Country Gardener

Widely regarded as the authority on gardening in the south west

Worming your way to great compost!

Elizabeth McCorquodale looks at the efficient and hugely popular method of turning kitchen waste into high quality compost with your own wormery

For those of us who don’t generate enough garden waste to feed a compost heap or have no space to put one, a wormery is a very efficient method of dealing with kitchen waste and garden debris and as a bonus it provides a free and renewable source of garden soil conditioner into the bargain.

A wormery can be as large or as small as you like –the size is only determined by how much waste you want to process and, unlike a compost heap, it doesn’t need to be put in a sunny spot to work efficiently. With the correct number of worms for the size of your wormery you will have usable compost in three to six months – a lot quicker than most ordinary compost heaps. 

Worms are tiny waste processing ‘factories’ and as they can eat about half their own body weight in waste each day and, as it is their poo that we are after, a wormery is obviously a very efficient waste processing plant. 

In the ‘wild’ worms come to the surface to collect leaves and other vegetation to feast upon and they do this at night to avoid the dangers of dehydration and predation.

Although worms don’t have eyes, they do have light sensors on their skin so can quickly determine if they are in light or dark. For this reason always cover the top of your wormery to create a dark environment so that they continue to inhabit the top of the bin where you put the new waste.

If the top of the bin is too light, too hot, too cold, too dry or too wet, the worms will have no choice but to burrow down, cover themselves with a protective layer of slime and wait it out until conditions improve.

A wormery can be made from wood, plastic or polystyrene and it can be as fancy or as simple as you wish, but the basic design is the same: at the bottom is an area where the leachate (or worm ‘juice’) can collect, with a hole or tap to allow it to drain away. On top of this are stacked a minimum of two more boxes. The top one is the working box which contains a shallow layer of worm bedding, the worms and the unprocessed waste and the middle box contains the processed waste – the worm compost.

When the middle tray is filled with worm compost it is emptied (to be used as a soil conditioner) and then replaced on top of the other trays to be used as the working tray. The floor of all the upper trays have holes in them that allow the worms to travel up to the top tray to feed

If you keep in mind the few essentials of a happy worm, turning your kitchen and garden waste into a rich and nutritious soil conditioner is a quick, simple and trouble-free process.

  • Begin with the right quantity of worms for the size of your wormery, otherwise the worms will be too preoccupied with breeding to process your waste.
  • Use a soil test meter to test the moisture levels and the pH level of your wormery. The pH should stay at about seven and the moisture in mid range. If it is too wet add tightly balled newspaper, shredded cardboard or dry organic matter such as coir, and if it is too dry gently sprinkle the surface with rain water and lay a few sheets of soaked newspaper over the top surface of the wormery. A light scattering of lime will rectify a wormery that has grown too acid.
  • Maintain a good balance of wet and dry ingredients at all times.
  • Scrunch up paper and tear up cardboard in order to introduce air into the heap.
  • Maintain your wormery at a temperature of 15’ to 25’ C. Colder or hotter than this will result in reduced worm activity and any extreme could result in the wholesale evacuation of your worm population as they make a dash for freedom, or worse, death of your  colony.
  • Locate your wormery out of direct sun and move it indoors (into a garage or shed) over the colder months.  Your worms will slow down but will still be moderately active through winter.
  • Your wormery should not be smelly. If it is it means that moisture levels are out of balance, or that the worms have more work to do than they can manage.
  • Worms have their likes and dislikes.

They aren’t all that keen on onions, garlic or on citrus fruits.

drilling holes in stacking wormery.JPGHow to construct a wormery

You will need:

Three or more stacking boxes made of wood, plastic or polystyrene, one with a lid. When stacked there should be a free space of at least four - six inches between the bottom of one box and the bottom of the next, and they should fit snugly together around the sides.

A water butt tap

Worm bedding (moistened coir or leaf mold)

500g worms

  1. Mark a place for the tap on the short end of the first box, as close to the bottom of the box as possible. Cut a hole and insert the tap. This box will be the sump and will collect the leachate or ‘worm tea’ as it filters out of the top boxes.
  2. Drill 15 - 20  5mm holes in the bottom of the other two boxes
  3. Stack one of these boxes on top of the sump box. Fill it with a couple of inches of worm bedding and your worms.
  4. Add kitchen waste and lay a dampened, folded newspaper over top, then cover with the lid.
  5. To begin with add only small amounts of food. As the worms acclimatise to their new home you can add more scraps and waste paper until you reach the maximum limit for the size of your wormery.
  6. When this box is full of processed waste and worm castings, place the third box on top of the second and begin to add food waste into this top box in the same way as before. The worms will make their way up through the holes into the top box. Once this box is full the middle box can be emptied of its processed compost and placed on top for the cycle to continue.   
  7. Empty the sump on a regular basis and use the leachate to fertilise your ornamental plants, diluted at the rate of one part leachate to 10 parts water. Don’t use leachate on the edible parts of any plant.


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