How to Shred Leaves for Garden Mulch
Shred leaves before mulching so they do not mat. Mow dry leaves on the high setting, spread 2 to 4 inches on beds, and wait for frozen ground before cover...
Published by ThriveThyme
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How to Shred Leaves for Garden Mulch
Shred leaves before you use them as mulch. Whole leaves mat together into a layer that sheds water and smothers soil and plants. A lawn mower is the only tool you need. Spread 2 to 4 inches of shredded leaves on beds now, and wait until the ground freezes before you pile them over tender perennial crowns.
Use the Fall Leaves Desk to track each step.
Why Shred
- Whole leaves mat. University of Illinois Extension notes that unshredded leaves used as mulch tend to mat and suffocate the soil or plants underneath.
- Shredded leaves stay put. They blow around less and settle into a loose layer that lets water through.
- Shredded leaves break down faster, so they feed soil sooner and make leaf mold in about half the time.
How to Shred
- Mower: Set the deck to its highest setting. Mow when the leaves are dry. Make two passes in a crisscross pattern. Penn State and Colorado State Extension both give this method.
- Mower with bagger: Use the bag to collect shredded leaves and dump them straight onto beds or into a leaf mold bin.
- Leaf shredder or blower-vac with a shred setting: Faster for big piles that you have already raked.
- Do not wait for every leaf to fall. Penn State advises mowing as leaves come down, before the layer gets too thick to shred.
Leaves on the Lawn
You can leave shredded leaves right on the grass, within limits.
- Mow them in when you can still see grass through the chopped leaves (Illinois and Colorado State Extension).
- Penn State notes a layer up to about one-half inch is good for the lawn.
- University of Minnesota Extension says to keep mulching until you can see only about half the lawn surface. Past that, bag the extra leaves. Thick leaf mats left over winter can promote snow mold.
- Michigan State University research, cited by Penn State, found no harm to turf and no change in soil pH from mowing in oak or maple leaves.
How Deep on Beds
| Where | Shredded leaf depth | When |
|---|---|---|
| Bare vegetable beds | 2 to 4 inches as mulch | Now, after you clear the bed |
| Vegetable beds you will dig or till | 6 to 8 inches worked into the soil | Fall, so they break down by spring |
| Perennial beds, trees, and shrubs | 2 to 4 inches | Now; keep a few inches off stems and trunks |
| Tender or borderline-hardy perennial crowns | About 4 inches, or caged leaves | After the ground freezes |
Water the mulch after you spread it so it settles and stays in place.
If you dig leaves into a bed, do it in fall. Leaves are high in carbon and low in nitrogen, so fresh leaves dug in right before planting can tie up nitrogen. Illinois Extension suggests a little fertilizer after incorporating leaves to speed breakdown.
When to Mulch: Now vs After Freeze
- Bare beds, garlic, and bulb plantings: Mulch now. Bare soil does not need to wait. See what to mulch before winter.
- Tender perennial crowns: Wait. Iowa State Extension advises waiting until the ground freezes before adding a deep mulch blanket, since early mulch can delay dormancy. Illinois Extension says not to add leaf insulation until temperatures stay below freezing.
- Wire cages: For roses, lavender, and other borderline-hardy plants, set a wire cage around the plant and fill it with shredded leaves after the ground freezes. Colorado State suggests 3 to 6 inches.
Check your typical first frost on the first frost date page. Hard freeze and frozen ground usually come a few weeks after that date.
In Spring
- Pull leaf mulch back from perennial crowns as the ground thaws so new growth is not smothered.
- Leave thin, broken-down mulch on vegetable beds and plant through it, or rake it to paths.
- Toss anything still matted into the leaf mold pile.
Next Steps
- Pull out diseased leaves first. See which leaves to use or avoid.
- Mow and bag dry leaves once a week while they fall.
- Mulch bare beds now. Sow a cover crop instead on beds where the sow window is still open.
- Hold a pile of shredded leaves for crowns after the ground freezes, and put the rest into leaf mold.
Sources
- Penn State Extension, Leaves Are Treasure, Not Trash
- University of Illinois Extension, How to reuse fallen leaves at home
- University of Minnesota Extension, Fall leaf mulching is good for your lawn
- Colorado State University Extension, How to mow, compost, and mulch leaves
- Iowa State University Extension, Fall garden tasks