Why Mulch Around Trees?

mulch around tree

Everyone loves the benefits of having trees on a property. There’s the added beauty, the passive cooling during the hot summer months, and the feeling of being closer to nature.

Most people don’t realize that mulching around a tree is one of the easiest and most effective ways to help your tree grow and thrive. Read on to learn more about the fantastic benefits of mulch around trees!

Picking the right kind of mulch is essential if you plan to landscape trees around your business, home, or park.

When applying mulch, it’s essential to consider the different kinds of mulches and what type of climate you live in.

Mulch is a substance spread around a yard, planting beds, or tree trunk for a variety of use. Research shows a direct positive impact on tree health when mulched correctly.

Mulching helps a tree’s roots. Mulching is essential for young trees and newly-planted trees to prevent competition from grass. Mature trees thrive with mulching as well and produce better roots when mulched.

The Scientific Reasons Why You Should Apply Mulch Around Trees

Copious research backs up the idea that trees thrive when mulched. Several specific and measurable benefits to a tree’s health are shown when they are mulched.

Improve Tree Growth

According to the United States Forestry department, mulching trees can double how fast trees grow. Studies show mulch can double the growth of trees.

mulch sapling

Hardwood bark trees such as oak, maple, hickory, and birch also see substantial growth with proper mulching.

Reduce Weed Growth

A study by HortTechnology in 2016 showed a 45% reduction in weed growth the first year mulch was used and then an 85% reduction the second year used.

Organic mulches can help block weed growth. Mulch acts as a barrier between the soil and the sun. Since many weed seeds must germinate, then the mulch blocks sunlight from getting through to those weed seeds.

Increases Nutrients

As the composting process occurs, mulch adds organic matter to the soil. As organisms from the soil come to the surface to feed, they then bring down this organic matter from the mulch. Of the two kinds of mulches, organic mulches are the only kind that compost.

Reduce Water Evaporation

Because mulch acts as a barrier between the sun and soil, the water trapped in the ground evaporates slower. According to a study by the University of Washington, properly mulching trees can reduce water evaporation by a third.

Eliminate Soil Erosion

When it rains, mulch prevents the top layer of soil from washing away and preserves soil structure. Mulch also helps prevent soil compaction, which can prevent correct oxygen flow.

Temperature Regulation

Mulch helps regulate the soil temperatures. Mulch can offer protection in climates with harsh winters by keeping the soil warm. In extreme heat, mulch conserves soil moisture and keeps the soil cooler.

Types of Organic Mulch Material

Organic mulch is made from several different materials. When mulching around trees, popular mulch types include the following:

  • Shredded/chipped bark
  • Wood chips
  • Pine needles
  • Grass clippings
  • Used newspaper
  • Shredded leaves
  • Straw
  • Weed piles
  • Biodegradable food

Most tree care experts recommend using organic mulch around trees. Popular tree mulch varieties include wood chips, pine needles, bark, cocoa hulls, leaves, and other compost mixes. 

These types of mulch add organic matter to the soil, which improves soil quality and fertility.

colorful lonely tree in the field in autumn

Leaves from autumn can be used the next spring for mulching trees. Because they are easily found and readily available, leaves are easy organic mulch. 

The process for mulching leaves is relatively simple. Using a lawnmower to shred the leaves after they fall is the easiest. They can be stored in a cool, dry spot to prevent mold or fungus growth.

Types of Synthetic/Inorganic Mulch Material

Synthetic mulch comes in a variety of different materials, and popular types include the following:

  • Rubber
  • Plastic
  • Glass
  • River rock
  • Gravel
  • Stone chips

Although tree experts recommend organic mulch, synthetic mulch serves its benefits, such as being better at water retention.

How to Correctly Mulch Trees

You must apply mulch properly. An adequately mulched tree looks beautiful and reaps numerous benefits. The best time to mulch is in the spring, when new growth emerges. 

A tree possesses what’s known as a “drip line,” which is the farthest point out its canopy reaches. Spread the mulch out to that drip line. Since the soil is warmer in the spring, the tree’s roots begin to grow. 

A tree’s canopy constantly expands without trimming, so the mulch radius should be larger than the current drip line if you aren’t planning to trim back the growth.

When you apply mulch, only place a few inches on the ground. A proper depth depends on what kind of mulch is used. With less dense mulch, then approximately four inches of mulch works. If mulch is too thick or dense, then oxygen flow is limited. With fine-textured mulch, the mulch depth can sit around one inch.

Try and prevent too much mulch near the base of the tree trunk where it hits the soil. This is called “root flare,” and it’s identified by the slight swelling where the roots extend from the tree’s trunk before descending to the ground.

With organic mulch, it will need to be replaced somewhat regularly depending on the kind of organic material used. Usually, when mulch is properly applied, then it should last around 5-6 years. When the soil surface shows or signs of soil erosion are present, then that’s usually a telltale sign to pull old mulch.

Avoid Overmulching

When applying mulch, it’s essential to do it properly. An improper application of mulch can result in over-mulching.

There are several debilitating issues with improper mulching. These issues can directly stunt a tree’s root growth and root development. The telltale sign of an over-mulched tree includes a “mulch volcano” at the bottom of the tree’s trunk. Volcano mulching is never recommended.

This pile of excessive mulch around the tree smothers it. It’s a waste of resources, and a deep mulch layer around the tree trunk leads to several issues that may lead to a tree’s eventual death.

Problems Associated with Overmulching

Putting too much mulch can lead to problems with your lawn, garden, and trees. 

Disease

You don’t want your mulch to retain moisture, and an excess of mulch can lead to this exact problem. A tree that’s too moist will begin to decay. This decay, in turn, causes fungal and bacterial diseases to form in the root ball of the tree underneath the mulch. 

If a tree already has existing root wounds, then excess moisture can speed up the process of decay, making the problem worse.

If these harmful plants are allowed to grow, then they can eventually cause tree bark rot. Eventually, bark death causes the tree roots to starve, which will kill the tree.

Excess Heat

Too much mulch also creates too high a soil temperature. Excess mulch will overheat the soil and lead to inner bark death. In some cases, temperatures within the soil can reach up to 140 degrees Fahrenheit.

Young trees especially suffer, and too much mulch around a tree also prevents proper winter protection.

Oxygen Starvation

Piling mulch smothers the soil and prevents proper oxygen flow. A thick layer of mulch will block natural airflow and prevents evaporation. Trapped water also stops oxygen transfer.

When there is not enough oxygen for the tree, then its intake of nutrients is severely stunted. This can result in the death of the tree. 

Rodent Infestation

Because of the sheer volume of mulch, small animals such as mice, voles, rats, and other gnawing rodents use the mulch volcano as their burrow. These animals eat the tender bark of the tree. If too much of the inner bark is consumed, the tree will suffer. 

Because these rodents use the burrows over winter, tree damage from these critters is often not noticed until spring.

Saving Overmulched Trees

All is not lost if you have over-mulched trees. To start, assess the depth of the mulch. An inch layer of mulch is sufficient when working with denser organic mulches, whereas two or three inches is fine when working with medium-textured mulch and looser mulch.

If the soil drains well, then two to four inches of mulch is fine. Less drained soil can suffice with about an inch of mulch.

For young trees, clear out three to five inches of mulch. If you are trying to save a mature tree, clear eight to ten inches of space.

After clearing out excess mulch, make sure the tree roots are exposed. Look for the “root flare” and keep that free from mulch. Sometimes the tree is planted too deep, however, and the root flare may not be visible.

If the mulch has been stagnating for too long, then remove the old mulch and get rid of it.

If there is non-spoiled excess mulch, you can use it to mulch the drip line properly. A rule of thumb: spread mulch outwards, not upwards.

Once the mulch is reapplied correctly, then a tree should show visible signs of health, such as a better leaf and bark color.

Conclusion

Using mulch will improve tree health and encourage better tree growth. It will also prevent weeds, enhance the quality of soil, and reduce erosion.

Several mulch kinds are available depending on the landscaping needs and are relatively cheap. Not only this, but mulching is easy to apply and lasts for a long time.

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