How to Mulch Your Garden the Right Way

Why mulch matters

Bare soil loses moisture quickly, bakes in summer, and invites weeds. A layer of mulch acts like a protective blanket: it slows evaporation so you water less, shades out weed seeds so fewer sprout, and keeps the soil temperature steady. Organic mulches add another benefit — as they decompose, they feed the soil and improve its structure.

Choose the right mulch

Different mulches suit different jobs. Straw and shredded leaves are ideal for vegetable beds, because they break down quickly and enrich the soil. Wood chips and bark last longer and suit paths, trees, and shrubs. Grass clippings work in thin layers, and compost itself makes an excellent, nutrient-rich mulch. Choose an organic mulch for beds, and save stone or gravel for areas where you don't want decomposition.

Apply the right amount

Spread mulch about two to three inches deep — enough to block light and hold moisture, but not so thick that it smothers the soil or rots plant stems. Keep the mulch a couple of inches back from plant stems and tree trunks, since mulch piled against them traps moisture and invites rot and pests.

When to mulch

Mulch in spring after the soil has warmed and seedlings are established, and again in fall to protect soil and roots through winter. A spring application is the most important, setting the garden up for the hot, dry months ahead. Replenish whenever the layer thins, usually once or twice a year.

Mulch mistakes to avoid

• Don't pile mulch against stems and trunks, which causes rot.
• Don't use grass clippings treated with herbicide.
• Don't apply mulch over dry soil without watering first.
• Don't use a layer so thick that water can't reach the soil.

Organic vs inorganic mulch

Organic mulches, like straw, wood chips, and shredded leaves, break down over time and feed the soil as they do. They're the best choice for vegetable and flower beds, where improving the soil is part of the goal. Inorganic mulches, like stone or landscape fabric, don't decompose and last for years, which suits paths and areas under trees and shrubs.

Choose based on the job. Feed your growing beds with organic mulch, and use longer-lasting materials where you simply want to block weeds and hold the ground in place.

Refresh mulch through the season

Mulch breaks down over time, so it needs topping up to keep working. Check beds every couple of months, and add more whenever the layer thins below about two inches. Organic mulches decompose fastest in warm, wet weather, so expect to replenish them mid-season.

Keeping a steady mulch layer means you never give weeds a window of bare soil to colonize. A quick top-up is far easier than reclaiming a bed that has gone weedy.

Mulch around trees and shrubs

Mulching trees and shrubs keeps roots cool and moist and protects trunks from mower damage. Spread mulch in a ring a few inches deep, but keep it pulled back from the trunk so the bark can breathe. The classic “volcano” of mulch piled against a trunk invites rot and pests — a flat, even ring is correct.

Choose the right depth for each mulch

Finer mulches like compost and shredded leaves can be applied thinner, around two inches, while coarser mulches like wood chips can go a bit deeper. Too thick a layer of fine mulch can form a crust that sheds water, so match the depth to the material you're using.