What’s Up With Mulch?

September 22, 2021 · 2 minute read
What’s Up With Mulch?

Why mulch around trees? You see it all over: Sometimes there’s just a little around trees. Other times there are whole beds.  At your local shopping center, you may see a large mound of mulch sloping up around the trunk of a tree. What is the point of all of this?

A little mulch around trees can add a lot of benefit. First off, it can reduce the amount of grass and weeds around the base of a tree.  Reducing grass and weeds around the trees can reduce the use of lawnmowers and string trimmers around the base of a tree which lead to injury and decay. 

This tree has multiple decaying wounds from repeated lawnmower injuries. 


Organic mulch around the tree can do more than keep lawnmowers away. It can help hold moisture in the soil. It will also benefit the tree as the mulch breaks down. Decaying mulch can improve the soil and make it more like the forest soil that the tree was adapted to. 

If some is good, more is better, right?

Well…no.  Some trees have a fresh coating of dyed mulch added every year to keep a fresh look.  After years of this, the tree can get what some call a mulch volcano.

Tree roots do well in soil under mulch. Tree trunks prefer to be in the open air.  Tree roots thrive in moist conditions.  Tree trunks like to dry out. 

If mulch gets put up against the trunk of trees, roots can grow in that mulch.  A tree’s roots can grow around a tree in the mulch and eventually as the tree grows, it can choke itself.

A few inches of mulch on the ground around the base of a tree is great.  Just keep it away from the trunk.

How big should a mulch area be? 

A common arborist reply is to mulch out to the drip line of the tree.  Another answer is anything is better than nothing at all. If you do not want to give up much of your lawn, a small mulch ring is far better than grass up to the base of the tree.

What kind of mulch is best?  Double shredded hardwood mulch looks great and decomposes to benefit the soil under the tree. There is a free alternative that doesn’t look quite as nice, but has added biological benefits. Wood chips have shredded leaves, twigs, bark, and wood and no added dyes which is great for soil biology. Wood chips do not have the formal look of store-bought mulch, but they do a better job of mimicking the forest floor as the mulch breaks down.