How long does leaf mould take?

Mixed and beech leaves take about 12 months to produce a coarse mulch, or up to 2 years for a fine, crumbly soil conditioner. Oak takes around 18 months; conifer needles 2-3 years (RHS). Shredding cuts these times roughly in half.

Do I need to shred leaves first?

Shredding speeds up decomposition significantly. Run a mower over leaves on the lawn, or use a shredder. Shredded leaves can be ready in 6-9 months.

What is leaf mould good for?

Leaf mould is an excellent soil conditioner, improving structure and moisture retention. Fine leaf mould makes a great peat-free seed compost substitute.

Which leaves should I avoid?

Avoid walnut, eucalyptus, and leylandii in large quantities as they decompose slowly. Plane tree and sycamore leaves are fine but take longer.

Why is leaf mould better than compost for some uses?

Leaf mould has an excellent crumbly texture ideal for seed compost and potting mixes. It holds moisture well and is virtually free if you collect autumn leaves.

GardenCalcs.uk

Leaf Mould Calculator — Estimate Leaf Mould Yield

Calculate how much leaf mould you can make from collected autumn leaves.

Number of Bags

How many sacks of fresh leaves you've raked up this autumn — count them as you fill them.

Bag SizeA standard builder/refuse sack holds ~80 L; tall garden refuse bags ~120 L; a kitchen bin liner ~40 L.

Leaf TypeMixed deciduous and beech rot fastest; oak is a little slower. Conifer needles are slow and acidic — keep them in a separate heap (RHS).

How We Calculate This

Fallen leaves shrink by roughly two-thirds as they rot, so the finished leaf mould is about a third of the fresh-leaf volume you started with (RHS guidance: a quarter to a third).

Beech and mixed deciduous rot fastest — about 30% yield in ~12 months. Tougher oak gives ~28% in ~18 months. Leathery conifer needles lose the most volume and decay slowest — about 25% yield over 2-3 years (RHS), and the result is acidic, so keep needles in a separate heap for ericaceous plants.

Frame the heap (or bin/cage) at least 10% larger than the fresh leaf volume so you can pack leaves down, keep them moist, and let air circulate. These yields are indicative — actual reduction varies with how wet the leaves are and whether you shred them first.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.