Landscaping beds with too much mulch around trees and shrubs.
Each Spring, millions, maybe billions of yards of mulch gets applied to landscape beds and tree rings around the world.  Mulch comes in all kinds of materials, colors, and textures and it provides countless benefits in the landscape.  The look of new mulch makes a significant impact on the visual appeal of properties.  Outside of the aesthetic improvement, it provides weed control, moisture retention, and helps keep soil temperatures consistent.  The benefits are numerous, but there is such a thing as too much of a good thing.  When excess mulch builds up year after year can actually wreak havoc on the health of landscape plants.

Trunk damage to a tree exposed when excess mulch is removed.Problems with Excess Mulch

  • Suffocation – roots need air and water to expand and grow.  Too much mulch restricts airflow to the soil and the roots actually suffocate.
  • Crown and Root Rot – thick mulch layers can retain too much moisture causing the soil to stay soggy and delicate perennials and shrubs.
  • Bark Damage – mulch pushed against tree trunks (aka mulch volcanoes) softens bark and allows insects and diseases easy entry into plant tissues.
  • Root and Foliage Burn – soil temperatures can become warmer than plants prefer when thick layers of mulch are piled over the root zone.

How Much is Too Much?

A good rule of thumb for mulch depth is to maintain a 2-3″ covering over the soil.  The most popular material used for mulch is wood, but there are other materials, like stone or rubber that also do the job.  Stone and rubber tend to be easy to measure and fairly consistent in depth from year to year, but wood mulch breaks down over time.  Decomposing mulch returns humus to the soil which adds beneficial nutrients back into the landscape.  For the plants – that’s a good thing.  But if you’re trying to measure depth, it makes things a little tricky.

Since the goal is to have no more than 3″ of mulch in place at any time, the best practice for new mulch applications is to remove any mulch that has faded or become matted down.  This upper layer is usually not very attractive and can sometimes be difficult for water to penetrate.  That should expose the next layer of decomposing organic matter.  Measuring from the at-grade soil to the top of the organic layer will determine how much new mulch is needed to achieve a maximum of 3″ total.

Mulch volcano around a street tree
Over mulched tree with mulch volcano and high mulch mound

Reversing the Damage from Over Mulching

When excess mulch is present, there is a two-part approach to stopping the damage.  First, mulch needs to be moved away from the trunks and crowns of the landscape plants.  The goal is to get the mulch at least three inches away from the base of the plants.

The second challenge is to reduce the overall amount of mulch back to a three-inch depth.  When the layers of mulch are removed, fine roots will be exposed.  It takes time for these roots to move back below the surface.  To avoid shocking the trees and shrubs or having the plants dry out when the roots are exposed, this removal needs to be done in stages.

Tree ring after excess mulch has been removed.

Think you may have too much mulch in your landscape?  Let Complete Landscaping give you Green Peace of Mind and contact us today for a consultation.