Update: More details on Giant Gippsland Earthworms are here.
Update: I made some mistakes here and corrected them in this post.
Earthworms are the natural recycling factory. Charles Darwin said
Earthworms are nature’s ploughshare.
My garden and compost bin are full of earthworms, which I love, but paradoxically I don’t usually like animals or plants that were introduced to an area by people. Earthworms are one such invasive species in Australia. Australia’s indigenous earthworms can be huge. The Giant Gippsland earthworm (Megascolides australis) has an entry in the Guinness World Records at 3m long (although they’re usually 80cm long). It is a vulnerable species, close to extinction, because of habitat destruction (its habitat was small to start with) and human disturbance. This picture shows a Giant Gippsland earthworm being handled, but you shouldn’t do this because they are very fragile and bruise easily.
If you want to enjoy the benefits of the smaller and more manageable earthworms (which don’t mind handling), worm farming (vermiculture) is a space saving alternative for people who don’t have a garden. You can put the container they live in on a porch, patio or balcony. The material produced which is rich in worm castings (their poo) needs to be used on plants, which is ideal if you have balcony pots for herbs and other small plants. But if you don’t grow anything you could give it to a neighbour who has a green thumb or a local community garden. Perth doesn’t have so many community gardens, but schools are now starting to set up gardens for students to learn about where their food comes from (and some schools have been doing this for years). City Farm in the city centre of Perth is one community garden, which anyone is welcome to visit and volunteer at.
A home for worms needs lots of air holes so they can breath and there are usually a number of trays. The worms start off at the bottom tray, with food (kitchen scraps) and when they’ve eaten all the food, you put the next lot of food in the second tray and they migrate up through holes between the trays. You can then remove the lower tray which is full of worm castings and put the castings wherever you need to grow things. I care for the earthworms in my compost bin by adding whatever organic material I have to hand and the worms live their lives. ie. I do nothing for them. They seem quite happy with this arrangement (and so am I). When I turn the pile and spread the composted part on the garden, it should be full of worm castings as well as those other composted bits, and earthworms too.
Food for earthworms can be whatever organic kitchen scraps you have (plant matter only). Despite No Impact Man saying citrus is fine, it is acidic, which earthworms don’t like, and Gardening Australia says
DON’T USE citrus or onions as worms dislike these.
I put onion scraps and sometimes lemon rinds in my compost bin and the worms probably just crawl away from them. If I had a worm farm, I’d steer clear of lemons and onions.
You can buy a worm farm (the only ones I’ve seen are made of plastic) or make your own out of an old bathtub, old plastic containers or a set of drawers. The ready made ones have a tap to collect the liquid worm castings.
Although Vanessa at Green as a Thistle blogged about making a composting unit, it’s actually a worm farm. She probably doesn’t want other organisms (macro or micro) taking up residence. In a compost bin the organic matter needs to cook to become compost. The anaerobic bacteria in the middle of the compost (where there’s no oxygen) generate high temperatures (up to 60ºC). Earthworms would cook too if they found themselves in this airless centre, but because they need oxygen to survive they stay at the top, bottom or edges of a compost pile. When I turn my compost they get spread all through the pile and quickly crawl back to the spots they like. The air holes of a worm farm ensure there’s always oxygen available and anaerobic bacteria can’t take up residence.
A compost bin (if sitting on the ground) will acquire earthworms over time which crawl up from the soil and enjoy the easy pickings. To stock a worm farm you have to buy a quantity of earthworms. Tiger worms or Red Wigglers (Eisenia fetida) and Indian Blues (Perionyx excavatus) all live happily together. Or you could dig in someone’s garden for the earthworms. You’d probably have to dig for quite a while to get enough worms and the garden’s owner might not want you stealing their worms.
The Compost Book by David & Yvonne Taylor (Reed, 1993)