Key Takeaways
- Wood chippings mulch works on the soil surface and causes trouble dug in. Chips on top take next to nothing from established plants; chips mixed into a bed lock nitrogen away for a season or two.
- Two depths cover almost every job: 5 to 7.5cm where weed control is the aim, 7.5 to 10cm where maintaining summer moisture is. Past about 12cm you are burying roots, not protecting them.
- Fresh chips are only for paths and clear ground. If using with plants, from a mature shrub border to a bed of new perennials, buy them – or ensure the wood chippings have sat in a heap for a few months and turned grey-brown.
- Smell the load before you accept delivery, as sour mulch can cause big issues. A heap left airless turns acid, smells of vinegar or stale ammonia, and scorches soft leaves.
- Wood chippings do not belong on seed beds or annual veg. Seedlings cannot push through 7cm of chip and mulched ground warms late, so it goes down once plants are established.
- Reckon on 75L of chip per square metre at 7.5cm, which is why a bulk bag goes faster than expected. After that it wants a light 2.5cm dressing every second or third year, never a whole new layer each spring.
I once had a client who was offered 4 cubic metres of fresh wood chip by a tree surgeon. It arrived on their drive on the Tuesday, and by Sunday they’d spread the whole lot over the borders, in places nearly 15cm deep, simply because they had nowhere else to put it. Within weeks the lavender disappeared beneath it, the geraniums started rotting at the crowns, and the roses put on weak, pale growth instead of flowering properly. By June the mulch was holding so much moisture that the borders smelled sour. I got the phone call in July and they ripped it all off and took it to the tip.
None of that was the fault of the chippings. Wood chippings are something I still use constantly, but I always apply three rules: how deep it goes, what it sits on, and how fresh it was when it went down.
Is Wood Chippings Mulch Any Good?
Wood chippings mulch is a good choice for trees, shrubs and established borders, and a poor one for seed beds and anything sown direct. On the right ground it does all four jobs I want from a mulch: holds moisture (mulched soil loses 10 to 50% less water to evaporation), starves weed seeds of light, keeps summer soil cooler, and feeds the ground as it rots. On established beds it cuts weeding time significantly when the ground is prepared properly and spot weeding is done.
It gets a bad name because people treat it as a surface rather than a mulch. Chip cut off from the soil by fabric never takes up moisture, so it stays light, skitters in the wind and ends up on the lawn. In contact with damp earth it darkens, settles and knits together. Same material, different result. This is why I am strongly against laying a weed fabric here.
Do Wood Chippings Take Nitrogen From the Soil?
A surface layer of wood chippings takes very little nitrogen from established plants; the shortage people fear comes from digging fresh chips in. Wood is nearly all carbon, and the microbes breaking it down need nitrogen. With chips on top, that borrowing happens in a thin band where mulch meets soil, above where a shrub or perennial feeds. Dig them in and it happens right through the root zone, for a season or two.
The rule I give clients is short: keep it on top, never dig it in. Two follow-ons, because they are the questions I get:
- You have spread fresh chips round your plants and are now panicking. Leave them. If something yellows in its first season, chicken manure pellets or liquid seaweed will fix it faster than raking the mulch off.
- You have dug fresh chips into a bed. It is set back, not ruined. Spread well-rotted manure on top, feed anything that yellows, and grow your hungry annuals elsewhere this year.
Where a whole border yellows and the chips are on the surface, the chips are rarely the cause. That, and the other things people blame on mulch, are in my mulch problems guide.
How Deep Should Wood Chippings Mulch Be?
Wood chippings mulch should be 5 to 7.5cm deep to suppress weeds and 7.5 to 10cm deep if holding moisture through a dry summer is the point. Choose the depth from the job, not from how much happens to be on the drive.
Chip tolerates the top of those ranges better than a fine mulch does: the pieces are irregular and lock together loosely rather than packing into a mat, so air and rain still get through 10cm of it. That is why you will see 8 to 12cm depth elsewhere. I stay lower because a border is not a woodland floor, and perennials have to come up through it every spring.
The failure modes sit either side. Skimp at 2 or 3cm and weed seed still gets its light, the layer dries out in the first warm week, and you have paid for a colour change. Overdo it and the damage is slower and worse. Chip greys within a year, so people read fade as wear and tip a whole new load on each spring; three springs of that and the border carries 12 to 15cm, roots starved of air, shrub collars permanently damp and on susceptible trees and shrubs that damp collar is where canker gets in.. Push a hand in, measure what is genuinely left, and dress it up only if it has dropped.
One rule holds at every depth: leave a clear gap of 8 to 10cm round trunks and woody stems. Chip packed against a stem holds moisture on the one part of the plant built to stay dry, and makes a covered run for the mice that overwinter in deep mulch and strip the bark off young trees at ground level. On young trees and anything fruiting I add a guard as well, a collar of 6mm mesh round the base, because the gap alone does not stop a mouse that has already moved in.
Can You Use Fresh Wood Chippings as Mulch?
Fresh wood chippings go on paths and clear ground; anywhere planted gets aged chippings, and that split is the whole answer. A fresh load is green, sappy and sometimes warm in the middle of the heap. On a path that is irrelevant. Around roots it is a gamble I do not personally take, on a mature shrub border or on new perennials.
Ageing is not complicated: heap the chips out of the way, open to air and rain, for a few months, turning the pile once or twice. You know they are ready by looking rather than by the calendar. Cream turns grey-brown, the pieces soften at the edges, white fungal threads run through the heap, and the smell goes from resin to forest floor.
Free chips from a tree surgeon can be fine, with two caveats. You take what the chipper ate that morning, so expect leaf, brash and the odd bit of rubbish and baler twine, and expect it to heat and rot faster than bought chip. And ask what the tree came down with. Most of what fells a tree is harmless in a mulch, but honey fungus and Phytophthora are the two I would refuse a load over, because both can carry in chipped root and stem.
The smell test matters more than either. A heap that has sat too long without air goes sour: the wood ferments instead of rotting, producing acetic acid and ammonia, which scorch leaves and strip low woody plants bare within days of spreading. The damage looks like drought, so the mulch gets away with it. Good chip smells of cut timber or damp woodland. Sour chip is sharp, like vinegar, or has a stale ammonia catch. If a delivery smells like that, do not spread it: tip it thin on a hard surface, turn it every few days, and the smell is gone inside a fortnight. Bagged chip sours the same way if the bags sat wet without breather holes.
Where Should You Use Wood Chippings Mulch?
Wood chippings belong around trees, shrubs, fruit bushes and established borders, and on paths; it does not belong on seed beds, annual veg or small pots. The table is how I make the call on a job.
| Where | Verdict | Depth | The reason |
|---|---|---|---|
| Trees and shrubs | Yes, aged chip, the best place for it | 7.5–10cm, 8–10cm off the trunk | Roots feed below the borrowing zone; coarse chip lasts years |
| Established perennial borders | Yes, aged chip on bare soil, no membrane | 5–7.5cm | Stops annual weeds, holds moisture; plants come up through it |
| Fruit bushes and orchard trees | Yes, aged chip, out to the drip line | 15cm, settling to about 7.5cm before you top up | Feeder roots run out to the canopy edge; the trunk gap and a mouse guard matter doubly here |
| Paths and seating areas | Yes, fresh chip is fine | 7.5–10cm over membrane | Nothing is planted, so freshness is irrelevant |
| Annual vegetable beds | Mostly no | n/a | Shallow-rooted, resown yearly, cannot be hoed through; use compost mulch |
| Seed beds and new sowings | No | n/a | Seedlings cannot push through it; the ground stays cold into spring |
| Slopes | Gentle ones only | 5–7.5cm | Chip washes and creeps beyond about 1 in 12 |
| Pots and containers | No | n/a | Blows off a dried-out pot and does nothing against vine weevil; use 2 to 2.5cm of sharp grit, or bark on acid-lovers |
Nothing goes between chip and earth in a planted bed: clear the weeds, wet it if dry, spread. The only chip I lay over fabric is on a wood chip path. Where the ground itself is the problem, poor, tired or newly cleared, I use composted wood chip rather than fresh: the breakdown has already happened in the heap, so it feeds from the first week without the nitrogen argument. Those grades sit side by side in the compost mulch range.
When Should You Put Down Wood Chippings Mulch?
Wood chippings go down in late winter on light soils, in spring once the ground has warmed on heavy ones, and always onto moist soil. Timing decides whether the mulch locks in a good state or a bad one.
Free-draining ground gets mulched earliest. On sand or chalk I spread chip in February or early March while the soil is still wet from winter, because whatever moisture is in the ground the day you cover it is what the plants get in June. Come back in May after a dry April and you seal in the drought instead. Clay is the opposite: chip is an insulating blanket, and a cold wet clay bed under 8cm of it is still cold in mid-May, so I let the sun get at it first. Either way, the day after a proper soaking is the day.
Around new plantings, hold the mulch back until each plant tops the layer by a good 2 to 5cm, and keep a 15cm ring bare round it for the first fortnight. Slugs also shelter in it, and a wet spring brings more of them. Most of what lives in a mulch is breaking it down rather than eating your plants, but tender seedlings beside fresh chip are a real risk, so I keep chip off anything soft until it is established and dust wood ash round the vulnerable ones after rain. Only close the mulch up to the stems once the layer is dry.
How to Use Wood Chips for Mulching
Whenever I use wood chips for mulching, they go down in four steps: clear perennial roots, soak the ground, spread to depth, then rake the chip off the stems. Clearing does most of the weed work, and it is the step that decides whether the mulch holds. Chip smothers annual weeds and will not beat an established perennial. Bindweed, couch grass, ground elder and docks push straight up through 7.5cm of it, and once the layer is down you cannot get at the roots without pulling the lot off.
How Much Wood Chippings Mulch Do I Need?
Wood chippings mulch takes about 25L per square metre for every 2.5cm of depth. At 7.5cm that is 75L per square metre, which puts a 10m² border at 750L before any allowance. The same border at the shallower weed-control depth takes 500L. Then round up hard. The rule I was taught is to measure honestly and near-double the answer, because every bed is bigger than it looks and chip settles as rain works the pieces together.
Under-ordering mulch is like painting a wall with half a tin: it looks done from the doorway and it is not. Our bark and wood chip calculator turns dimensions and depth into bags, settlement included. For which grade to buy, hardwood against softwood and what the composted grades are for, my types of wood chippings guide is the place.
Next Steps
We carry hardwood chips, softwood chips and composted wood chip mulch in bulk bags with nationwide delivery, all in our wood chips category. Still deciding whether wood chip is the right family of mulch at all? The comparison against bark, compost, manure and stone is in my what is mulch guide. And if the job is an odd one, get in touch and we will spec it with you.
If you would rather talk your wood chip mulch through with a person, ring Outdoor Aggregates on 0330 043 7585. The office is open 7am to 7pm, seven days a week.
Have you ever mulched a border with wood chippings? What did you use, how deep did you go, and how has it held up? Let us know in the comments.
FAQs
How often should you replace wood chippings mulch?
Wood chippings mulch is rarely replaced, they are dressed up. Chip greys within a year while the pieces are still intact, so check depth rather than colour and every second or third year add back the 2.5cm or so that has rotted into the soil.
What are the disadvantages of wood chip mulch?
The main disadvantages of wood chip mulch are that the wood chippings fade to grey within a year, shelter slugs in wet springs, and rule out sowing seed or growing annuals in that bed. The nitrogen problem is real only when chips are dug in rather than laid on top.
Does a wood chipper make good mulch?
A garden chipper makes perfectly good mulch from prunings and hedge trimmings, and young green material can go onto established beds the same day. Chips from mature trees or conifers want a few months in a heap before they go near new planting.
What plants do not like wood chippings?
Annual vegetables, salads and anything grown from small seed don’t like growing under wood chippings, being shallow-rooted, resown each year and unable to push through the layer. Trees, shrubs, fruit bushes and established perennials thrive under it.