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How to Mulch Around Trees: A Practical Guide

How to Mulch Around Trees: A Practical Guide

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Whether grass or trees, mulching is an effective technique for maintaining a thriving landscape. Many experts even go as far as classifying mulch as necessary for healthy tree growth.

That’s because mulch is an integral part of trees’ natural habitats in forests. A tree needs a layer of organic matter covering the area surrounding its base, to ensure a robust root system.

Organic mulching doesn’t just keep the soil moist and aerated, but it also regulates soil temperature, enriches it with nutrients, and protects against compaction, mower damage, and weeds that compete over water and resources.

Reaping all these benefits depends on you learning how to mulch around trees. In today’s guide, I’m walking you through the process and offering pointers on the do’s and don’ts of tree mulching.

Why Mulch Around Trees?

For most trees, mulch is a vital element in their natural home.

The floor of a forest or a jungle is typically covered in leaves, twigs, wood bits, dead flowers, and a range of decomposing organic debris that serve as mulch for the trees.

When caring for plants -no matter how small or large-, the golden rule to healthy growth is to mimic the conditions of their habitat in the wild as closely as possible.

So if you’re considering planting a tree in your yard, adding mulch is a sure way to help them survive and flourish.

From boosting soil condition and introducing nutrients to preventing temperature irregularities and curbing weed propagation, mulch around trees provides plenty of pros that you can check out in more depth below.

Is Mulch Good for Trees?

Done right, mulching can be the best thing you can offer your trees.

Here’s a breakdown of how valuable a layer of organic mulch can be for landscape trees:

Lower Evaporation Rate

Mulch increases moisture levels of the soil by raising its capacity to hold in water.

It acts as a barrier that dramatically slows down evaporation at the surface of the soil, resulting in decreased water loss within a certain timeframe.

This is a great advantage for establishing strong roots with young trees as well as strengthening root systems of already existing ones.

Level Soil Temperature

If the soil around your tree becomes too hot or too cold, its growth and health will take a hit. A practical method to moderate soil temperature is by adding a layer of mulch around the tree.

It can act as a barrier that insulates the soil’s surface from external weather, preventing extreme temperature changes that can easily damage shallow tree roots. As such, the soil stays a bit cooler in summer and a bit warmer in winter, keeping your tree happy.

Plenty of Nutrients

When choosing between inorganic and organic mulch, most experts and homeowners prefer the organic option mainly due to its advantage as a source of nutrients.

Organic materials break down over time, and as a result, they release beneficial components into the soil. For example, essential minerals such as nitrogen, potassium, and phosphorus.

Not to mention, a layer of mulch will help lock the nutrients within the ground by preventing leaching. This improves the fertilization power of the soil, boosting trees’ health and saving you money in the process.

Less Compaction and Erosion

If your yard is prone to foot traffic, one way you can reduce the negative effects of repeated walking over the tree soil is by simply laying down a mulch blanket a couple of inches thick.

It can prevent the occurrence of soil crusting, compaction, run-off, and erosion to keep your precious topsoil intact.

Weed Protection

Instead of applying chemicals to combat harmful weeds and grass, mulching around your tree can offer a natural way to get the job done that’s also far less harsh on the soil (and the tree roots).

By blocking sunlight from the soil below, a mulch layer effectively deprives weeds of a key nutrient source. This will prevent the intrusive plants from sprouting and spreading, which will also keep them from competing with the tree for resources within the soil.

The result is a significant reduction in weed/grass numbers and a notable improvement in your trees’ health.

How to Mulch Around Trees

First of all, you need to make sure that you’re using the right type of mulch for the task. Generally speaking, the best mulch you can use for mulching around trees is organic, such as hardwood, dead leaves, wood bits, and so on.

From there, you need to think about your technique and timing.

The technique refers to how much mulch you’ll be laying down and how large of an area. As for the timing, I’m talking about the most favorable season for mulching.

How Much Mulch per Tree?

When it comes to the amount of mulch you need per tree, I recommend as much as it takes to cover the drip line of the tree. That’s the area surrounding the tree until you reach the edge of its canopy moving outwards.

Be sure to avoid adding mulch at the very base of the tree, specifically known as the root flare. That’s the area close to the ground with a distinct swelling radiating from the trunk.

Additionally, because organic mulch decomposes over time, you’ll need to replenish the mulch layer every so often. If you’re using fine/double-shredded materials, the reapplication process will be more frequent as they break down at a faster rate.

  • Note that you must check the depth of the mulch layer before replenishing to make sure it won’t be too thick.

How Deep Should Mulch Be Around Trees?

The thickness of your mulch layer is one of the most critical aspects of tree mulching. If it’s too thick, you’ll be dealing with the consequences of over-mulching, and if it’s too thin, your tree won’t get the full threshold of benefits.

Ideally, you should keep the mulch around your trees at a depth between 2 to 4 inches.

If the soil has poor drainage or you’re using fine/double-shredded materials, you should use around 1 or 2 inches of mulch only to avoid drainage and aeration blockage.

When Should You Mulch Around Trees?

While you can apply mulch around trees year-round without issues, spring is the best time to do so in my experience. Midway through spring, in particular, is the sweet spot as it coincides with the start of active root growth/

Can Mulch Kill Trees?

Yes, mulch can cause the death of trees, but only if you do it wrong. The most common scenario of mulching that leads to injuring or killing a tree is known as overmulching or volcano mulching.

While it may look better from an aesthetic and landscaping point of view, volcano mulching can be a serious threat to tree health. You might be thinking that you’re doing the tree a favor by giving it all the mulch available on hand, but in reality, you’re suffocating its root system.

Yes, mulch can be very beneficial to plants, but too much of this good thing can also be quite bad.

Piling mulch around trees can lead to various tree health issues, including:

  • Root starvation: An excessively thick layer of mulch prevents air from reaching the soil underneath as much as necessary for growth. As a result, the soil won’t have enough oxygen to accommodate the proper functioning of the tree’s roots.

Additionally, too much mulch hinders the evaporation process to a harmful extent as the soil pores get blocked and oxygen diffusion becomes almost impossible. With a too-low oxygen content in the soil, growth will inevitably stop.

  • Bark rot: A too-thick mulch layer can also cause the tree’s inner bark (or phloem) to develop rot. A smothered root system leads to excessive water content which means that the inner bark is constantly under high humidity levels – a lethal environment for this tissue type.
  • Heat build-up: With the soil around the tree smothered and oversaturated with water, the temperature of the area is bound to increase beyond favorable levels. The high heat triggered by volcano mulching can hinder tree growth or straight-up kill the roots/inner bark of younger trees.
  • Insect and disease: The excessive humidity resulting from overmulching creates a perfect home for pests attracted to moisture. As such, termites and other insects will further worsen the root/bark rot problem.

Can You Solve Volcano Mulching Issues?

Although you can only fix over-mulching problems if you act before the tree is damaged, the good news is that the damage takes about 3 years before it becomes too much to reverse.

Fixing the issue before that is also pretty easy, you just need to remove the excess mulch covering the trunk base and the root flare.

Final Thoughts

Mulching can be quite supportive of tree growth, but it has to be done properly. I recommend using organic mulch to reap the full benefits of the process.

Be sure to leave the tree’s trunk and root flare uncovered, and keep the mulch layer less than 4 inches thick.


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