Should I clear up fallen leaves or leave them?

The default in most gardens is to clear all of them, and the default in most modern advice is to leave all of them. Both are wrong. Leaves are harmful in some places and valuable in others, and the split is easy to make once you know what the harm actually is.

Step by step

1. Clear leaves off grass.Grass needs light all winter and a leaf layer excludes it, leaving yellow patches and encouraging fungal problems in the damp underneath. This is the one place where clearing is genuinely necessary rather than tidy-minded.
2. Clear them off small and evergreen plants.A drift of wet leaves over a low evergreen, an alpine, a rosette-forming plant or a small new planting smothers it and rots the crown. Lift the leaves off rather than raking across the plant.
3. Get them out of ponds.Leaves decomposing in water use up oxygen and release nutrients that feed algae. Netting a pond during leaf fall is much less work than clearing it afterwards.
4. Clear paths, steps and drives for safety.Wet leaves on a hard surface are genuinely dangerous, and they stay slippery for weeks. This is a safety job rather than a gardening one, and it also stops the leaves staining paving.
5. Check gutters and drains.Blocked gutters cause damp on walls, and a blocked gully turns the next heavy rain into a flood. This is the highest-consequence item on the list and the one most often forgotten.
6. Leave them on borders and under shrubs.On open soil between established plants, leaves are exactly what nature does: they suppress weeds, protect the surface from winter rain, feed the soil as they break down and shelter a large amount of invertebrate life. Leave them.
7. Leave a heap somewhere undisturbed.A pile of leaves in a quiet corner is overwintering habitat for hedgehogs, amphibians, insects and their larvae. Leave it alone until spring, and check before disturbing it.
8. Turn what you did clear into leaf mould.Everything you rake up is a resource. Bagged or caged, leaves rot down into one of the best soil conditioners and seed composts there is, for no cost and almost no effort.

Tips

• Running a mower over leaves on a lawn shreds them and collects them in one pass, which is far quicker than raking and produces material that rots down faster.
• Shredded leaves break down in roughly half the time of whole ones, and oak, beech and hornbeam take considerably longer than most.
• Do not put leaves on a compost heap in bulk — they are low in nitrogen and rot slowly by a different process. Compost them separately as leaf mould.
• Leaves blown into a hedge bottom are doing exactly what you would want them to do. Leave them there.
• Check leaf piles for hedgehogs before moving them, and never put a leaf pile onto a bonfire without checking it thoroughly first.

Common mistakes

• Clearing every leaf from every border — You are removing free mulch and soil improvement, destroying overwintering habitat, and creating work for yourself. On open border soil, leaves belong where they fell.
• Leaving leaves on the lawn all winter — Grass under a leaf layer loses its light, stays wet, and comes through spring yellow and patchy, sometimes with fungal damage. This is the one place clearing is required.
• Binning them — Leaf mould is one of the most useful materials a garden produces and it costs nothing but a bag and patience. Sending leaves away and buying soil conditioner is a strange trade.

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