How to use a garden riddle
Updated: 21 October 2026
The mesh has clogged, the heap smells sour rather than earthy, and the sticks that stayed in the sieve are heading for the council bin. That is the usual way a first riddle session goes wrong. You use a garden riddle on compost that is already crumbly and dry, over something that can catch the fines, and you put the coarse fraction back. The models sit on the [compost sieve comparison](/hub/raised-beds-greenhouses-and-compost/compost-sieve). Peter F. wrote this method on 19 October 2026 from Royal Horticultural Society guidance and UK compost notes. If you buy through our links, we may earn a commission at no extra cost to you.
The mesh has clogged, the heap smells sour rather than earthy, and the sticks that stayed in the sieve are heading for the council bin. That is the usual way a first riddle session goes wrong.
The mesh has clogged, the heap smells sour rather than earthy, and the sticks that stayed in the sieve are heading for the council bin. That is the usual way a first riddle session goes wrong. You use a garden riddle on compost that is already crumbly and dry, over something that can catch the fines, and you put the coarse fraction back. The models sit on the compost sieve comparison. Peter F. wrote this method on 19 October 2026 from Royal Horticultural Society guidance and UK compost notes. If you buy through our links, we may earn a commission at no extra cost to you.
Our top picks
| Badge | Product | Motion | Mesh | Weight | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Spear & Jackson Spear & Jackson garden riddle | Shake or knock | 10 mm fixed | 586 g | 8.7 | about £14.95 | View offer |
| Best value |  ADEPTNA ADEPTNA five-mesh sieve | Seat, then tip | 3 mm to 12 mm | 890 g | 7.3 | about £14.95 | View offer |
| Alternative |  Haxnicks Haxnicks Easy Riddle | Rock in the barrow | 10 mm on maker page | 250 g | 5.9 | about £9.99 | View offer |
On this page
Sift it only when it is ready and dry
Ready compost breaks in the hand. It smells earthy, not of ammonia or of a bin that has gone slimy, and it does not smear when you pinch it. Wet, sticky compost balls up and blinds the holes. A HOTBIN note makes that point plainly: dry the material before you sieve, because wet compost clogs. Wait for a dry day, take small amounts, and knock the mesh clear when it blinds.
A fine mesh makes a wet heap worse. About 10–12 mm is the everyday grade for a bin. A 3 mm plate is only for a small, dry batch. Which hole matches which job is on the garden sieve mesh size page. If the bin is still hot, wet, and full of intact stems, leave it. Sieving will not finish an unfinished heap.
Set the sieve on a barrow, bucket, or sheet
The fines have to land somewhere you will use. A wheelbarrow is the usual support for a frame near 30–40 cm. A bucket suits a taper sifter built for a rim of about 30 cm. A sheet or a trug is enough for a 20 cm pan, and it is a poor plan for a spadeful from a full bin.
Put the sieve down so it cannot walk. A round riddle perched on a narrow bucket rim will tip when you shake it. A folding poly-mesh riddle can sit in the barrow and rock, which is the motion those listings describe. Do not hold a loaded metal sieve at arm’s length for half an hour. Hand strain is the practical hazard. If the only support you have is your hands, take a smaller load.
A thin layer, then a rock or a shake
Tip in a layer you can still see the mesh through. A full pan looks efficient and then packs into a cake, especially if any damp remains. Haxnicks’ own description of the Easy Riddle is a rocking action, using the mesh on the base and the sides, and reviews that like it say not to overfill. A round steel riddle is more of a shake or a gentle circular knock. You are not trying to force stones through a 10 mm hole. If they will not pass, they are the overs.
When the mesh blinds, knock the back of it. Do not hose a metal sieve and hang it up wet. If you are still choosing diameter and material, the garden sieve buying guide is the shopping page.
Keep the coarse fraction
What stays on the mesh is not rubbish. The Royal Horticultural Society’s account of riddling a heap is that what falls through is used, and what stays goes back on top. Sticks, twigs, and unfinished lumps are the next batch’s carbon. Throwing them away is how a heap shrinks into a bag of dust and then stops working.
A sieve does not kill weeds. The Royal Horticultural Society, on homemade potting mix, tells you to keep out oxalis, horsetail, and ground elder. Pull them out while you can see them. If the overs are mostly stones, they can go on a path or a soakaway trench you already intended. If they are woody compost, they go back on the heap.
Stop before seed trays
Sieved homemade compost is a mulch, a soil improver, or part of a rough potting mix for tougher plants. It is a poor medium for sowing seed. The Royal Horticultural Society’s peat-free advice is that homemade potting compost is best avoided for seed sowing because of fungi. Sieving does not remove that risk, and it does not pasteurise the heap. A 5 mm mesh appears in the John Innes loam method, followed by a stated heat treatment. That heat step is a separate process. This page is not an oven recipe, and it does not merge times from other booklets.
Stop altogether when the soil may contain oil, asbestos, or unknown builders’ waste. Wear gloves. A riddle is not a way to grade contaminated ground, and a laboratory test sieve is a different tool. If you cannot tell what the soil is, leave it.
Common questions
Where do I rest the sieve?
Rest a frame of about 30–40 cm on a wheelbarrow or a wide trug so the fines fall into something you can move. A bucket suits a sifter built for a rim of about 30 cm. A sheet is a fair catcher for a small pan, and a messy one for a whole bin. The sieve should sit, not hang from your wrists. If it rocks off the support, the support is too narrow for that frame.
How much do I put in at once?
Put in a thin layer, thin enough that you can still see mesh before you start. A heaped pan packs and clogs, particularly if the compost is even slightly damp. UK how-to notes say small amounts on a dry day, then knock the mesh clear and repeat. A warning against overfilling on a folding riddle is the same idea.
What if the compost is wet?
Leave it. Wet, sticky compost balls up and blinds the holes, which is the point made in the HOTBIN sieving note. Spread it under cover or wait for a dry spell, then sieve. Knocking harder pushes paste into the mesh. A finer hole clogs first, so a 3 mm plate on a damp heap is the combination to avoid. Dry compost that smears when pinched is not ready, even if the calendar says it should be.
What do I do with sticks left on the mesh?
Put them back on the heap. The Royal Horticultural Society describes riddling that way: use what falls through, and return what stays. Those lumps and twigs are unfinished compost, not waste. Stones can go somewhere you already use stone. Roots of oxalis, horsetail, or ground elder should come out by hand, because a mesh does not kill them. Binning the overs is how the bin loses the woody fraction it still needs.
Can I sow seeds in sieved homemade compost?
Do not use it as seed compost. The Royal Horticultural Society says homemade potting mixes are best avoided for sowing because of fungi, and sieving does not change that. Use the fines on beds, as a mulch, or in a rough mix for plants that are past the seedling stage. A 5 mm sieve in the John Innes method is only the grading step before a heat treatment that this page does not turn into a kitchen recipe.
When should I stop and not sieve the soil at all?
Stop if the ground may contain oil, asbestos, or unknown builders’ waste. A garden riddle does not make that soil safe, and it is not a laboratory sieve. Stop if the heap is still wet and unfinished. Stop before you treat the fines as sterile seed compost. If you only need leaf mould or a mulch, a coarser riddle and a return of the sticks is enough. You do not have to grade every bucket to dust.
Related pages
Sources
Public UK and manufacturer sources, last checked on 19 October 2026. ASIN prices and stars are from the amazon.co.uk listings in this comparison.
- RHS, How to make your own potting mix (retrieved 19 October 2026)
- RHS, Four steps to perfect compost (retrieved 19 October 2026)
- RHS, John Innes potting compost (retrieved 19 October 2026)
- RHS, Peat-free compost choices (retrieved 19 October 2026)
- Gardeners' World, How to make a soil sieve (retrieved 19 October 2026)
- Haxnicks, Easy Riddle (retrieved 19 October 2026)
- Spear & Jackson, Garden riddle (retrieved 19 October 2026)
- Consumer Rights Act 2015, sections 9 and 11 (retrieved 19 October 2026)