Wood Chips as Mulch
In a landscape context, wood chips are a mulch material made of chipped wood — arborist wood chips are a mixed material that can include bark, wood, and often leaves, rather than a single uniform product. What is sold or supplied as wood chips varies by source, so this page treats them as a material rather than one standardized product. They are used as a surface mulch, laid on top of the soil rather than worked into it. This page explains the material itself; how much you need, general coverage and depth, comparisons with other mulches, and application around trees are covered by dedicated pages.
What Wood Chips Are
Arborist wood chips are the chipped material produced by tree work: bark, wood, and often leaves, mixed together rather than sorted into one uniform product. In many urban areas, arborist chips are available locally at little or no cost. What is sold or supplied as wood chips varies by source — some processors shred the material rather than chip it, and the resulting mix can include differing proportions of wood, bark, leaves, and needles. This variability is part of what distinguishes wood chips from uniformly textured materials such as sawdust and bark mulch, which are processed to a single consistent texture.
Using Wood Chips as Mulch
Wood chips are used as a surface mulch: material spread on top of the soil rather than dug into it. Kept on the surface, wood chips do not tie up nitrogen in the soil; a nitrogen effect occurs only at the boundary where the mulch meets the soil, not through the soil profile the way incorporating woody material as a soil amendment can.
How Wood Chips Behave as a Mulch
Wood chips are a coarse material of mixed particle sizes rather than a fine, uniform one, and that physical and chemical diversity resists the compaction often seen in sawdust and bark mulches. The material is also a slow decomposer: its tissues are rich in lignin, suberin, tannins, and other complex compounds, so nutrients are released slowly rather than all at once. Within the same batch, coarse woody pieces persist longest while any leaves or needles mixed in break down quickly. Wood chips also absorb significant amounts of water and release it slowly back to the soil. Studies have found wood chips to be one of the best-performing mulches for retaining soil moisture and moderating soil temperature. Arborist wood chips also provide substantial weed control in ornamental landscapes; the mechanisms are not fully understood, but likely include reduced light reaching the soil and lower nitrogen at the mulch-soil interface. As the material breaks down, it adds organic matter and nutrients to the soil over time.
Trade-Offs to Weigh
In clay soils, wood chips can hold enough moisture around roots and the crown to contribute to rot, so drainage is worth considering before applying a thick layer. A chip layer also hides the soil surface, which can make it harder to judge when watering is actually needed. And because wood chips break down over time, the layer eventually needs replenishing to maintain the depth you started with.
Where Wood Chips Are Used
Wood chips are commonly used as a surface mulch in ornamental beds, borders, and other landscape plantings. They can also be used as a surface mulch around trees and shrubs — in landscapes where trees are a dominant feature, arborist wood chips are considered one of the best mulch choices for that use. How to apply mulch around a tree, including ring size and placement near the trunk, is covered by a dedicated guide.
What This Page Doesn't Cover
This page describes wood chips as a material — what they are and how they behave as mulch — and deliberately stops there. It does not calculate how much mulch you need for a project; that is the mulch calculator's job. It does not provide a general coverage or depth reference, which the mulch coverage chart covers. It does not compare wood chips against other mulch materials in detail, which a dedicated comparison guide covers. And it does not cover the specifics of mulching around a tree, such as ring size or trunk clearance, which the dedicated tree-mulching guide covers.
Sources
The guidance on this page is based on the following sources.
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