Angus StewartIn-ground worm farms for the time-poor gardener

How do you find the time to maintain a compost heap when you don’t even have the time to do the fun stuff in your garden? This is an increasing situation I am seeing with gardeners in urban areas. There is also a lack of space for the traditional compost heap. I commonly see people throwing their kitchen scraps in the general rubbish bin and the reason always given is that composting is just too hard and too much work.

My DIY in-ground worm farm ready to dig in

My DIY in-ground worm farm ready to dig in

I have spent years thinking and experimenting with composting and how to tailor methods that will suit every gardener’s situation and I think there is a perfect solution for the time poor gardener – the in-ground worm farm. The simplest composting solution of all is to just dig a hole in the soil and bury your kitchen scraps, and the natural earthworm population breeds up and consumes what you have buried. However, the advantage of an in-ground worm farm is that you can create a micro environment that allows you to introduce worms that are better adapted to rapid feeding such as tiger and red worms, using them to speed up the composting process.

Compost worms

Compost worms

The advantages of in ground worm farms are numerous:

  • Unlike above ground worm farms the body of the worm farm is insulated from temperature and moisture fluctuations leading to a more stable environment for the worms that can save them from extreme heat and cold.
  • Unlike above ground worm farms and most alternative composting methods the nutrients and humus created goes straight into the ground either by washing into the soil below or by the worms carrying it out through the holes in the worm farm that are below soil level.
  • As the worms move in and out of the worm farm they cultivate and aerate your soil, largely alleviating the need to cultivate.
  • An in ground worm farm never needs cleaning out because if it ever reaches capacity you simply extract it from the soil and move it to a new position. Any uncomposted material left behind will continue to break down without any further intervention. It is a good idea to transfer some of the worm rich material under the surface (that will also likely contain worm eggs) to the re-installed worm farm in its new position.
  • Apart from adding the food they are virtually maintenance free as the worms can carry most of the organic matter out into the soil around them thereby creating a ‘self-cleaning’ system
How to make a DIY drainage pipe in-ground worm farm

How to make a DIY drainage pipe in-ground worm farm

An in ground worm farm is a very simple thing to create and can be easily constructed from an old bucket or piece of PVC drainage pipe. The most important thing is to use material that has a reasonably large diameter. Ideally, a pipe should be at least 100mm (4 inches) in diameter to achieve a critical mass of organic matter that does not dry out too quickly, something that helps sustain worm populations in my observations. An old bucket would also generally be of suitable diameter but you may need to check that it will not perish or crack up if you want reasonable longevity for your worm farm.

Make a lid for your DIY drainage pipe in-ground worm farm

Make a lid for your DIY drainage pipe in-ground worm farm

An old length of PVC drain pipe is an ideal material to use as it is formulated to last a long time and the wider the better within reason, with a diameter of 150mm (6 inches) being close to optimal in my experience. A cylindrical shape for your in ground worm farm works well terms of being able to easily extract it from the soil in order to be able to move it to different positions around the garden.

The tube down which you put all your kitchen scraps in the in ground worm farm

The tube down which you put all your kitchen scraps in the in ground worm farm

Cut horizontal slots into the pipe in the below-ground section, using a large drill to make initial holes and then a hacksaw. This lets the worms can move freely in and out. Make a lid for the top of the unit to keep out vermin – mine has aerating holes covered with some fly wire and a top handle so it’s quick and easy to open and close, or you could just use a securely fastened wire cover. In my DIY in-ground worm farm, the bottom buried section is about 20cm (8 inches) tall and the above-ground section into which I put all the kitchen scraps and paper/straw is about 30cm (12 inches) high.

Worm Feast unit before assembly

Worm Feast unit before assembly

There are commercially available in ground units available such as the Worm Feast unit. This is a useful product that is easy to assemble and install and works extremely well, particularly as a waste disposal unit. When fully assembled it resembles a science fiction hybrid somewhere between a Darth Vader mask and a Dr Who dalek, but don’t let this put you off, as once it is buried in the soil ready to go all you see is a small black lid. The lid is removed to add all your kitchen scraps, but make sure you also add some sort of fibrous material such as chopped straw occasionally to add some aeration to the pile inside the Worm Feast.

All you can see is the black lid of the Worm Feast when it's buried

All you can see is the black lid of the Worm Feast when it’s buried

It does, however, have a couple of limitations in my opinion. Firstly, the inverted cone shape makes it very difficult to extract from the soil when you want to move it; and secondly, it has a lack of holes or slots along the outside which means that the worms and nutrients tend to only move out the bottom of the unit rather than the sides. The latter issue can be remedied by drilling or grinding some extra holes or slots in the side before it is installed.

Conical shape of the Worm Feast

Conical shape of the Worm Feast

Whether you use a commercial unit or one you construct yourself, the in ground worm farm is an extremely simple and ultra-effective composting solution that will dramatically reduce your organic waste stream if you are currently disposing of it in the bin. The only word of extra advice I would give is to ensure that you add some fibrous material such as shredded cardboard or chopped straw to your kitchen scraps to ensure the worms have adequate oxygen to breathe. You will be pleasantly surprised by the extra growth in your garden, and can also take pride in diverting all that carbon from going into landfill (and creating the greenhouse gas methane) to your soil, where it is doing a power of good for your plants. This is one of the simplest and best things you can do every single day to help the environment at an individual level.

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Angus Stewart

About Angus Stewart

Gardening Australia TV presenter, author of 'Creating an Australian Garden', 'Australian Plants for Year-round Colour' and 'Let's Propagate', garden travel guide, native plant specialist and breeder. Central Coast, NSW. Find out lots more about native plants at Gardening with Angus.

3 thoughts on “In-ground worm farms for the time-poor gardener

  1. Anne King on said:

    Brilliant! I’m off to check out my old pipe and bucket collection. Plan to put is several down the middle of the raised bed veg garden. Existing worm farm is kept in the garage, which seems to cope with hot days, but a problem if away from home for several weeks as it is not accessible for anyone else to add more food.

  2. I started doing this a couple of years ago with a couple of buckets, and feel that the soil is so much better. Somehow the red tiger worms also migrated into my compost tumbler, and that is pumping along because of them.

  3. I love your design, Angus! My next garden is likely to be very small but I can see this working well. I had thought I’d stop composting. Thanks for showing us how it can be done.

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