Wood chip mulch is the long-lasting, tidy mulch that suits paths, shrub borders and trees better than any other material. It suppresses weeds for a year or more, looks good, holds moisture and slowly feeds the soil as it breaks down. But it is also the mulch most often used in the wrong place. Spread fresh wood chip thickly over a vegetable bed, or pile it against a tree trunk, and it can do real harm.
This guide explains where wood chip belongs, how to apply it, and how to avoid the nitrogen problem that worries so many gardeners.
What is wood chip mulch?
Wood chip is made by chipping branches, twigs and small logs — often the by-product of tree surgery and garden clearance. It is a mix of wood, bark and leaves, in pieces ranging from a few millimetres to a few centimetres across. Because it contains a lot of woody material, it breaks down slowly, which is why a single application lasts a year or more.
It is different from bark mulch, though the two are often confused. Bark mulch is mostly bark, is more uniform in appearance and is usually sold in graded sizes. Wood chip is rougher, more varied and usually cheaper — often free from tree surgeons who are glad to offload a load. Both are long-lasting mulches for permanent planting, and the advice in this guide applies to both.
Fresh wood chip is different from aged or composted wood chip. Fresh chip is raw, woody and high in carbon; aged chip has begun to break down and is gentler on the soil. If you are offered a free load of fresh chip, it is worth taking — but use it in the right places, and give it time.
Where wood chip works best
Wood chip is at its best in permanent plantings that are not dug over every year: shrub borders, fruit trees, hedges, roses and ornamental beds. In these places, its slow breakdown is a virtue — you mulch once and it keeps working for a year or more, suppressing weeds and holding moisture with almost no attention.
It is excellent for paths. A 8–10 cm layer of wood chip on a path suppresses weeds, keeps feet clean and dry, and slowly rots down at the edges, feeding the soil beside the path. It is the standard path material in many productive gardens, and it is far more pleasant to walk on than bare mud.
It is good around trees and large shrubs, where it mimics the leaf litter of a woodland floor. A wide ring of wood chip under a tree keeps the grass down, holds moisture and feeds the soil as it breaks down — exactly what a tree's shallow feeder roots want.
It is less suited to annual vegetable beds. There, its slow breakdown and nitrogen demand are drawbacks, and the bed is dug over every year anyway, which mixes the chip into the soil where it does the most harm. For vegetables, straw mulch or leaf mulch are better choices. See our guide to mulching vegetables for the full picture.
The nitrogen question
The most common worry about wood chip is that it "robs the soil of nitrogen." There is a real mechanism behind this: soil microbes need nitrogen to break down carbon-rich wood, and while they are doing that work they can temporarily use nitrogen from the surrounding soil. But the effect is mostly confined to the thin layer where the wood chip touches the soil — it does not strip nitrogen from the whole root zone — and it is temporary.
The practical rule is simple: do not dig fresh wood chip into the soil. Left on the surface as a mulch, the nitrogen effect is small and short-lived, and most established shrubs and trees will not notice it. Dug in, the chip is mixed through the root zone, and the nitrogen demand becomes a real problem for months. This is why wood chip is a surface mulch, not a soil improver.
If you are mulching young or hungry plants with fresh wood chip, a light application of compost or a nitrogen-rich feed underneath the chip will cover any short-term demand. Composted wood chip — chip that has been piled and left to break down for six months or more — has already used up its initial nitrogen demand and is safe to use anywhere. Our fertiliser calculator can help you plan feeding alongside any mulch.
How to apply wood chip mulch
Apply wood chip 5–8 cm deep on beds and borders, and 8–10 cm deep on paths. Weed the area first, water the soil if it is dry, and spread the chip evenly. Keep it a few centimetres away from every stem and trunk — the "mulch volcano," where chip is piled against a trunk, holds moisture against the bark, invites rot and gives pests a way in. Leave a clear gap around every plant.
The best time to apply is spring, after the soil has warmed, or autumn, when the soil is moist. Avoid mulching very dry soil — water first. Top up once a year, usually in spring, when the layer has thinned to less than 3 cm.
If you receive a large load of fresh chip, use it for paths first, and let the rest age in a pile for six months before using it on planting beds. A pile of chip heats up as it begins to break down, and aged chip is darker, softer and safer for plants.
For quantities, our mulch calculator will work out how much you need for any area.
Wood chip and soil health
Over time, wood chip improves soil in the way a forest floor improves soil: it feeds fungi, worms and microbes, builds organic matter and improves structure. Beds mulched with wood chip for several years develop dark, crumbly, worm-rich soil beneath the mulch layer. This is slow work — wood chip is not a quick soil builder like compost — but it is real and lasting.
Wood chip also encourages fungal activity in the soil, which suits trees, shrubs and other woody plants particularly well. It is less suited to annual vegetables, which prefer the bacterially dominated soil that compost and straw encourage. This is another reason to match the mulch to the planting.
One caution: wood chip can shelter slugs, especially in damp, shady borders. Keep it away from stems, avoid over-thick layers near vulnerable plants, and use slug control as needed — see our guide to slugs and snails control.
Common mistakes with wood chip mulch
The biggest mistake is digging fresh wood chip into the soil. It is a surface mulch, and mixing it in causes the nitrogen problems gardeners worry about.
The second is the mulch volcano — piling chip against trunks and stems. Always leave a gap.
The third is using wood chip in annual vegetable beds, where it is the wrong tool. Use straw, compost or leaves there instead.
The fourth is applying it too thinly. A centimetre of chip is decoration; you need 5–8 cm to suppress weeds and hold moisture.
The fifth is using chip from diseased trees on susceptible plants. Wood chip from a diseased tree can carry disease, though the risk is low once the chip has aged and heated in a pile. If you know the source tree was diseased, compost the chip for several months before use, or use it on paths only. If you are unsure, check your local extension service for guidance.
The sixth is using chip that contains persistent herbicide residues. This is rare, but chip from trees or hedges sprayed with certain herbicides can damage garden plants. If plants show twisted, distorted growth after mulching, remove the chip and seek advice from your local extension service.
Frequently asked questions
Does wood chip mulch steal nitrogen from plants? On the surface, the effect is small and temporary, confined to the layer where chip meets soil. Dug into the soil, the effect is real and lasts months. Use it as a surface mulch, not a soil improver, and it will not harm your plants.
How long does wood chip mulch last? A 5–8 cm layer typically lasts 12–18 months before it needs topping up. Coarse chip lasts longer than fine chip, and shaded, damp areas break it down faster than hot, dry ones.
Can I use fresh wood chip straight away? Yes, on paths and around established trees and shrubs. For young plants and hungry crops, let it age for six months first, or lay compost underneath it to cover any short-term nitrogen demand.
Is wood chip safe around fruit trees? Yes — it is one of the best mulches for fruit trees. Keep it away from the trunk, spread it in a wide ring out to the drip line, and top it up each year.
Will wood chip attract termites? Wood chip near a house can shelter termites in some regions, though the risk is often overstated. Keep wood mulches a short distance from wooden structures, and check your local extension service for termite guidance in your area.
The bottom line
Wood chip mulch is the right choice for paths, shrub borders and trees: long-lasting, tidy and kind to the soil when used as a surface mulch. Keep it out of annual vegetable beds, never dig it in, keep it away from stems, and let it age before using it around young plants. For a full comparison of mulches, see our guide to mulch types or browse the guides hub.