We garden on sandy loam over gravel. It works in February, it is generous in April, and by late June it has the texture of demerara sugar. Water goes straight through it and takes the feed with it.

Organic matter is what fixes that. It behaves like a sponge, holding water in the root zone, and it gives the soil something to hold nutrients on. On heavy clay, compost does the opposite favour and opens the structure up. On our ground it is the difference between a cutting bed that carries on through August and one that gives up in July. Bought compost does the same job and costs money. The garden makes the raw material for free.

Most guides give you a carbon to nitrogen ratio, which is no use when you are stood over a barrow with a fork. Here is the version we use.

Greens are wet, soft and fresh. They rot fast, they heat the heap, and alone they turn to slime. Grass clippings, spent annuals pulled green, soft prunings, nettles, peelings, coffee grounds, dahlia foliage after the first frost.

Browns are dry, tough and dead. They rot slowly, they hold the heap open so air gets through, and alone they sit there for years. Autumn leaves, straw, dry sunflower and sweetcorn stems, plain brown cardboard, woody prunings.

Aim for roughly equal volumes as you build: a barrow of green, then a barrow of brown. Sloppy and smelly means too much green. Dry and unchanged means too much brown. Those are the only two readings you need.

The autumn problem

September hands you a mountain of green and October a mountain of brown. Build one week's worth then the next and you get a sour layer under a dry one, which is exactly what our first heap was. The fix is to hoard. We keep a pile of leaves and a stack of flattened cardboard beside the bays from early September, so every barrow of green stems gets a barrow of brown on top. Clippings in particular will mat into a stinking layer on their own, so mix them in the barrow before they go near the heap.

We have run all three here. There is no best one, only the one that fits your space and how much you generate.

What drives speed is volume. A cubic metre will heat itself; a dustbin's worth will not. That is why three small bins dotted round a garden rot slower than one decent bay.

Most of what a garden produces can go on the heap: spent annuals, clippings mixed with browns, soft prunings chopped small, peelings, tea leaves, coffee grounds, torn brown cardboard with the tape off, straw, old potting compost, and annual weeds pulled before they flower. The exclusion list is short, and every item earns its place.

• Perennial weed roots. Bindweed, couch, ground elder and dock survive a home heap, and you will replant them across the garden with the finished compost. Drown them in a bucket for six weeks first, then add the sludge
• Weeds that have set seed. A home heap rarely runs hot enough for long enough to kill viable seed. Groundsel and willowherb will come back to haunt you
• Cooked food, meat, fish and dairy. They rot happily, and they bring rats. Rats in a compost bay are a problem you only solve once you have one
• Glossy and coated card. Magazine paper and laminated packaging either refuse to break down or shatter into flakes you pick out of beds for years. Plain brown corrugated is the one you want
• Diseased material we simply bin, rather than find out the hard way across a hundred beds

Turning means forking the whole lot out and back in, so the dry outside ends up in the warm middle and air gets through. It speeds things up considerably, and it is heavy work.

Our honest position after six seasons: turn once, rarely three times. One turn, six to eight weeks after a bay is filled, takes about forty minutes and pulls the finishing date forward by months. It catches the dry edges before they set hard and shows you whether the mix was right while you can still fix it with leaves or a hosepipe. After that the returns drop off sharply. A heap left alone still finishes, four months or so later, and that is what we do with our third bay. If you have a job and a back, leaving it is not a failure.

Finished compost is dark brown, crumbly, and smells of woodland floor. Squeeze a handful and it holds together loosely, then falls apart. You should not be able to tell what anything used to be, apart from the odd twig and a stubborn avocado stone, which you throw in the next bay.

The test we use is simpler. Push your hand into the middle. If it goes in easily and comes out with soil-like material rather than recognisable stems, it is ready. If you meet resistance and pull out something stringy, give it three more months. It does not have to be perfect either: lumpy compost is fine as a surface mulch, which is where most of ours goes. Keep the fine material for sowing and potting and spread the rough stuff.

Three failures cover almost everything, and all three are the same problem seen from different angles.

Rats are the one failure with no repair, only prevention: no cooked food, no meat, no dairy, and fine mesh under the bay if you are near open ground.

Leafmould is a separate thing from compost and worth keeping separate in your head. Compost is made by bacteria working fast and warm. Leafmould is made by fungi working slowly and cold, and it gives you a different material for a different job. It is also the easiest useful thing you can make in a garden: no ratio to get right, no turning, no real way to do it badly.

Collect fallen leaves. Any deciduous leaves work, though oak, beech and hornbeam give the finest result and plane and sycamore take longer. Then pick a container.

1. The bin bag method. Fill a black bin bag with damp leaves, packing them down and watering as you go if they are dry. Stab the bag a dozen times with a fork, tie the top loosely, put it behind the shed.

2. The wire cage method. Four stakes and a length of chicken wire, a metre square, filled and trodden down. Better for volume and much easier to get at. We have three along the hedge line.

Then wait. The only thing that ruins leafmould is letting it dry out completely, so shade behind a building beats a sunny spot.

Two-year leafmould, sieved and mixed half and half with garden compost plus a little sharp sand, makes a decent peat-free seed compost. We have sown into it for four years. Be honest about its limits: it is low in nutrients, so it conditions rather than feeds, and anything staying in a pot for months needs feeding alongside it.

• It takes a year. The six-week compost you read about needs everything shredded and turning every three days. A normal heap built in October is ready the following autumn
• You will not make enough. Home composting reduces the bill rather than removing it
• The first year is the worst. Nothing finished, nowhere to put material, no rhythm. It gets easier from the second autumn
• Weed seeds get through. Use home compost where you can see and pull what appears, and keep bought or two-year material for sowing
• Two bays beat one, always. A single container is permanently full and permanently unfinished

Here is what is coming out of our borders this weekend and where each thing is going.

And then sow into the space

The beds you clear need not sit bare until March. An autumn sowing roots through the winter and flowers weeks earlier than a spring one, and the ground stays covered while your heap gets on with it. Cornflower 'Black Ball', Larkspur 'Giant Imperial', Ammi majus, Nigella 'Miss Jekyll' White, Corncockle, Clary Sage 'Oxford Blue' and Poppy 'Flanders Red' all go in now and overwinter outside, and Calendula 'Wintersun' was bred for it. The month-by-month detail is in the Autumn-Sowing Handbook.

For a bed staying empty, cover it. Phacelia is the one green manure we grow and stock: sown now it makes a thick ferny mat that holds the surface through winter rain, and in spring you cut it down and leave it or add it to the heap as a green. We do not stock a wider green manure range, so for field beans, rye or clover you will need another supplier. Cardboard and compost do the same job, as set out in our no-dig gardening guide.