Build your own worm farm

Article originally published by: Kiwi Gardener

Years ago, I picked up a Wellington City Council flyer on worm farms. It proclaimed: “anyone can start a worm farm”. I spend a lot of time (a) gardening, (b) hanging out with worms and (c) building things (albeit in an amateur sort of fashion), but I confess I didn’t get around to building a worm farm until this year. My inspiration came from a friend who built her own small-space worm farm from three stacking plastic bins. I was very impressed by the simplicity of this system, and how easy it was to create, and how much the worms loved it!

Worms really are the most amazing creatures. It’s easy to forget they are busy processing soil, 24/7, right under our feet! A worm farm simply intensifies the worms’ activity, and managed properly, encourages them to produce nutrient-rich humus. Worm composting can be undertaken year round, and the great advantage is that it provides people who have limited space with an effective means of recycling their kitchen waste.

Worm compost is perfect to use with a small-space garden where plants are grown in containers. Small amounts of humus can be regularly harvested from the worm farm and added to the containers to maintain the health and vitality of the plants.

Feeding Your Worms

Tiger worms and red worms thrive on moist, organic material such as vegetable and fruit scraps and peelings, shredded paper towels, tea bags, coffee grounds, crushed egg shells and plate scrapings. Feed your worms in moderation once or twice a week, burying the food into the bedding to discourage odours and flies. Every now and then, add a handful of mature composted manure to your worm farm to provide a source of composting microorganisms.

These micro-organisms help to soften the food for the worms.

Worm farm maintenance

Check your worms every now and again to make sure they are moist enough. If the bedding feels a bit dry, gently sprinkle a little water under the newspaper. If it feels too soggy, leave the lid off the worm farm and let the bins dry out a bit (cover the bins with netting while you do this to protect the worms from hungry birds).

Picky eaters!

Feed in very small amounts: onions, garlic, citrus and spicy scraps. Feed just a sprinkle of grass clippings (too much and the clippings will heat up and kill the worms). Don’t feed meat scraps or fatty, oily foods. Worms will eat this in time but while you’re waiting, the foods will get smelly and attract pests.

Step 1

Source three stackable bins (the ones in the photo are from Mitre 10). Drill 15-20 drainage holes in the bottom of two of the bins. The third bin is the catching tray for the worm juice so don’t make holes in it.

Step 2


Gather together a variety of bedding materials for your worms. This can include shredded paper, egg cartons, corrugated cardboard, shredded newspaper, straw, corn husks, ½ a bucket of mature compost, ¾ of a bucket of loamy/sandy soil (worms need grit to grind their food).

Step 3


In a large container, make a worm salad by mixing together all the bedding materials.

Step 4


Spray the worm salad with a little water (worms like bedding material to be moist but not soaking wet).

Step 5


Arrange the worm salad in the two bins which have holes in their bases. Sprinkle over some extra loamy/sandy soil.

Step 6


Ask a friend or neighbour who composts if you can ferret about in their bin for some composting worms. You’re looking for stripy tiger worms (Eisenia fetida), and red worms (Lumbricus rubellus), also known as red wrigglers. If you don’t have a worm donor, you can source composting worms at Mitre 10.

Step 7


Feed your worms some kitchen scraps. Cover the scraps with a piece of dampened newspaper.

Step 8


Stack your bins one on top of the other with the juice-catcher at the bottom. Cover the top bin of the stack with a sturdy lid. Put a rock or brick on top of the lid to keep it in place.