What to Do With the Wood Chips After Tree Work

At the end of a removal or a big prune, the crew asks whether you want the chips. Most people say no automatically, and a fair number of those people go out and buy bagged mulch a few weeks later. Fresh chips are a genuinely useful material if you have somewhere to put them.

They are also not right for everything, and there are a couple of situations where keeping them is a bad idea. Here is how to decide on the spot.

Why Wood Chip Mulch Is So Good for Trees

A layer of coarse wood chips over a root zone does several things at once. It holds soil moisture through our dry spells, evens out soil temperature, suppresses the lawn that competes with tree roots, and slowly feeds the soil food web as it breaks down.

Arborist chips, which include bark, wood, and leaf material in mixed sizes, are closer to a forest floor than uniform bagged mulch and break down into better soil structure over time. For heavy Calgary clay, that gradual organic input is worth a lot.

Where to Put Them and How Deep

Spread chips 5 to 10 centimetres deep over as much of the root zone as you can manage, ideally out to the drip line and beyond. Keep them pulled back a hand's width from the trunk so the bark can dry, because a mulch volcano piled against a trunk causes rot and invites rodents.

They also work well on paths, in shrub beds, around a fire pit area, and under a play structure. What they are less suited to is a formal front bed where appearance matters, since fresh chips are coarse and vary in colour.

The Nitrogen Myth

People worry that wood chips rob nitrogen from the soil. On the surface, as mulch, that effect is limited to the thin zone where the chips meet the soil, and established trees are unaffected.

The caution applies if you till fresh chips into soil, where decomposition really does tie up nitrogen for a season. So use them on top, not mixed in, and skip them in a vegetable bed where you are direct seeding.

When Not to Keep the Chips

If the tree came down because of a disease, ask before keeping the chips. Elm material is restricted in Alberta because of Dutch elm disease and should never be stored on site. Chips from a tree with certain root diseases are also best hauled away.

For most storm damage, structural removals, and routine pruning, the chips are fine. When in doubt, ask the crew what the tree had, because they know what they just cut.

Practical Realities of a Chip Pile

A mature tree makes a lot more material than people picture, often several cubic metres. A chip truck dumps in one spot, and moving that pile by wheelbarrow is a weekend of work, so decide where you want it before the truck arrives.

Fresh piles heat up as they compost and can steam and smell for a few weeks. Spread them out reasonably soon rather than leaving a deep heap sitting on the lawn, which will kill the grass underneath.

Firewood Is a Different Question

Chips and firewood are separate decisions. Large rounds can be kept for firewood, but green wood needs a year or more of drying, split and stacked off the ground, before it burns well. Some species make poor firewood regardless.

And again, elm is restricted. If you want rounds left, say so before the crew starts cutting, because how the tree is dismantled changes once they know. Aardvark Tree Care can leave chips, leave rounds, or haul everything away, whichever suits the yard.

Chips on top of the soil feed a tree; chips tilled into the soil borrow nitrogen for a season.