Photography: Are Media Syndication / Rebekah Robinson / Canva
Some say composting is a gardener’s most important job; it’s one of the best things you can do for both the planet and your garden. While there are many methods and theories about composting, the variety can make it seem complex, especially for beginner gardeners.
Compost is a natural way to recycle garden and kitchen waste, keeping it out of the landfill. The diverse range of beneficial soil organisms found in compost helps release nutrients and suppress plant diseases, leading to healthier, stronger plants. These same organisms also improve the structure of the soil, whether it’s clay or sandy, by aerating it and transforming it into a crumbly, soil-like mix. Compost also makes soil more friable, meaning it can retain moisture while still draining effectively.
What type of compost bin is best for your garden?
Before you buy or build a compost bin, consider your garden’s needs. If you have a large garden are grow plenty of vegetables, a larger compost bin – or even two – would be ideal. If you only have a few garden beds, an in-ground composter might suit your space better.
There are many composting methods, but in New Zealand, we are most familiar with hot composting, cold composting, and worm farms. Hot composting is faster and will kill weed seeds and diseases, but requires more effort. Cold composting is easier but takes longer, and you need to avoid adding weed seeds and diseased plant material.
Although you can create a compost heap virtually anywhere in the garden, a purpose-built compost bin is tidier, retains heat better, and makes it easier to control moisture levels. For hot composting to be successful, you’ll need a bin with a volume of around one cubic metre.
A well-fitting lid is vital to keep the rain and vermin out. As long as you don’t add cooked food, fats and meat, rats and mice are usually attracted more by the warmth of the compost than its contents. Bait traps nearby can help keep them under control. Bad smells shouldn’t be a problem if you compost correctly, though small flying insects are often attracted to the pile.
To make a healthy liquid fertiliser for potted plants, brew compost tea by diluting compost with water, then sieving it to remove the solids.
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Where to place your compost bin
Your compost should be close enough to the kitchen for regular deposits of scraps, but not so the bin is too close when entertaining outside. A sheltered, sunny spot is best.
What to add (and not add) to your compost
Every gardener has their recipe for making compost, but the basic rule is to add roughly even amounts of:
- Carbon material, including twigs, dry leaves, tree pruning, untreated sawdust, cardboard and other woody materials
- Soft, green stuff such as kitchen scraps, lawn clippings, weeds (without seeds), hedge clippings, green leaves and seaweed
- Organic material such as eggshells, tea leaves, coffee grounds, wool scraps, feathers and wood ash
Make sure materials are chopped up well and add thin layers of poultry or animal manure, blood and bone, lime or some existing compost. Some gardeners use leftover wine, beer, yoghurt or expired milk as compost activators. You can also sprinkle garden soil between layers.
Tips for speeding up decomposition:
What to avoid adding to your compost:
- Cooked food scraps, particularly dairy, fat or meat.
- Weed seedheads, diseased or infested material, or invasive plants.
The composting process
Once you have your compost bin, start by adding a layer of dry, carbon-rich material at the bottom. Then, gradually build alternating layers of green (nitrogen-rich) and brown (carbon-rich) material. Every couple of weeks, sprinkle in some animal manure or other compost activators. Mix the compost regularly with an aerator to ensure outer material moves inward and gets properly aerated.
Stop layering once your bin is full, and if you have a second bin, start adding new materials there. The compost should be ready within a few months, once it has transformed into a black, crumbly substance that looks and feels like rich, moist soil.
Now, spread your finished compost around your established garden beds and enjoy watching your plants thrive.
Compost bins for every garden
Compost Bin
Best for: Large households and gardens that will get through plenty of compost
A true favourite of many gardeners, the regular compost bin is a simple, effective solution for transforming organic waste into nutritious compost for your plants. Designed for backyard use, these bins are ideal for households wanting to reduce landfill waste while enriching the garden.
To use it, place the bin directly into soil or lawn to encourage drainage and access for beneficial microbes and worms. Begin by layering brown materials (dry leaves, shredded newspaper, cardboard, sticks) with green waste (fruit and veggie scraps, coffee grounds, lawn clippings). Continue to fill, and you’ll notice the material breaking down over time. Stir the contents every week or so with a compost aerator (such as this one from Gubba) to speed up decomposition – this will also reduce the odour. Avoid adding meat, bread and dairy to prevent pests.
Within a few months, you will have dark, crumbly compost ready for use.
Many gardeners choose to have two of these compost bins, so while one is breaking down waste, the other bin can be filled.
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Compost Tumbler
Best for: Medium to larger-sized gardens
A compost tumbler is a drum-like composter mounted on a stand with a crank handle, designed for easy rotation for quick aeration. To use it, layer your waste in a roughly 50:50 ratio of greens (kitchen waste) and browns (dry leaves, shredded paper). These tumblers are typically dual-chambered, so you load the waste into one compartment, and once full and decomposing, switch to the other. Turn the drum two or three times per week to introduce air and speed up the decomposing process.
These tumblers are a great option for gardens as the elevated, enclosed design helps deter pests, while the tumbling action reduces unpleasant odours. Overall, these bins are ideal for gardeners seeking fast, tidy and efficient composting with minimal fuss.
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Garden worm farm
Best for: Veggie and flower gardens that will thrive with additional nutrients
An outdoor worm farm is a super-efficient solution for turning kitchen scraps into both rich worm castings and liquid fertiliser – aka ‘worm tea’. Set your worm farm up on level ground in a sheltered, partially shaded spot. Add damp bedding such as coconut coir, shredded paper or cardboard, then introduce about one kilogram of tiger worms (these worms are best at breaking down organic material). Finally, add a small amount of kitchen scraps (avoiding meat, dairy and citrus) and spread it around evenly. Don’t add any more scraps until the food is almost gone.
As the worms break down the waste, nutrient-rich leachate drains into the bottom tray – the ‘worm tea’. This is incredibly strong, so dilute it with water before feeding it to your plants.
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In-Ground Composter
Best for: Smaller gardens, raised beds or garden beds
Ideal for smaller spaces, the in-ground composter quietly enriches surrounding soil, improving structure, moisture retention and microbial activity. These sit in the garden, with the top slightly flared above ground to collect kitchen scraps. Garden-dwelling worms will burrow into the composter’s feeding holes, processing the waste and infusing composted nutrients directly into the soil.
These worm towers are a low-maintenance, seamless, and eco-friendly method to fertilise the garden, with minimal fuss and maximum benefit.
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