the roots go depends on several things: soil type , plant species in question and the amount of water in the ground . As a rule, the wetter the soil, the longer its root system will be.

However, You should know that the vast majority of trees, namely 80% of them, as well as the vast majority of their roots, only go down to 60 cm. . From there, they lay out their roots horizontally. The roots of the remaining 20% ​​can penetrate more than 2 m underground, so they will have to be planted away from any buildings.

Deep-rooted trees

Since you are probably wondering what these deep-rooted trees are, we couldn't end this article without mentioning the most important ones:

Genus Ficus

Image - Wikimedia / Forest and Kim Starr

Ficus are trees, shrubs or vines native to the intertropical zone of the world. Many species are used as house or garden plants, such as Ficus pumila , Ficus Benjamina o el Ficus robusta . Its height is variable, but can easily exceed 's 10 meters, and its roots extend several meters in all directions.

Genus Pinus

Image - Flickr / CARLOS VELAZCO

Pine (or pine) are woody or shrubby coniferous trees with a crown, usually pyramidal, and sometimes wide and round, which they can reach 30 meters . The best known and most commonly used types are Pinus Pinea , Pinus halepensis or common .

Genus Eucalyptus

Eucalyptus (eucalyptus) - trees, especially growing in Australia and New Guinea. It has a fast growth and they can measure over 60 meters. . Its roots are not only unsuitable for growing in a small garden, but also prevent other plants from growing around them. Interesting species for very large plots are, for example, Eucalyptus deglupta for tropical climates or Eucalyptus camaldulensis .


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