Making my own potting compost

To make: 200L potting compost working out at £2.40 per 40L bag (garden centre price £6-£7, and my homemade version performs better!)

I used:

• the composted contents of one 220L beehive / dalek bin (started out in a 330L bin and was moved on twice as it reduced in volume)

• 2 tarpaulin sheets

• a rotary compost sieve (this sort but cheaper options may be available: www.diy.com/departments/rotary-soil-compost-sieve-screener/5060575103952_BQ.prd)

• a bucket

• the lid of a 330L compost bin

• 2 40L bags of commercial topsoil (I used "vegetable soil" as it was the cheapest option at £6 / bag, if you have spare topsoil in your garden it's fine to use that)

• empty compost bags which had been cleaned and disinfected

• a wheelbarrow

Step 1: Dry the contents of your compost bin. I spread tarpaulins on my lawn on a sunny day and spread the compost on top of them. It is very difficult to sieve wet compost. I leave it for a day or two to dry out.

Photo above shows equipment used for making my own potting compost

Step 2: Sieve the compost

Position your sieve in your wheelbarrow if it fits, alternatively put it on top of a garden bag or plastic sheet. Take about 1/2 bucket of unsieved compost from the tarpaulin. Tip it into the sieve and spread it around a bit. Start by rotating the handle slowly to avoid overspill and do not press down, at this point you're just breaking up any lumps. Once the compost is below the level of the paddles add a bit of downward pressure to encourage the rest to go through.

Inevitably some material won't go through, either because it's slow to compost (toss it onto the compost bin lid, you'll be putting this back into the 330L bin) or it isn't compostable e.g. the threads from a garden bag shown below, put these in your pocket ready to go in the dustbin, and pebble which I pile up then add to an area of gravel near my pond.

Step 3: when the wheelbarrow (or garden bag or top sheet) has about 3 half-buckets of compost in it mix in some of the top soil. I've got a lot of experience so can tell from the mixture how much to use - in this case the top soil was particularly dense and the compost particularly light so I used a ratio of about 1/3 topsoil to 2/3 compost. If you're just starting out a 1/2 and 1/2 mixture is generally fine. Even better, if you have any leaf mould use 1/2 compost, 1/2 topsoil and 1/2 leaf mould. Once each batch is mixed put it into the empty compost bags for storage.

The compost may look a little scruffy but it's really good, nutritious stuff. It can be used as it is, but if you're filling pots for ornamental plants you can always add a top level of commercial multipurpose compost to make them look prettier.

A note about specialist composts: yes, you can make your own ericaceous / alpine / cactus / bonsai etc. composts, there are plenty of recipes online, but you'll almost certainly need to buy most of the ingredients. Personally I don't use much of these and find it more economical to buy small ready-made bags of specialist compost rather than multiple bags of ingredients most of which are likely to go to waste.

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