Mulching Trees
Mulch rings around trees are good things when used sparingly and appropriately. Good practices lead to healthy trees with good vigor that benefit us all. A little mulch is a good thing, so more should be better…Right?
The benefits of mulch around trees can become detrimental when compounded with additions of excess mulch year after year.
Benefits of mulch rings:
Keeps mowers and string trimmers from the base of the tree. Tree bark is tough but constant injury from our lawncare implements can lead to tree decline and eventual death as the wounds occur in a very sensitive area where trees move water up from their root systems up into the canopy.
Prevents runoff of water and soil away from the tree.
Holds moisture where it is needed at the small root systems around newly transplanted trees.
Insulates shallow roots systems from temperature extremes
Protects root systems from compaction
Increases organic matter content of the soil underneath through decomposition of the mulch. This promotes beneficial fauna and microbes that are good for the tree.
Prevents competition from weeds.
Detriments of over-mulching
Smothering of tree roots. Roots respire just like people do. Roots need air exchange so they can grow to get better access to water for the tree. Thick layers of mulch prevent this air exchange from the surface.
This smothering also leads to decreased decomposition of the mulch itself which exacerbates the mulch depth over time.
Tree bark is designed to be exposed to air, not constant excess moisture. Burying tree bark with mulch promotes constant moist conditions that leads to fungal infection and insect infestation that lead to rotting and wounding of the tree bark at the base of the tree. Wounds in this area of the tree affect the tree the same way as mower damage would.
It hides the root flare of the tree. Wide thick root flares add to the structure and beauty of the tree.
It hides planting problems. Thick mulch just exacerbates planting issues where trees were planted too deep to begin with. This goes back to smothering issues and lack of root growth.
Excess mulch becomes hydrophobic which means that once it does dry out it is very difficult to get water to penetrate and it loses all its moisture holding benefits.
Mulch is expensive to purchase and due to its bulky nature, it’s expensive to move around and apply. A good mulching program saves money and resources. It does not need mulch additions every year. A thin layer of mulch every 2-3 years gives all the benefits of mulch while letting it break down naturally feeding the tree and its associated beneficial microbes. If you must mulch every year, fresh mulch does brighten up the landscape, some of the previous year’s mulch should be removed prior to additions of a fresh layer.