Suppresses weeds, conserves moisture and moderates soil temperature - all from the surface.

It is a covering layer rather than a soil improver applied differently.

Weed suppression works by blocking light to the soil surface.

Moisture conservation reduces evaporation substantially and is often the larger benefit.

Temperature moderation protects roots from swings at the surface.

Over years it breaks down into organic matter, but that is a side effect rather than the purpose.

Deep enough that light does not reach the soil surface - depth is the whole specification.

Too thin and weed seedlings grow straight through.

A thin decorative layer looks tidy and suppresses very little.

Depth is maintained by topping up as the material breaks down.

Excessive depth around stems causes its own problems.

Calculating volume from area and depth before ordering avoids arriving short, which is the usual outcome.

No - it suppresses germination, and established perennials come through regardless.

Clearing before mulching is not optional.

Perennial roots left in place will push through any practical depth.

Mulching over them delays the problem rather than solving it.

Membranes beneath mulch help with some situations and create their own problems later.

Annual weed seed blown onto the mulch surface will also germinate in the mulch itself over time.

Bark held against bark stays permanently damp, which causes rot and shelters rodents.

A clear gap around every stem is left when spreading.

Piling mulch up against trunks is a common and genuinely harmful practice.

The damage develops slowly and is usually attributed to something else.

Rodents gnawing bark under the cover of mulch can ring a young tree entirely.

Pulling mulch back from stems after settling is worth doing as a maintenance task.

By longevity and appearance, since the function is much the same.

Composted bark breaks down over a season or two and feeds the soil as it goes.

Chipped bark and wood chip last longer and look coarser.

Ornamental and dyed products last longest and are chosen visually.

Gravel and slate do not decompose at all, which suits permanent planting.

Non-decomposing materials rule out soil improvement, which may or may not matter.

It draws nitrogen from the soil surface as it breaks down, which can affect shallow-rooted plants.

The effect is limited to the interface rather than the whole profile.

Established deep-rooted planting is largely unaffected.

Seedlings and shallow-rooted plants are more vulnerable.

Composted products avoid the issue, which is why they are preferred around sensitive planting.

Fresh chip is entirely suitable for paths and around established trees and shrubs.

As it breaks down - decomposing materials need annual or biennial attention.

Depth is what suppresses weeds, so a thinning layer stops working.

Composted products break down fastest and need the most frequent topping.

Coarse chip and ornamental products last considerably longer.

Non-decomposing materials need only occasional cleaning and redistribution.

The topping-up cost over years is worth including when comparing materials on price.