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by Michael Kuhns, Extension Forestry Specialist
Most Utahns have planted or cared for a tree at some time in their lives. Few, however, realize the importance of mulching a tree's root system.
In order to understand the importance of mulch to a tree, think back to the last time you walked through a forest. You may have noticed that the forest floor was covered, not by grass, but by organic matter. Twigs, leaves, dead flowers, rotten wood, and other debris cover the forest floor. This material can be thought of as a mulch. It shades and cools the soil, adds organic matter and nutrients to the soil, reduces compaction, and helps keep grass and other plants from growing under and competing with the trees. Shade from surrounding trees also keeps soil and roots cool and moist in the forest.
Trees that are native to heavily forested areas, therefore, are well adapted to having a lot of organic matter covering their root systems. Trees roots are very shallow, within 6 to 12 inches of the soil surface, and this organic matter or mulch helps them survive. Roots do best under moist, cool conditions and need plenty of oxygen in the soil. These conditions are ensured by a good mulch layer.
Conditions under typical landscape trees bear very little similarity to the forest described above. The trees we plant in our yards are usually native and best adapted to a forest setting. We usually plant them, however, in the middle of grass lawns.
Sunlight hits the soil above the tree's root system much of the time, increasing soil temperature and decreasing moisture. Grass competes with tree roots for nutrients and water, but doesn't do very well because of shade from the tree.
Chemicals are used to kill weeds in the lawn and keep grass growing quickly. Compaction may be high due to foot or bicycle traffic, reducing soil oxygen. Mowers and string trimmers bump into and kill the tree's sensitive cambial layer just inside the bark, causing wounds and rot. Tree roots may have to be removed occasionally as they emerge above the grass and become nuisances.
If we think of trees as wanting forest-like conditions for their roots, it is obvious that much of what we do for our lawns is not good for trees. The solution, for healthy trees and healthy lawns, is to mulch under your trees and shrubs. This duplicates the conditions of a forest floor, improving root system health and tree health. Mulch beds around trees or groups of woody plants also help segregate tree and grass areas. Heavy fertilization, herbicides, mowing, and other treatments and practices needed for healthy grass are then kept away from tree roots and trunks. Grass can still be grown where it does best, in high light areas away from trees.
A good mulch bed should extend out at least three feet from a tree's trunk in all directions, though wider is better. Mulch can be anything organic. The best mulches are fairly coarse and woody, like wood chips or ground bark. Leaves, pine needles, compost, straw, and grass clippings also work fine. Mulch bed depth should be maintained at 4 to 6 inches, though fine mulches may tend to mat and should not be piled as deep. Edging around the mulch bed is not needed, though it can be used if you don't dig more than 2 to 3 inches deep to install it. It is better never to dig under a tree at all to avoid damaging shallow roots.
Plastic sheet "mulches" should never be used under trees or shrubs. Though they keep weeds out for a few years, they kill roots by not allowing oxygen and water into the soil. A good, deep layer of organic mulch will keep weeds out just as well and helps the tree instead of harming it. Lava rock, marble chips, gravel, or other hard, non-organic mulches also should not be used. They lead to soil compaction and do nothing to cool the soil or add organic matter. Stick with organic mulches only.
Mulching can be done at planting time, but it can also be done around established trees. Just spread a deep layer of mulch right over the existing grass. Before long the shade of the mulch will smother the grass. Any grass that comes through can be pulled or sprayed with a weed killer.
Let's learn from nature and give trees what they need. Mulch is the key to maintaining a healthy landscape, both trees and grass.
FAQs
Mulching gives your plant a competitive advantage over grass and weeds, so that it establishes roots and resumes growth more quickly than unmulched plants. Mulch also helps keep the soil moist and moderates soil temperatures.
How important is mulch for trees? ›
Mulching decreases competition from the grass. Grass robs water and nutrients from the tree's root development and delays its establishment. A properly placed mulch ring helps conserve moisture and cools the soil aiding in root growth.
What are 4 benefits of mulch? ›
Mulch helps conserve and extend available water, protects the soil from erosion, reduces competition by suppressing weeds, moderates temperature extremes, and acts as a barrier or visible marker of gardening beds to limit damage by landscape maintenance equipment.
Why is mulching necessary? ›
Mulch is a material placed on the soil surface to maintain moisture, reduce weed growth, mitigate soil erosion and improve soil conditions. Mulching (installing mulches) can help to improve crop yield and optimise water use.
Why is forestry mulching important? ›
Enhancing Soil Quality
The mulch also helps to improve soil structure, moisture retention, and reduces erosion. In addition to nutrient recycling, the mulch layer created by the forestry mulcher provides other benefits. It acts as a protective barrier, helping to regulate soil temperature and moisture levels.
What are 3 benefits of mulch? ›
The Benefits of Mulch
Mulch will reduce the amount of water that evaporates from your soil, greatly reducing your need to water your plants. by breaking up clay and allowing better water and air movement through the soil. Mulch provides nutrients to sandy soil and improves its ability to hold water. in the summer.
How does mulch protect trees? ›
Mulching plants is both functional and decorative. Mulch typically is an organic material spread on the soil surface to protect roots from heat, cold, and drought, and to provide nutrients to plants as it decomposes.
What is the disadvantage of mulching? ›
Although using mulch has many benefits, it can also be detrimental to the garden in mainly three ways: Over-mulching can bury and suffocate plants. Mulch provides a convenient hiding place for pests. Bake your plants with excess heat if done incorrectly.
What is the most beneficial mulch? ›
Organic Mulch
These mulches are impermanent materials that will break down over the course of time. These organic materials provide the best benefits of mulch, and they help condition the soil by improving its texture and adding nutrients.
Is mulch good or bad for you? ›
Mulch acts like a shield to prevent the disease movement through the water, so it significantly reduces your risk of plant diseases. Adds Nutrients and Organic Materials – Healthy soil should be made up of around 30% organic matter (by volume).
Pumice stone is a beautiful and textural alternative to mulch. It also helps repel insects and pests. Unlike other rocks, pumice rock allows water and air to pass through, which helps prevent mold and fungus.
Does mulch attract bugs? ›
Mulch can attract millipedes, centipedes, spiders, sowbugs, earwigs, ants, and even co*ckroaches crawling around in mulch beds. Many insects seek out the conditions that mulch naturally provides. These pests can be beneficial for breaking down organic mulch and can even feed on garden pests.
Is mulching worth it? ›
Mulch keeps rain from washing away your soil. As it decomposes over time, bark mulch adds nutrients to your soil. And, maybe everybody's favorite mulch benefit: it discourages weeds from popping up, keeping everything dark so the weed seeds can't sprout.
What are the disadvantages of forestry mulching? ›
You may be clearing tons of growth from your land, creating more mulch than you need for your soil. If your layer of mulch is too thick, it may help harmful insects thrive. That means you'll need to manually remove some of the mulch from your forest, which is more labor-intensive.
How big of a tree can a mulcher cut? ›
Physical Limitations
The size they can handle varies with individual models, but a general rule is a maximum of between 6- and 8-inch material. Horizontal shaft mulchers can handle much larger material, up to 30 inches, but felling trees of this size may pose a risk to the equipment or operator.
How does mulching help climate change? ›
Mulch acts as a shield and protects soil from intense heat. It prevents soil water from evaporating, and coarser types of mulch also allow for air flow above the soil surface.
Should you remove mulch around trees? ›
In addition to causing problems described below, mulch can also hide decay and dead spots on the lower trunk and major roots. Decay in this portion of the tree can cause the tree to become unstable. Keep mulch about 12 to 18 inches from the trunk for any size of tree.
Is it better to mulch or not to mulch? ›
Mulch is attractive and benefits the garden by reducing the loss of soil moisture, moderating soil temperatures and inhibiting weed growth. And, if organic mulch is used, it will improve the soil structure and add nutrients as it decomposes. So, mulch!
What are the disadvantages of mulch? ›
Disadvantages of organic mulches
The dried organic mulches are a fire risk. The heaping of the mulches can provide a perfect hiding and breeding ground for pests. They intercept light rainfall from accessing the soil. They have the potential to spread weeds, diseases, and pests.
How often do you need to replace mulch around trees? ›
Your mulch should be replaced every 1-2 years (on average). If your mulch seems to be less thick than when you first installed it, it is probably a sign that it is breaking down and dissipating into the soil. However, this is not the only reason your mulch might need replacing.
