How to mulch around mature trees | 7 Must Know Benefits

Mulch around mature trees by placing a 2-3 inch layer of natural bark mulch around the tree’s root zone. Cover the soil with a natural mulch to stop weeds, stop water from evaporating from the soil and to improve the soil over time. Keep mulch 2-3 inches away from tree trunks to avoid rot, disease and pests. Mature trees like pine, eucalyptus, maple, oak and citrus all benefit from mulch.

Benefits of mulching around mature trees

Applying a 2-3 inch layer of natural mulch like a tree mulch will have multiple benefits for mature trees. Here are the top 6 benefits of mulching around mature trees.

Holds moisture in the soil

Mulching around mature trees helps to hold moisture in the soil by stopping it from evaporating as quickly from the surface. During heavy rain downpours, the mulch will absorb the water, slowly releasing it into the soil for the plant.

Avoids soil run off

Mulching around mature trees will hold soil in place during very heavy rain. The mulch will spread the water out more evenly across the soil surface releasing it down to the tree’s roots. Keeping good quality top soil around your tree’s roots will help it to grow strong and absorb nutrients.

Increases organic matter in the soil

Natural mulches including bark, sugar cane, straw, grass cuttings and leaf mulch will all increase the organic matter in the soil for your tree. Soil bacteria and worms will break down the organic matter from the mulch releasing the nutrients to your plant’s roots and adding it to your soil.

Increases aeration for plant roots

Worms will dig their way through to the soil surface to decompose the mulch and the soil bacteria that is breaking it down aerating the soil. As the organic matter from the mulch is mixed into the soil, more air will be added and available for tree roots to grow deep and healthy.

Regulates soil temperature

Mulch around mature trees will stop the ground from getting very cold or very hot. Mulch layers can protect your tree roots from frost or snow and keep your tree’s roots cooler during very hot weather.

Bark mulch works like a blanket in the winter and an air conditioner in the summer protecting tree roots from rapid temperature changes.

Protects tree roots from damage

Layering mulch on top of your tree’s root zone will protect tree roots from damage from pets or people walking across them. The mulch will act like a cushion, reducing the pressure and impact on the roots.

Mulching around mature trees will also protect tree roots from mowers and trimmers as it can form a barrier to passing machinery and let you know where the root zone starts.  

Stops weeds

Mulch layers work to stop weeds from growing around the root zone of your tree and competing for nutrients and water. Mulch will block the light stopping it from reaching weed seeds and preventing them from growing.

Any weeds that do manage to grow through will be easy to remove as they have had to stretch to grow through the mulch so will be weaker and easier to remove. The soil will also be softer due to the mulch and the roots will lift easily.

Why you should keep mulch away from tree trunks

Allow oxygen to reach roots

Keeping mulch away from tree trunks will allow air to flow through to the roots easily. It will also allow excess water to escape and avoid rotting the stem. If roots do not get enough oxygen, they can slow their growth, stopping the tree from growing well and can even result in tree death.

Reduce disease

Keeping mulch away from the tree trunk will avoid excess mulcher and other problems such as mold and fungus. Tree trunks that have mulch placed close to the base are more likely to grow mushrooms and toadstools which can look unsightly.

Other diseases including root rot can occur if the trunk is kept wet which can cause damage to the roots, trunk and can eventually kill the tree.

Pests

Keeping moist mulch against a tree trunk can make it easier for pests such as termites, rats, mice and ants to live and damage the tree trunk. Moist, covered places can allow these bugs to live near the tree trunk and cause damage.

Mulching around trees over grass

There is no need to add extra mulch around tree roots that are grown in grass. Mowing the grass and allowing some lawn clippings to decompose back into the lawn will be a great way to feed the tree and the lawn.

Advanced trees can grow well in lawn, however for young trees, it is best to keep a mulch layer around the drip line of the tree. This is the imaginary line that would reach the outside of the leaves.

The mulch layer can be widened as the tree grows to feed and protect the roots and offer all the benefits of mulch like weed control and keeping moisture in the soil.

Mulching around trees with exposed roots

When mulching around trees with exposed roots, keep the mulch back from the root area. This will avoid rot, insect damage or fungus growth. Treat exposed roots like you would the tree trunk and keep the mulch at least 2-3 inches away from the roots.

Mulch will move over time so use a rake to move it back from exposed roots and allow air movement.

How to mulch around an oak tree

Gather a natural mulch for your oak tree such as mixed tree mulch, bark or shredded fall leaves. Compost can also be used as mulch or mixed together with these mulch ingredients for an extra nutrient boost.

Clear the area underneath the oak tree leaf canopy of any large weeds by gently pulling them out by hand. This will avoid disturbing the soil and damaging the Oak tree roots.

Draw a line with a shovel or rake around the drip line which is the outermost leaves to determine how far out the mulch should reach.

Check the old mulch depth. For an established oak tree, use a rake to see how deep the mulch layer is to work out how much new mulch should be added.

Top the mulch level up to 2-3 inches including the depth of the old mulch. This will provide enough coverage to stop weeds while still allowing rain to get through to the soil and plant roots.

Mulching around mature trees – FAQ’s

Should you mulch around large trees?

Mulch around large trees if their root area has no other coverage. Cover bare soil with a natural mulch such as bark mulch as this will not easily blow away and will protect tree roots. Improve the soil under your tree and keep the soil temperature more regular with a 2-3 inch layer of mulch.

Is it bad to mulch around trees?

It is not bad to mulch around trees but layering too much mulch can starve the roots of oxygen. Make sure you do not mulch the trees deeper than 3 inches to avoid rot, mold, oxygen starvation and a soggy base at your trees.

Do you need mulch around trees?

Trees benefit from protection around the root zone from mulch and it will help them grow stronger, larger and healthier. Mulch as benefits such as water retention, improving the soil and protecting tree roots from being stepped on. If you already have a covering of grass around mature trees, leave the grass and keep it mowed regularly.

Does mulch around trees kill them?

Mulch around trees will only kill them if it is laid thicker than 4 inches or is placed against the tree trunk. Both of these can cause rot, starve the roots of oxygen or heat up the soil too much as the mulch breaks down and traps heat. Keep mulch layers to a maximum of 3 inches thick to allow extra heat to escape and water to come through to the roots.

Mulching around mature trees – Summary

Mulching around mature trees will benefit the tree in the long run as it slowly breaks down and improves the soil. Choose a natural mulch to feed the soil microbes and worms and you will build a healthy ecosystem under your tree canopy.