Woodchips can be really useful in a garden, especially as a mulch and soil-building material. Here are some of the best ways to use them:
- Mulch around plants: Spread 2–4 inches around trees, shrubs, perennials, and ornamental grasses. This helps retain moisture, moderate soil temperature, and reduce weeds.
- Build garden beds: Woodchips can be used in the pathways between raised beds to suppress weeds and create a clean, finished appearance.
- Improve soil over time: As woodchips break down, they contribute organic matter to the soil - particularly useful when applied as a surface mulch rather than mixed heavily into the soil.
- Reduce watering: A layer of chips slows evaporation, which can be especially helpful during hot summer weather.
- Tree rings: Woodchips make an excellent natural mulch beneath trees. Keep them a few inches away from the trunk rather than piling them against the bark.
- Garden paths: A 3–6 inch layer can create inexpensive, natural-looking walking paths while reducing mud and weed growth.
- Composting: Older, partially decomposed woodchips can be incorporated into a compost pile as a carbon-rich "brown" material.
One important distinction: fresh woodchips are generally better used on top of the soil rather than dug directly into garden beds. Mixing large amounts of fresh chips into the soil can temporarily tie up available nitrogen as they decompose. For vegetable gardens, composted or aged woodchips are preferable. For an ornamental garden, we generally use 2–3 inches of woodchips over the soil, leaving a small gap around plant stems and tree trunks - that gives you most of the moisture and weed-control benefits without creating problems for the plants.
So why does carbon matter here? Carbon is beneficial to a plant bed because it's a major component of organic matter, which helps create healthier, more functional soil. Carbon-rich organic matter helps bind soil particles into a better structure, improving both drainage and water retention. It also feeds soil organisms - fungi, bacteria, earthworms, and other microorganisms use carbon as an energy source, and a thriving soil ecosystem helps break down organic material and cycle nutrients back to your plants.
The one caveat: fresh woodchips have a high carbon-to-nitrogen ratio, so microorganisms can temporarily use up available nitrogen while breaking them down. That's exactly why fresh woodchips are best used on the surface as mulch, rather than mixed deeply into a planting bed. Over time, as they decompose, they contribute valuable organic matter and carbon back to the soil, building better beds year after year.