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  • Writer's pictureJulie Smith

Why wormeries are a must have for food gardens

Updated: Sep 3, 2020

I am a firm believer in a self sufficient garden, and that means having a complete composting area that will include compost bins and at least one wormery.

What’s the difference between composting and using a wormery?

The process of composting uses bacteria to transform garden waste into humus, the glorious organic matter that comes out of your compost bin. In an efficient compost bin, the bacteria will grow in successions and raise the temperature of the bin, making it hot. Ideally you want to reach 80 degrees celsius ( it’s the golden temperature that will insure weed seeds can’t germinate), but in a small garden bin you are more likely to get to 60 degrees or so.

A wormery, as its name indicates, uses worms to transform food scraps into two main products: worm cast which is a dark rich material full of nutrients and soil life, and worm ‘tea’, a liquid that come out of the wormery and can be quite good for the garden too. Wormeries don’t get hot as worms will control the temperature of their environment.

So in short:

  • Compost bins deal with garden waste and can sometimes accommodate food waste. It gets hot as the bacteria that consume the waste turn it into humus.

  • Wormeries deal with food waste only, do not get hot, and produce worm cast and a liquid sometimes referred to as ‘worm tea’.

Tell me about the worms!

The worms you find in a wormery are cool. But they are not like your common garden worms (who are cool too by the way). They are worms from the Eisenia fetida family, which are especially adapted to consume decaying organic material. Contrary to your common garden earthworm, they tend to live in groups, and will reproduce to match the amount of food they find.

Like their garden wandering cousins, Eisenia worms are hermaphrodite- every worm has male and female organs. They will swap sperm with other worms and when they think the time is right, they will use the stored sperm to fertilise their eggs. When the worms are pregnant, the eggs will be located in the saddle, the white ring you might see on worms. When the eggs are close to hatch, the saddle will slide off the worm like a napkin ring on a napkin, and its edges will seal, making it look like a tiny lemon. The baby worm will then hatch and (contrary to us) is a fully fledged worm that knows what to do, where to go and how to survive without the help of its parents. I told you they were cool!

How does a wormery work?

The most efficient wormeries for gardeners that are looking at producing natural fertilisers are the one that allow you to harvest the worm cast, so I prefer the ones that have layers. The bottom of the wormery is the sump, where the liquid gets collected and you get the tap. The tap should ALWAYS STAY OPEN.

On the on top of the sump you get layers (when you start your wormery you use one, and you add them as your worms reproduce, up to 3 or 4 layers). Each layer has worm size holes at the bottom that allow the worm to travel between the layers. They tend to sleep and reproduce in the bottom layer, and feed in the top layer. The to layer is where you feed your worms.

What do worms eat?

Your wormery worms will consume food scraps, as well as corrugated cardboard. The cardboard also helps balance the pH of the wormery and stops it from being too wet. Rip all your delivery boxes in fist size chunks and add the same volume of cardboard as the volume of food scraps.

Your worms eat food waste, but they can be a bit picky - they won’t eat everything. So you need to follow a few simple rules when feeding your worms:

  • Feed mainly: food waste like vegetable peeling and discards, stems, tea bags, banana skin, cooked grains, bread, cardboard (yes, cardboard).

  • Feed a little bit: coffee ground, cooked meat and cheese

  • Avoid feeding: citrus peel (orange, lemon, tangerine etc. peel), onion family (leek, garlic, onion peel), fish, avocado skin

You also want to avoid feeding the worms a lot of one thing in a go: tonnes of fruit waste will make the wormery acidic and likely attract flies for example. Some wormery company will sell you food, which might help at the beginning, but really you don’t need it.

How to start your wormery

When you get your wormery, it generally comes with a voucher for worms. So you can prepare the wormery, read instructions and order the worms when you are ready to get started. Once ordered your worms will come in the post, in a bag, and will need to get straight in the wormery.

Place your wormery in a sheltered position and away from direct sunlight (it will cook it). In the winter, the wormery will benefit from being protected with bubble wrap or blankets to avoid freezing.

Initially, your wormery should be started with the sump (TAP OPEN), one tray and a lid. Put a layer of cardboard at the bottom of your tray (use the packaging of the wormery), and start feeding the worms on top, with a small amount of suitable food scraps (see list above), and the same volume of ripped corrugated cardboard. Add your worms. Then, if you can, add a bit of carpet or matting on top as worms aren’t fond of light and this will ensure the first tray is quite dark. Then close your tray. Then, use a cut milk bottle in a garden pot to catch the liquid coming off the tap.

When starting your wormery, feed it slowly and patiently while the worm population increases. You’ll probably have around a few hundreds worms in your wormery starter pack. But a mature, fully productive wormery has around 2 to 4 thousands. Your worm population will double in size every two to three months, so it may take up to 18 months until your wormery is at full capacity.

It’s better to add too little food than too much, particularly early on. If you add too much the food will go off and get smelly. In good conditions, worms can eat about half their body weight a day. In cooler weather (winter) it will be a lot less. You also want to feed your worms regularly- once a week a similar amount works well.

As your initial tray gets full and food waste is transformed in cast, you can add the next tray and start feeding the worms from the top tray, and so on until you reach three or four trays height. Your bottom tray(s) will be full of worm cast, your middle tray will be half worm cast half food waste, and your top tray is mostly recognisable food scraps.

How do I harvest and use the products of my wormery?

Wormeries produce a liquid: worm liquid or ‘worm tea’, and a soil-like material: worm cast.

Worm ‘tea’ is NOT to be drunk despite its name, and is made of a mix of liquid from the food waste you put in the wormery and excretion from the worms. It can be quite difficult to identify what it contains, but if it smells of nothing or simply earthy, it’s good to use and you can add it to your watering can until it colours the water. You can water your p[lants with worm tea every two weeks in the growing season, and more in the spring when you are getting things started. If your worm tea ever smells bad (rotten, and strong) then DO NOT use it, and check the troubleshooting section below as something might have gone wrong in your wormery.

Really what you want is the worm cast as it’s full of healthy soil bacteria, and will work wonders in your garden. You can use worm cast by mixing it into water, or by mixing it into soil.

To use worm cast in water, add a couple of handfuls of wormcast to a 10L watering can, mix with water, and you have an incredible feed! To get the cast, get to the bottom tray of your wormery, and take a handful of cast there. Check for worms in the handful and put the strays back in the wormery. Water all your hungry plan with your worm cast mix every other week during the growing season (especially all your cabbage, tomatoes, and heavy feeders). You can’t really use too much of it.

Wom cast can be used directly too: you can mix a small amount of worm cast with your compost when transplanting seedlings that need energy like your tomatoes and other heavy feeders. You can also add a few handfuls of worm cast at the bottom of a hole or trench before planting trees, roses or potatoes.

Worm cast is full of healthy soil bacteria and nutrients and is great for a lot of reasons:

  • Pathogens have more difficulty infecting plants because the potential infection sites are already dominated and occupied by beneficial microbes found in worm cast.

  • Nutrients and food in worm cast encourages good microorganisms to grow, which in turn will add nutrient to the soil in plant available form

  • Soil structure is improved, with more oxygen reaching into the roots and preventing toxin build-up in soil by anaerobic micro-organismes

  • Water retention in soil is improved

  • Depth of root grow is increased

  • Decomposition of dead organic material and toxins are increased through the high concentration of good microorganisms

Troubleshooting your wormery

A healthy wormery does not smell. It might have a couple of flies and pot worms, but very little. You will also easily find pregnant worms in a healthy wormery.

What to do if you find the following:

  • Small flies, a lot of pot worms (thin, thread like yellow worms): your wormery is too acidic and wet. Add more cardboard and add a layer of soil (compost or dug up garden soil) on top of your top layer to stop the flies laying eggs.

  • Ants everywhere: it’s too dry. Add more items from the ‘mainly’ list of what to feed worms.

  • No liquid coming out/ smelly: check the sump, the tap is probably clogged or closed (you want it OPEN at all times). Also don’t overfeed as too much food will rot and smell.

Where to get your wormery

As I said, I prefer wormeries with layers, with a sump and a tap. Wormcity sells a range of wormeries, but quite a few garden websites will offer wormeries nowadays. Some local authorities will offer discounts to residents buying wormeries as it significantly reduces food waste, check with yours.

Happy gardening!

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