Mulch: What We Use and Where We Skip It

Late April and early May is mulch season for us, and it's work worth doing well. A proper mulch layer holds soil moisture through July, keeps roots cool, starves weed seeds of light, and feeds the soil as it breaks down. Cheap insurance, honestly.

It's also the most consistently botched job in residential landscaping. So here's how we approach it, including the two habits I'd outlaw if anyone put me in charge.

What we actually use

For planted beds, our default is a composted bark mulch, pine or cedar, spread five to eight centimetres deep. Composted matters: fresh raw wood chips steal a bit of nitrogen from the soil surface as they start breaking down, while composted bark has already worked through that stage.

We top beds up every year or two rather than burying them fresh every season. If last year's layer is still mostly intact, a light refresh keeps the colour and depth right. More is not better. Fifteen centimetres of mulch suffocates roots as surely as pavement.

On the colour question, I'll say it plainly: we don't install the dyed red or jet black products. The dye isn't the issue so much as what it hides, those products are often ground up construction waste rather than bark. And the colour ages badly, going from bold to faded by August. Natural bark just goes quietly grey like a cedar fence, which suits every garden we've ever built.

The free arborist chips from tree companies deserve a mention. For back-of-property paths and utility areas they're perfectly good, and the price is right. For front beds they're too coarse and uneven to look finished.

The volcano problem

Habit number one that needs to end: mulch volcanoes. You've seen them on every commercial property in the GTA, a cone of mulch piled half a metre up a tree trunk like the tree is wearing a skirt.

Bark is not roots. Hold moisture against a trunk year after year and it invites rot, disease and rodents, and it slowly kills the tree it was supposed to help. The correct shape is a donut: mulch spread wide over the root zone, pulled back a hand's width from the trunk so the root flare stays visible and dry. Wide and flat, never tall and pointed.

Where stone mulch belongs

River stone and gravel have a real place. We use stone in our zen gardens obviously, and it earns its keep in contemporary designs, along drip edges, and in windy exposed spots where bark would end up in the neighbour's pool.

Where I talk people out of it: under deciduous trees, where every autumn becomes a leaf-picking puzzle, and packed tight around foundation plantings on south walls, where it stores afternoon heat and cooks the roots behind it. Stone is permanent in a way people underestimate. Getting it back out of a bed is a genuinely miserable job.

The fabric question

Habit number two: landscape fabric under mulch. The pitch sounds logical, a barrier that stops weeds forever. The reality after a few seasons is the opposite. The mulch on top breaks down into a perfect seedbed, weeds root down into the fabric itself, and now they're anchored better than they ever were in soil. Meanwhile the fabric is blocking water, air and worms from doing their work underneath.

We pull out more old fabric than we install. The only place it goes in our projects is as a separation layer under gravel paths and dry stream beds, where there's no organic layer above it to become that seedbed.

Deep mulch, honest materials, no volcanoes, no fabric. That's the whole philosophy. If your beds need a proper top-up this spring, it's a quick add-on to any visit.