How to Lay Bark Chippings: Depth, Top-Ups, and the Case Against Weed Membrane

Key Takeaways

• Bark chippings go straight onto weeded, moist soil in a planted border to work most effectively.
• Do not lay weed membrane under bark chippings, because it doesn’t stop weeds. Plus, bark sitting on fabric dries out, lightens and blows about.
• Bark for weed control needs a 5 to 7.5cm layer; where holding moisture is the main job, I lay 7.5 to 10cm.
• An 80-litre bag of bark covers roughly 1.5 square metres at 5cm, so a border swallows more bags than most people budget for.
• Bark chippings should be topped up with roughly 2.5cm as the layer thins – never add another full layer. Full layers that reach 12 to 15cm choke shallow-rooted plants.
• Keep bark a hand’s width, 8 to 10cm, away plant stems and tree trunks, or the damp layer rots the bark of the plant.

I’ve seen way too many properties where owners or previous landscapers just keep piling on fresh mulch every year without ever clearing out the old stuff, so it ends up stacked right against stems and trunks – where it shouldn’t touch at all. On jobs where I had taken over after years of that neglect, many trees and shrubs are completely buried under layers of woodchip mulch that was barely breaking down. I still remember one site years back where I removed more old mulch than the amount of new material I actually put down.

Laying bark properly is a relatively quick job: what goes underneath, how deep, and what happens the next year. That’s what this guide is about.

Do You Need a Membrane Under Bark Chippings?

Bark chippings in a planted border go straight onto the soil – I do not lay a weed membrane, because three things go wrong with bark on fabric:

1. The bark cannot draw moisture up from the soil, so it dries out, lightens, blows about and gets flicked everywhere by blackbirds hunting under it; and,
2. The fabric stops working anyway: bark rots down into a thin compost layer on top of the membrane, weed seeds land in it, and within a couple of seasons weeds are rooting through the fabric itself;
3. Worst of all, the sheet cuts off the one thing you are actually paying for – soil improvement. The bark feeds the ground, the worms work it in, and topping up stays a ten-minute job.

We do sell weed membrane, so weigh that against what I have just told you. It earns its place under gravel and on paths and patios, where nothing is planted and separation is required from the soil; that is covered in what to put under gravel. Besides that, the weeds a membrane is usually laid to stop are the ones it cannot: established perennials like bindweed, couch grass and dandelion push through fabric and mulch alike. Those get dug out before anything is laid, roots and all.

How to Lay Bark Chippings Step by Step

Laying bark chippings is a seven-step job: clear the ground, fork it over, water it, hold the edge, break the bark up, spread to depth, and keep it off the stems.

1. Clear every weed, and aim to dig all perennials (especially bindweed and couch grass) out by the root, not just to soil level.
2. Fork or till any compacted ground and rake it roughly level.
3. Check the moisture and water thoroughly if the bed is dry. A mulch locks in whatever state the ground is in when you cover it.
4. Hold the edge (optional): cut a shallow gutter along the border with a spade, or fit a proper edge from my guide to edging a garden.
5. Tip the bark out and break the compressed lumps up with a fork or your hands as you go, wearing a mask.
6. Spread to depth and rake even: 5 to 7.5cm for weed control, 7.5 to 10cm for a moisture mulch.
7. Pull the bark back a hand’s width, 8 to 10cm, from every stem and trunk.

How Deep Should Bark Chippings Be?

Bark chippings need a 5 to 7.5cm layer for weed control, and 7.5 to 10cm where holding moisture in the soil is the main job. The two numbers exist because the jobs are different.

Weed seeds need light to germinate, so a mulch layer for weed-control has to be deep and even enough that seeds under it start in darkness and give up. Holding summer moisture asks more of the mulch, so I lay it deeper. A skimped 2 or 3cm scattering does neither job; it just looks like mulch until June.

Depth is where budgets go wrong, because bark looks like a lot in the bag and very little on the ground. An 80L bag covers roughly 1.5 square metres at 5cm. A bulk bag of around 1,000L does 13 to 20 square metres depending on depth. Measure the border and run it through the bark and wood chip calculator before ordering to be sure.

Topping Up Bark: The 2.5cm Rule

Bark chippings should be topped up with around 2.5cm of fresh material once the layer has genuinely thinned, which on most borders means every two to three years, sooner on windy or exposed sites. There is a real disagreement on this. One camp never removes old mulch, because the decomposing layer is feeding the soil, which is true. The other strips beds back every few years, because endless topping up slowly buries plant crowns, which is also true. The answer is in the quantity.

I always rake or fork the existing layer first, because half the time the bark has faded rather than vanished and a fluff-up restores it for free. If it genuinely has rotted down, add roughly 2.5cm. What ruins borders is neither camp’s theory but the habit of adding a fresh full layer every spring: within a few years that is 12 to 15cm of mulch, shallow-rooted plants smothered, shrubs sitting in a permanent damp collar. Faded colour is just weathered bark and works exactly as well as the day it went down. And clear autumn leaves off a bark bed with a gentle rake if you don’t like the look.

By the way, if you’re here because your bark bed has problems: smells sour, grows more weeds than it stops, or has gone slimy, I cover that in a different article: bark and mulch problems.

When to Lay Bark Chippings

The best time to lay bark chippings is mid to late spring, onto moist soil, after clearing the annual weeds and before they get re-established. On light, sandy or chalky ground I bring that forward to late winter, before the soil dries out, so plants coming out of dormancy have moisture banked under the mulch through spring. New plantings can be mulched at any time of year. The only genuinely bad time to lay bark is on dry ground, which the mulch keeps dry all summer, and on frozen ground, which helps keep it frozen.

Spreading Bark Without Burying Your Plants

Spreading bark chippings safely comes down to the plants, so work from the back of the border forwards, and keep the bark off the crowns of herbaceous perennials and away from emerging bulbs. The stem gap in step seven is important: bark piled against a stem holds a damp, airless collar around it, and that rots the plant’s own bark. Oh, and white cottony threads in the bag are a harmless wood-rotting fungus, not a problem.

Which Grade of Bark Stays Where You Put It

A chunky bark grade will still be sitting in the border next summer; a fine one will be halfway up the garden. If your bark keeps ending up on the lawn, the grade is probably the reason, not just the wind.

Bigger pieces are heavier, sit into each other, and hold moisture longer, all of which anchors them. Fine material dries fast, lightens, and moves. The worst offenders are the cheap products sold as a bark and wood mix, which are usually heavy in wood shavings; shavings rot quickly, steal the most nitrogen from the soil while they do it, and look tired within a season.

Where Bark Is Not the Answer

Bark on a walked route is a different build, needing depth, edging and usually a harder-wearing wood chip; that whole job is in my wood chip and bark path guide. Play areas are different again, with their own material standard and fall-height depths, covered in play bark vs garden bark.

Next Steps

Laid on soil, at depth, and topped up lightly, bark is about the lowest-maintenance border finish there is. We carry the grades this guide works to, from fine decorative bark through to chunky nuggets that sit tight on a windy site: start with the bark chippings buying guide if you are still choosing, or go straight to our bark and mulch range. If you’re stuck on the bark-or-mulch question, mulch or bark settles it, and my guide to what is mulch covers every material in one place.

Have you mulched a border with bark recently? How deep did you go, and did the blackbirds leave it where you put it? Let me know in the comments below.

FAQs

Can you put bark chippings straight onto soil?

Bark chippings belong straight on soil in any planted border. The bark stays damp and heavy so it does not blow about, and it feeds the ground as it breaks down.

What do you put under bark chippings?

The only thing bark chippings need underneath in a border is weeded, moist soil. A membrane belongs under gravel and hard paths, not under a mulch in planted ground.

How long do bark chippings last?

Bark chippings last two to three years on most borders before the layer thins enough to need a 2.5cm top-up. The colour fades well before the function does.

Will bark chippings stop weeds?

Bark chippings at 5 to 7.5cm stop most weed seed from germinating, but established perennial weeds push up through any mulch, so those get dug out before laying.

How much bark do I need?

A bulk bag of bark, roughly 1,000 litres, covers 13 to 20 square metres at mulching depth. Measure the area, pick your depth, and let the bark and wood chip calculator do the arithmetic.