How to Mulch Around Trees (The Right Way)

A row of mulched pecan trees on a freshly mowed lawn of green grass.

Mulch is the ultimate protective shield for your tree. Here’s how to mulch around trees: After removing weeds, leveling the ground, and edging around the tree, spread the mulch and settle the area with water. 

Spreading mulch around the tree is an easy process, but mistakes, such as over-mulching, can kill your tree. We’ll go through every step of the mulching process so you can ensure optimal tree health. We’ll also expand on the types of mulch available, the problems of over-mulching, and the possible alternatives to this protective material.

How to Mulch Around Trees

The depth and diameter of the mulch bed make all the difference in helping your native trees grow. The amount of mulch spread around trees should range from 3 to 4 inches thick. Flower beds and vegetable gardens require different amounts of mulch. For more on mulching different parts of the landscape, here’s a guide on How Deep Mulch Should Be.  

The following steps are easy to follow and key in preventing future problems, such as volcano mulching.

Step 1: Shorten the Turf

Woman with a dog cutting grass around a tree
Photo Credit: Adobe Stock

It’s best to have very short turf around the tree prior to spreading mulch. It makes it easier to level the ground and loosen the soil, two important steps that precede mulching. 

You may temporarily remove the grass clippings to prep the ground for the next two steps, but be sure no family member disposes of them. Grass clippings may be used as organic mulch, but only after the ground is primed for spreading mulch. 

Step 2: Remove Weeds

A person's hand putting weeds in a bucket
Photo Credit: Adobe Stock

After shortening the grass, manually remove weeds growing near the tree. Weeds that grow near the root flares tend to compete with the tree and hamper its growth. To learn more about weed removal, here’s an article on How to Get Rid of Stubborn Weeds in Your Grass

Step 3: Edge Around the Tree

Edging around the tree will keep the mulch settled and protect it from strong winds or heavy rainfall. Generally speaking, mulch circles for trees should measure between 4 and 5 feet in diameter.

To achieve a perfect circle around the tree, we recommend using a tie-down strap. Use the strap to make a tight loop around the chunk of the tree. Following this, place the manual edger inside the loop and start creating a perfect mulch circle. Placing the edger inside the loop helps you keep a consistent distance (4 to 5 feet) away from the tree trunk.

Step 4: Remove Sod and Level the Ground

Close up of childs feet in rubber boots on shovel
Photo Credit: Adobe Stock

After edging around the tree, use a square-edge cutter to remove sod from the area that needs mulching. Square-edge cutters are the simplest and the most affordable sod cutter. Here’s a step-by-step guide on how to use a sod cutter. Following sod removal, use a rake to level the soil around the tree. 

Step 5: Spread Mulch

Man wearing red holding mulch
Photo Credit: Dvortygirl / Wikimedia Commons / CC BY-SA 3.0

The amount of mulch needed for trees typically ranges from 3 to 4 inches thick. Even if you’ve got a good sense of measurement, use a tape measure to double-check the mulch thickness. 

On top of that, the mulch should be kept at least 6 inches away from the tree trunk or bark. 

Do not pile up large amounts of mulch against the tree. This is what’s commonly known as volcano mulching, or over-mulching. Mulch should be distributed evenly around the tree’s root flare (root zone) and the root flare should remain exposed. 

Mulch volcanoes will retain too much moisture against the tree trunk, potentially resulting in tree diseases such as canker. Over-mulching can also reduce gas exchange (in the soil) needed for root respiration.  

Step 6: Water the Mulched Area

Watering the mulched area (about 1 inch) will settle the mulch in place. This mostly applies if you’re using organic mulch. The finer pieces will settle to the bottom and ensure maximum weed control. When high winds are expected, it’s also a good idea to give the mulch a good soaking to keep it in place. 

Step 7: Monitor the Mulch Bed

Keep an eye for unwanted plants or pests that are making a home out of the mulched area. After the winter has passed, check on the amount (level) of mulch and replenish if necessary. You don’t want it falling below the recommended level of at least 3 inches. During the fall, you consider replenishing the mulch bed to prepare your tree for the upcoming winter. 

Why Mulch Around Trees?

The trees you plant in your lawn or yard are usually native to the local environment, and adapted to a forest setting. Planting them in grassy lawns isn’t their primary habitat, which is where mulch comes in. Mulch mimics the conditions of a forest floor thus maintaining the tree’s health and root system. 

Additionally, mulch beds around trees help separate the grass from the tree area. They keep grass treatments such as mowing, fertilization, and liming away from the tree’s root system and trunk. This is important because fine root hairs of trees develop 400% more under mulch than under grass. The root hairs absorb most of the water and nutrients needed for a healthy tree.

When to Mulch Around Trees

The best time to apply mulch around trees is in the middle of spring. This is when the soil temperature is warm enough for root growth to begin. 

Generally speaking, organic mulch needs to be replaced every 1 or 2 years to maintain a healthy tree root system and garden bed. Inorganic mulch is low-maintenance, so you’ll typically need to replace it every 3 to 5 years

Signs the mulch needs replacement:

  • Mulch color is fading
  • Weeds are sprouting through the mulch
  • Mulch is fading and decreasing in volume
  • You notice fungal diseases or pest infestations 

For more on this topic, here’s an article on How Often You Should Replace Mulch

Problems of Over-Mulching Trees

Also called volcano mulching, over-mulching is a common problem among homeowners with little knowledge about this process. They just stack up as much organic material as they can up against the tree, thinking that the root flare is protected. The effects of over-mulching is especially prevalent during the spring and fall, which is when active root growth is observed in most tree species. Here are some of the main problems caused by volcano mulching:

Oxygen Starvation

Root suffocation is the most common cause of tree death. Over-mulching will cause oxygen levels to drop significantly in the soil, preventing the tree roots from respirating properly. If oxygen levels in the soil drop below 10%, root growth will decline in most tree species. Once too many roots decline, the tree will eventually die. 

Depending on the tree and soil type, symptoms of oxygen starvation may take several years to show. Once you notice any of the following symptoms, it’s generally too late to save the tree. The symptoms include:

  • Yellowing foliage
  • Abnormally small leaves
  • Poor twig growth
  • Dieback of older branches

Inner Bark Death

The death of the tree’s inner bark results from piling mulch directly against the trunk, specifically at the root flare level. Tissues in the inner bark need to breathe just like roots, so piling mulch around the trunk will hinder proper gas exchange. Once the inner bark dies due to lack of oxygen, the roots become malnourished and weakened, resulting in lower nutrient and water uptake. The tree’s health will slowly deteriorate and it will inevitably die.

Diseases

Trunk diseases will thrive in the decaying bark tissue under the large pile of mulch. Once established, disease-carrying organisms will invade the inner bark, disrupting the flow and storage of sugars. Without proper amounts of sugar, the tree will starve and die. 

Rodent Infestation

Volcano mulches can provide the perfect cover for four-legged critters such as mice and voles. They would take advantage of the warmth provided by the mulch, burrow their way through, and start chewing on the inner bark. This often goes unnoticed until the tree’s appearance starts deteriorating. 

Change in Soil pH

The soil alkalinity level may change as a result of over-mulching with organic mulch such as pine bark. This organic mulch is quite acidic, so over-mulching with it will acidify the soil. Following this, some beneficial nutrients won’t be available for the tree to absorb. Iron, magnesium, and zinc may reach high toxicity levels that would also harm the tree.

FAQ About Mulch

What are some tips to maintain mulch around your tree? 

It’s important to keep an eye on the mulch bed even after you’ve properly spread the mulch around your tree. Here are some maintenance tips:

  • Manually pull up weeds that appear in the mulch (use gardening gloves)
  • Rake the mulch after heavy snow or rainfall to prevent compaction
  • Replenish the mulch bed annually if thickness level has dropped
  • Inspect the edging around the tree to help keep the mulch bed settled

How much does mulch cost? 

The average cost of mulch per cubic yard ranges from $30 to $110, depending on the type and amount of mulch you purchase. Hiring a pro will cost an additional $20 to $45 per cubic yard. Some pros prefer to charge hourly, with costs ranging from $55 to $90 per hour

Are there some disadvantages to mulching around trees? 

Yes, there are some negatives to mulching around trees or flower beds. Here are some of the main ones:

  • When used in moist areas, organic mulch may create ideal locations for trunk rot. 
  • Organic mulch may attract rodents such as voles who use it as shelter 
  • Light-weight mulch materials can blow away in windy areas
  • Root system health may deteriorate when mulch is applied too deep around the tree stem

Seek Professional Landscaping

Mulching and protects your native trees from harsh weather and boosts your home’s curb appeal. It’s not a difficult task to complete, but could result in poor tree health if you use plastic sheet mulches or build a mulch volcano. Your best bet is hiring a local landscaping professional to choose and install the right type of mulch for your tree and soil type. 

Main Photo Credit: Adobe Stock

Jeffery Keusseyan

Jeffery Keusseyan

Jeffery Keusseyan brings his passion for nature into his love of writing to produce fun, informative content. With thorough research and hands-on experience, he provides readers with varoius lawn mowing tips and landscaping ideas.