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New Fact Sheet on Properly Mulching Trees

Posted: May 17, 2018

Spring has finally arrived, landscapers and home gardeners are ready to get out and work in their yards. Some of that work will entail spreading mulch on newly planted and existing trees. Before you do, be sure to read the new fact sheet just released by Penn State Extension’s natural resources educator Dave Jackson, entitled Mulching Landscape Trees.

Mulches are materials placed over the soil surface to enhance landscape beauty, improve soil conditions, protect plants from foot traffic and lawn equipment, and suppress weeds. Mulch is available in two major forms, organic and inorganic. Tree care professionals prefer organic mulches, such as wood chips, pine needles, hardwood and softwood bark, cocoa hulls, leaves, and compost mixes, since they decompose, improving soil structure and increasing soil fertility.

Proper mulching is one of the best ways to promote vigorous root growth and tree health. Mulching mimics the natural environment found in forests where leaves and branches blanket the soil surface, replenishing nutrients as they decompose and creating an ideal environment for root growth.

The benefits of mulching are well documented. The International Society of Arboriculture (ISA) states that properly mulching trees is one of the most beneficial practices for tree health. However, excessive or improperly applied mulch can adversely affect plants. The ISA indicates that if it mulch is applied too deep, piled against the trunk of the tree, or the wrong material, it can cause significant harm to trees.

When mulching landscape trees, Jackson suggests keeping the following points in mind.

  1. Mulch out, not up, no deeper than 2-4 inches and out to the tree’s drip line.
  2. Keep all mulch away from the trunk of the tree, allowing the root flare to show just above ground level.
  3. Use organic mulches. They provide tree health benefits as they decompose.

The fact sheet is now available on the Extension web site.