Trees are such important components of our landscapes. A healthy tree adds thousands of dollars of value to your home, plus it gives you shade, beauty and wind protection. What can we do to help our trees live long and healthy lives?
One important practice is to add a mulch ring to newly transplanted or young trees planted in lawns. So many newer landscapes have trees planted in the middle of the lawn in the front yard. Adding a mulch ring is one of the best things you can do to help your tree transplant successfully and grow vigorously over the long term.
Why are mulch rings so helpful?
A mulch ring protects the bark.
Installing a mulch ring around the trunk means you no longer have to mow or string trim around the base of the tree. This is a good thing because if you happen to string trim the bark or bump the trunk with the mower, these injuries can seriously damage the tree. In fact, trees that get nicked or bumped every time the grass is mowed usually end up dying from the bark damage.
This tree has grass growing right up to the base. The bark is vulnerable to damage from mowers. The tree’s root system is competing with the grass for oxygen, water and nutrients.
Most people don’t realize that part of the tree that conducts water and nutrients up and down the tree is actually just right under the bark’s exterior, not in the center of the trunk. Protecting the bark from damage is really important to the long term health and beauty of the tree.
A mulch ring helps a transplanted tree grow new roots quickly.
Recently planted trees are struggling to grow a new root system. When the tree is planted, it has only 5-10% of the roots compared to the same size tree growing in a field. This means the tree is very vulnerable to not being able to take up enough water to support the branches and leaves. Trees that can’t take up enough water either develop dead branches or die.
This mulch ring is too small and doesn’t have any edging. Over time, the grass will grow up to the trunk.
When grass grows up over the root ball to the trunk, the grass roots compete for oxygen, water and nutrients with trees roots. This mean that the tree root system is already at a disadvantage.
When you prevent grass from over the rootball of the tree by installing a mulch ring, the tree can grow a new root system much faster. This means the period during which is it really vulnerable is much shorter and you end up with a healthier tree. In fact, research has shown that trees with mulch rings grow up to 20% faster than trees with grass growing up to the base of the trunk.
Here are the steps to install a mulch ring.
1. Remove the grass, but carefully. I use a shovel to dig up the grass in a circle around the tree. You want the radius of the circle to be at least 3 feet. In other words, the distance from the trunk to the circle should be at least 3 feet.
Notice how healthy the trunk of this Kentucky coffeetree is. And notice the mulch ring! Photo courtesy of Vern Wilkins, Indiana University, Bugwood.org
You can make the mulch circle larger if you want to. Some people bring the mulch up to the tips of the branches, which is also called the dripline. Be careful if you’re working on a young tree that’s been planted for a few years. You don’t want to dig too deep and damage the tree roots.
2. Install edging at the edge of the circle. This is important because the edging prevents the grass from growing back into the mulch circle. Metal or plastic roll top edging works fine.
3. Dig a slight trench against the inside edge of the edger to keep the mulch from falling into the grass.
4. Apply mulch such as wood chips, shredded wood mulch, or pine needles 3-4 inches deep inside the circle. Pine needles work really well for evergreen trees like pines and spruces. Put the mulch directly on the soil surface. Don’t bother using landscape fabric or plastic under the mulch. Mulch on top of landscape fabric will quickly blow away.
5. Avoid these common practices.
If your adding a mulch ring to a tree that was transplanted several years ago, be sure to keep the mulch at least 3-6 inches away from the trunk. If you get too much mulch up against the trunk, it keeps the trunk too moist. If the trunk is too moist on a regular basis, diseases are much more likely to enter the tree and cause damage. If you’re planting a new tree in a lawn area, don’t put mulch on top of the root ball except at the outer edges. Check out this graphic from the International Society of Arboriculture for details.
If a tree is planted in a bed that already has mulch, there’s no need to create a separate mulch ring.
Don’t use rock mulch for a mulch ring under a tree. It will be a nightmare to keep clean and doesn’t provide the same healthy environment for tree roots.
Also, don’t build up the soil around the trunk of the tree. Sometimes people like to do this to make the base of the tree more attractive. They install a little retaining wall, fill it with soil and even plant flowers in it.
This is a big no-no. Once again, you run the risk of keeping the trunk too moist so that disease might enter the trunk. But also, the soil on top of the trunk means the roots are being smothered. Many people don’t realize that roots need oxygen from the air to grow and function properly. So don’t put a bunch of dirt on top of the roots that prevents air from getting to the roots.
To review, add mulch rings to small or medium size trees planted in the middle of lawn areas. Carefully remove the grass, install edger, dig a mulch trench and fill the circle with wood mulch. You’ll keep your tree’s bark intact and healthy, thereby giving the tree a better chance to grow a healthy root system. Years later, you’ll be rewarded with a glorious, thriving tree.