- In the Garden
- Colorado State University
- Quick Facts…
- Where Roots Grow
- Why Roots Grow Where They Do
- Causes of Root Injury and Disease
- Types of Root Diseases
- Root Disease Signs and Symptoms
- Control and Prevention
- Want more gardening info?We’ve got it – in spades!
- What To Do About Exposed Tree Roots
- What Not To Do
- What To Do Instead
- Can I Cover Tree Roots With Soil?
- The Best Way to Cover Your Exposed Tree Roots
- Choosing the Best Way to Cover Exposed Tree Roots
In the Garden
Q: Tree roots have come up to the surface in our lawn. It’s so bad the lawnmower blade hits them. What is causing this, and what is the best way to deal with them without harming the tree?
A: There are several reasons tree roots come up to the surface. Although some kinds of trees, such as poplars and ornamental cherries, are prone to produce surface roots, usually they’re a sign of poor soil conditions. Heavy clay or compacted soils lack the air and moisture necessary for proper root growth below ground, so roots are forced to come up to the surface to find what they need for survival.
Unfortunately, as the tree grows, surface roots also increase in size, and if they are on a lawn they can become so large they can make mowing difficult, if not impossible.
Covering surface roots with soil won’t solve the problem. Adding too much soil at one time can suffocate tree roots, while adding a bit at a time is pointless because the soil simply dissipates and disappears into the lawn.
If necessary, surface roots can be removed, but it must be done properly or it could harm the tree. During the dormant season, remove only one large root or two smaller ones per year. Allow at least 10 inches of distance from the trunk for every inch of the diameter at ground level before making the cut.
To prevent the likelihood of disease problems, first dig a trench around and under the root; then use a clean, sharp lopper, or in the case of very large roots, a pruning saw to make a clean cut. Finally, do not apply pruning paint. If all goes well, new roots will form and grow from the cut end.
Of course, the best longterm solution is to remove the lawn where the surface roots are causing a problem and turn the area into a garden bed. You’ll have a wonderful new garden space to enjoy and you won’t be forced to spend hours of backbreaking work every dormant season removing roots and/or replacing broken mower blades.
Q: Twenty years ago, I built a treehouse for my children. It is still there, suspended by 1-inch rope between four fir trees that are clustered together. I am going to take it down but the rope has become buried deep in the bark of the growing trees. Do I pull it out or leave it and just let the tree envelop it?
A: This situation illustrates why we shouldn’t wrap anything tightly around the trunk or branches of a tree. As the tree grows and increases in girth, if wire or rope is left in place encircling a branch, over time it will cut into the tree, causing a condition known as girdling.
Girdling can harm a tree in two ways. First, it blocks nutrients from moving past the constriction, preventing carbohydrates from reaching the roots. If the girdling occurs on a main trunk, it can lead to stunted root growth and endanger the stability of the tree. If girdling is severe, you will notice a large bulge made up of blocked nutrients above the restriction.
The second problem is that if the tree grows around and envelops the encircling material, it can create a weak spot where the tree could break in a windstorm or a heavy snow.
If the rope can be removed without seriously harming the bark, the damage is minimal and you probably don’t have to worry about it. If the rope is enveloped and can’t be easily removed from a trunk or major limb, and the tree is located where falling branches could cause harm, call in a certified arborist to assess your tree.
Much to the dismay of homeowners, landscape trees sometimes grow roots on top of the surface of the lawn or possibly even buckle sidewalks and driveways. These surface roots can be quite a nuisance to lawn mowers and human feet.
There are several reasons why the roots come to the surface. Some tree species are more prone to surface roots than others, most notably silver maple, poplar and willow. But almost any large, older tree can produce some surface roots.
Although trees do send some roots down deep for moisture and stability, most tree roots tend to grow much more shallowly than most people think – usually only 4-8 inches deep. Just as the trunk of the tree grows in girth with age, so do the roots. So over time, some of the shallow, older roots of the tree will naturally enlarge to the surface. Sometimes, roots become visible due to erosion of the surface soil. Compacted, poorly drained soil will also lead to more shallow root development.
Pruning off the visible roots is likely to cause serious damage to the tree over time and should only be used as a last resort to spare sidewalks and driveways where relocating the pavement is not feasible.
The best prevention for surface roots is to select appropriate plants for the situation such as shorter tree species and planting at least 4 feet away from paved areas. But if you already have an older large tree with surfacing roots, you can adapt your landscaping maintenance to help avoid troubles.
A temporary solution to surface roots is to apply a shallow, 1 – 2 inch layer of good-quality soil mix and then replant the grass. However, it won’t be long before tree roots will reappear as they continue to grow in girth.
A more permanent solution would be to replant the affected surface area with a taller ground-cover type plant that will not need mowing, being careful to avoid injury to the major tree roots at planting. Or, better yet, replace the turf with organic mulch such as shredded or chipped hardwood bark.
Root barriers made of metal, plastic or fabric have been tried with some degree of success in slowing the development of surface roots. However, over time, most root barriers will fail, either through cracking of the material or roots growing under or over the barrier into decorative top mulch.
Colorado State University
by J.M. Sillick and W.R. Jacobi * (12/13)
Figure 1: Area root distribution vs. crown distribution.
- Most tree roots are located in the top 6 to 24 inches of the soil and occupy an area two to four times the diameter of the tree crown.
- Roots obtain water, oxygen nd minerals from soil. They do not grow toward anything or in any particular direction.
- Soil compaction, change in soil depth and improper watering can injure roots, increasing stress and susceptibility to disease and insects.
- To avoid root disease, maintain a healthy, vigorous environment around a tree. Once a root system is severely affected, the tree usually must be removed.
The root system of a tree performs many vital functions. In winter, it is a store-house for essential food reserves needed by the tree to produce spring foliage. Roots absorb and transport water and minerals from the soil to the rest of the tree. Roots also anchor the portion of the tree above ground. It is important to keep the portion above ground healthy to ensure an adequate food supply for the roots to continue their important functions.
Where Roots Grow
Figure 2: Tree wells cannot compensate for the addition of soil over tree roots.
Tree root systems consist of large perennial roots and smaller, short-lived feeder roots. The large, woody tree roots and their primary branches increase in size and grow horizontally. They are predominantly located in the top 6 to 24 inches of the soil and occasionally can grow deeper 3 to 7 feet if soil conditions allow. Root functions include water and mineral conduction, food and water storage, and anchorage.
In contrast, feeder roots, although averaging only 1/16 inch in diameter, constitute the major portion of the root system’s surface area. These smaller roots grow outward and predominantly upward from the large roots near the soil surface, where minerals, water and oxygen are relatively abundant. The major function of feeder roots is the absorption of water and minerals. Under normal conditions, feeder roots die and are replaced on a regular basis.
Large roots and small feeder roots occupy a large area under ground. Typically, the root system of a tree extends outward past the dripline, two to four times the diameter of the average tree’s crown (Figure 1).
Figure 3: Root destruction, soil removal and soil compaction from construction equipment.
Figure 4: Trenching can severely injure a tree. Instead, auger under roots.
Why Roots Grow Where They Do
Roots grow where water, minerals and oxygen are found in the soil and allow root growth. Roots need some water and oxygen but if soils are saturated with water, most roots will die. Because oxygen is usually located in the upper surface layer of soil, the largest concentration of feeder roots exists in this zone.
Other factors that determine root growth include soil compaction (reduction in air pockets resulting from soil particles being packed together) and soil temperature. In general, as the depth increases, soil compaction increases, while the availability of minerals, oxygen and soil temperature all decrease. In some instances, hard, compacted soil (hardpans) can occur near the surface, which restricts root growth.
Causes of Root Injury and Disease
There are many ways to injure tree roots and stress trees. Some injuries are unintentional and cannot be avoided. However, most root damage can be avoided with some care.
One of the biggest killers of urban trees is use of heavy clay subsoils instead of topsoil and soil compaction. Heavy clays and soil compaction restricts water and oxygen uptake by roots, and is associated with use of deep sub soils as fill for landscaping and compaction from construction of roads, parking lots, and from foot traffic, construction machinery, livestock, poor soil preparation, and a host of other factors.
Changes in soil depth around trees can also cause injury to root systems. The addition of only 4 to 6 inches of soil over an existing root system drastically reduces the amount of oxygen and water available to the roots (Figure 2). The opposite issue of removal of soil around an existing tree can expose and injure roots, change the soil conditions where roots grow, and reduce water availability (Figure 3).
Other causes of root problems include over- and underwatering, improper fertilization, and competition between roots. Overwatering causes the soil pore (air) spaces to fill with water and restrict oxygen uptake. Underwatering does not provide sufficient water for proper root development. Overfertilization can injure or kill the roots, while underfertilization results in a lack of the minerals essential to maintain a healthy tree. Competition for water and minerals between tree roots, bushes, grass and flowers can also stress trees. Trees can be stressed from root damage by routine soil preparation in the tree’s root zone for flower planting.
Other practices that increase root injury and disease susceptibility are: improper use of herbicides, deicing salts and other chemicals; wounding through digging and trenching (Figure 4); and adding deep mulch (over 6 inches), plastic or pavement that restricts or suffocates roots. After a tree is established, anything that changes the soil condition or the oxygen and water supply can be extremely detrimental.
Types of Root Diseases
The two basic types of fungi that cause root diseases are those that kill feeder roots and those that cause decay in the large, woody roots. Many fungi occur on small feeder roots. The more common organisms are species of Phytophthora, Pythium and Fusarium. These break down the feeder roots and reduce the tree’s mineral- and water-absorbing capability. Fungi that attack large, woody roots suppress growth, decay food-transporting cells, reduce food storage and reduce structural support for the tree.
Root Disease Signs and Symptoms
Figure 5: Yellow, chlorotic foliage from root disease.
Typical symptoms associated with root diseases often are confused with mineral deficiencies because high numbers of dead roots reduce water and mineral uptake. Symptoms of root disease include small, yellow, chlorotic foliage (Figure 5); reduced growth; scorch; tufted leaves at the end of branches; and branch dieback. Fungal fruiting bodies (mushrooms or conks) at the base of the tree, as well as white fungal growth under the bark, also indicate root disease. Symptoms of root problems from construction damage or other detrimental activities may appear one to several years after the damage occurred.
Direct examination can verify a disease. Carefully excavate roots by removing a small patch of the bark. A brown coloration beneath the bark indicates a dead root, while a healthy root usually appears white or light-colored (Figure 6).
Control and Prevention
The most effective way to reduce the possibility of root injury and disease is to keep the tree healthy and vigorous. A healthy root environment consists of adequate growing space for the root system, well-conditioned soil 16 inches to 24 inches deep, and sufficient water and oxygen. To check the water and soil condition of the root environment, dig a hole outside the dripline of the tree and determine if the soil is dry, wet or compacted. If you can’t get the shovel in the ground, the soil is dry. Soil moisture is adequate if the soil can be madeinto a ball with little pressure. Long, deep watering over the entire root system with time for the soil to dry between watering is better for trees than frequent light watering. Watering once a month during a long, dry winter also is helpful.
Avoid any practice that injures the roots. This includes: soil compaction, soil depth changes, mechanical injury, and improper watering and fertilization techniques. However, if these practices cannot be avoided, try to minimize damage.
To minimize soil compaction, remove compacted soil and replace it with noncompacted soil. Provide adequate drainage before planting. Use 2 to 3 inches of organic mulch (peat moss, wood chips, tree bark) around the base of a tree to improve soil aeration and water availability. Adding new mulch every three years or so will be needed as the mulch decays and improves the soil structure.
Avoid fertilization damage by applying nitrogen fertilizer to established trees immediately after spring leaf expansion, not in the late summer and fall.
Once a tree is infected, it is difficult to control a root disease. If only a few roots are infected, try to restore the tree’s health or at least delay disease progression. Since the fungus probably entered the tree due to some stress or injury, eliminate the stress and restore the tree’s vigor by proper amount of water year round.
If the root system is severely damaged, tree removal is usually recommended. A tree with a structurally weakened root system can fall over during wind storms. Before replanting in the same area following death, remove as much of the dead stump as possible.
Want more gardening info?
We’ve got it – in spades!
Whether you’re a newcomer to Colorado gardening or an old hand at it, you’re sure to find just what you need at The University Resource Center.
Our publications deal with questions specific to Colorado gardening: plants for mountain communities, xeriscaping, fruit and vegetable varieties, insects and weeds, soil and fertilizer.
From fruits and vegetables to nourish your body to flowers to nourish your soul, we can help.
Address: The University Resource Center
115 General Services Bldg.
Colorado State University
Fort Collins, CO 80523-4061
Phone: (970) 491-6198
Toll-free: (877) 692-9358
Fax: (970) 491-2961
E-mail: [email protected]
For more information, see these fact sheets from Colorado State University Extension:
- Colorado Master Gardener Garden Notes #616 – Pruning Mature Shade Trees.
- 7.214, Mulches for Home Grounds.
- Colorado Master Gardener Garden Notes #711 – Vegetable Garden: Soil Management and Fertilization
- Colorado Master Gardener Garden Notes #633, The Science of Planting Trees.
- 7.418, Small Deciduous Trees.
- 7.419, Large Deciduous Trees.
Fact sheets are available online at: http://extension.colostate.edu/publications-2/
Colorado State University, U.S. Department of Agriculture and Colorado counties cooperating. Extension programs are available to all without discrimination. No endorsement of products mentioned is intended nor is criticism implied of products not mentioned.
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What To Do About Exposed Tree Roots
Every year we get a few calls about tree roots in people’s lawns. They cause problems for mowers, they’re trip hazards for kids, and they’re just kind of ugly. The question is, what, if anything, can you do about them?
The first thing to understand is what causes the exposed roots. It’s not that the tree root is bursting out of the ground like some kind of tentacle. Tree roots are not motile. Some trees, like maple, have extremely shallow roots.
If a tree root is exposed to the air, it’s generally because the soil left. And why did the soil erode from around the tree root? Well, typically, it’s because there was nothing holding it there.
We’re all familiar with the problem of grass dying under trees. Not only do they not get enough sunlight, they’re also competing with the tree roots for water. On a hot summer day, a mature oak will absorb up to 100 gallons of water. That’s a powerful thirst.
What Not To Do
When you realize that the exposed roots are caused by erosion, your first instinct will probably be to add topsoil and cover them back up. But not so fast — unless you can get the grass to grow back nice and thick, in a couple of years you’ll be right back where you started, swearing every time you whack the mower blade on them.
Some people will go a step further and create a big bed around the trunk of a tree, maybe plant it full of shade-loving hostas and add a garden bench. But the problem with that is that you’re depriving your tree of water. A good percentage of the rain that falls on trees gets channeled down the trunk. The rest falls on the drip line (part of the reason why tree roots extend as far as they do.) If you plant a perennial bed under your tree, you may have just halved the amount of water it receives. Will it be able to survive on that? Who knows? Do you really want to find out?
What To Do Instead
You’re going to love how simple this solution is. It’s the least work of anything mentioned so far.
Mow down whatever grass is growing under the tree. Raze it to the ground with a weed-whipper. You want bare dirt.
Then, add 1-3 inches of bark mulch. You can use the double-shredded kind if you want, just remember it absorbs more water. Bark mulch will let it all flow through to the roots.
How big a circle of mulch do you want under your tree? Anywhere from half to two-thirds of the total area of the drip-line. Get too close to the edge where it gets more sun and you’ll get a lot more weeds in your mulch.
What’s not to love about this solution to exposed tree roots? It’s less mowing for you, and your yard looks even more put-together and professional.
Can I Cover Tree Roots With Soil?
Live oak with Spanish moss. Photo by Ralph Anderson.
Question from Desperate Reader: I have a 40 year-old live oak with unsightly, exposed roots on the soil surface. We’re afraid someone may trip. Can we make a flower bed over the roots?
Grumpy’s Totally Correct Answer: Trees in general do not like having soil piled over the roots. The roots need to “breathe” — a deep layer of soil smothers them. Some trees, like pines, are less sensitive to this, but oaks a very sensitive. Pile any soil at all atop the roots and pretty soon, the trees will die. So no flower garden.
Your situation isn’t hopeless, however. What you need to do is cover the roots with material that doesn’t compact like soil and prevent oxygen from reaching the roots. Therefore, you could fill between the roots with several inches of coarse gravel, river stones, pine straw, or shredded bark.
Grumpy’s on Vacay!
Image zoom emIsle of Santorini. Photo by HBarrison./em
That’s right! For the next couple of weeks, Grumpy will be cruising to exotic locales all over the known world as he seeks to recharge his gardening batteries. He will not be able to check email during this time, so either wait until October 29 to post a gardening question or wait patiently for an answer.
Don’t think Grumpy has abandoned you. In the time I’m away, I will be answering a gardening question sent in by a faithful reader right here every Tuesday, Thursday, and Sunday.
Now could I please have another glass of red?
Next Post: Preparing the Soil for Next Spring
Ultimate ways to cover exposed tree roots on June 9, 2017 in Tree Care Advice
Every year AAA Tree Experts Inc. receives calls to get rid of exposed tree roots, without damaging the tree. Above the ground tree roots usually, spoil the aesthetic value of the outdoor landscape. They also are a hindrance while mowing the lawn, the trip of these roots can hurt kids and adults if they go unnoticed. Hence, home and property owners are concerned about these exposed tree roots. On the other hand, all of us enjoy the joy of watching healthy tall trees all around. But to be honest, the sprawling exposed roots are not a pleasing sight for the eyes. Pruning or cutting these roots can make the tree weak and unhealthy.
Covering these exposed tree roots is arguably the best way to deal with exposed tree roots.
Here is how it goes-
Flowers or Grass
Planting your favorite turf or flowers has the potential to add color and beauty beneath the huge tree. The tree’s green canopy will protect these delicate plants from excessive sunlight and make your lawn look beautiful. These roots also take up excess water that is not needed by the smaller plants, planted underneath the trees to grow.
To camouflage the roots with the ground, adding topsoil is an easy and pocket-friendly option. But this choice comes with a disclaimer, as the use of an incorrect type of topsoil or too much soil will risk the trees process to stay hydrated. A topsoil is just an option available to quickly fix the issue of exposed tree roots.
Concrete sounds very conventional and pocket-friendly. But building a concrete structure by creating a stepping pathway may sound like an incredible idea. This option certainly needs to be thought over again, as concrete has high chances of blocking tree roots from receiving the required amount of oxygen and water.
Mulch it up
Based on your needs, mulching can be a great alternative to protect exposed tree roots. 2 to 3 inches of well-added mulch can give your lawn that clean and crisp look. Mulch will also help keep the roots moisturized and protected.
Depending on your requirement, any one of the above methods can be applied in order to make your lawn free from above the ground roots. In case, you are still confused and don’t know where to begin, pick up your phone and call for professional tree care services for a perfect process to cover exposed tree roots.
The Best Way to Cover Your Exposed Tree Roots
We love seeing our trees grow tall and wide, but their sprawling roots are harder to adore. Often unsightly, they can also be an obstacle and make lawn care a hassle.
In short, above-ground tree roots are a pain. Chances are you’ve thought about removing the roots altogether. Bad news, though. Pruning these roots often makes the tree unstable or unhealthy–and if done wrong, can kill the tree. So now what? Instead of cutting exposed tree roots, try covering them.
Browse this list to find the perfect way to cover your tree roots above ground.
Choosing the Best Way to Cover Exposed Tree Roots
Can you put grass or flowers over exposed tree roots?
While you can go this route, you may run into issues down the road. Ever wonder why grass or flowers under your tree die so fast? It’s because the tree’s shady canopy blocks other plants from getting enough sunlight. Plus, the tree roots take most of the water in the soil for themselves.
If you can find a grass or flower that thrives in the shade and needs little water, this may work. But it will be tricky!
Is it okay to add topsoil over tree roots growing above ground?
Adding topsoil over tree roots presents some problems, too. If you use the wrong soil or pack on too much, the tree won’t get enough water to stay hydrated. Plus, the roots will likely grow through the soil you just added before long.
In short, this doesn’t work well and won’t last.
How about covering with concrete?
Setting a few stepping stones is a smart way to make a path around the roots. Pouring a coat of concrete is a different story. Concrete blocks tree roots from oxygen and water. As time goes on, tree roots need fresh air, so they’ll again grow above ground. This time, they’ll crack the concrete, making a big mess.
Should I cover tree roots with mulch then? What about gravel?
Yes, in fact, mulch is the best way to cover tree roots above ground. When you add 2-3 inches of organic mulch, you get double the benefits. It gives your landscape a clean look and moisturizes and protects the roots.
You can sub in gravel as a low-maintenance alternative to mulch. Though there are some risks. Gravel can compact the soil and heat up the ground in summer, which causes problems. If you want to go with gravel anyway, cover the roots with landscape fabric and spread no more than two inches of gravel for the best results.