Thanks to the University of Maryland/Maryland Grows this informative article on how mulch volcanoes kill trees.

I’ve been a bit twitchy lately. I keep seeing mulch piled high around trees and it makes me more than a little baffling. Those mulch volcanoes are so very bad for trees. 

Why? They hold moisture against the bark, inviting rot, pests, rodents, and disease.

With mulch, less is more. One to three inches is all you need. 

Done right, mulch can be a good thing. It suppresses weeds, holds moisture, prevents soil compaction, moderates temperature, and improves soil structure when it breaks down.  

Mulch can be attractive and create a protective barrier between lawns and plantings. It creates a no-go zone, keeping mowers and weed whackers from damaging tree bark.

A ring of mulch around trees also keeps thirsty grass from robbing tree roots of much-needed water. Water passes more easily through mulch than turf. 

But too much of a good thing is bad. Very bad. So many plants die an early death due to excessive applications of mulch. 

One client had lost three trees in one spot and called me for help. I nearly drove off the road as I approached her home. There were 17 inches of mulch, the bark was black and mushy, and the tree was dead as a doornail. 

Once you start looking for them, you’ll notice mulch volcanoes everywhere. My phone is full of photos of these dastardly cones.  

I can’t save all the trees, so I’m enlisting your help. Don’t let mulch volcanoes happen on your watch.  

Know that the type of mulch you choose is important, too. 

Shredded bark mulch is the most popular choice for flower, tree, and shrub beds. It resists compaction, looks good, and is readily available. 

Avoid using chunkier nugget mulches where water flows regularly. Those nuggets float, so they tend to move – sometimes quite dramatically – in heavy rains. 

Consider stone mulches carefully. Leaves, debris, and weeds are difficult to remove, and stones can dry plants with the heat they reflect. Baked Alberta spruce, anyone? 

Also, avoid mulch made from recycled tires. It blocks the flow of air and water to plant roots and can leach harmful chemicals. Plus, it doesn’t break down to feed the soil. 

Regardless of the type of mulch you use, keep it an inch or two away from trunks. This avoids moisture buildup that can cause rot and invite insects and disease. 

Learn more about mulching from the Home and Garden Information Center: Mulching Trees and Shrubs. 

I also encourage you to look at mulch alternatives. Not only are they more sustainable, they can save the cost and effort of applying and reapplying traditional mulch. 

Plant groundcovers or a mix of perennials and groundcovers around trees to create a plant community that supports pollinators, beneficial insects, and wildlife.  

Try using groundcovers instead of mulch in your flower beds. Newspapers and straw or untreated grass clippings work well in vegetable beds as does an inch or two of compost.

So join in the mulch mania. Toss it forth with glee but not too deeply. Or explore some mulch alternatives that not only block weeds, hold moisture, and feed the soil, but provide vital habitat.  

By Annette Cormany, Principal Agent Associate and Master Gardener Coordinator, Washington County, University of Maryland Extension.

This article was previously published by Herald-Mail Media. Read more by Annette.

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