Managing garden leaves

Using leaves in the garden

Every year, leaves are washed into our rivers and lakes. As they break down, they use up oxygen and release phosphorus and nitrogen. This isn't good for our waterways, especially since phosphorus feeds blue-green algae. So, it's important to stop leaves and other organic matter from washing into our stormwater drains. Leaves are welcome in your green bin and will be composted and used in projects around the city. Never rake leaves onto the road, even if a street-sweeping truck is scheduled. Leaves collected by street sweepers cannot be composted and end up in landfill.

Leaves are great in the garden because:

• they release nutrients that plants need when they break down
• they keep our garden soil insulated and protect plants from extreme weather
• they give the soil a boost when we mow our lawns, making it healthier.

There are many ways to use leaves at home to help your garden and protect our waterways.

Mowing them in

Instead of raking, you can mow leaves into your lawn. Wetting them lightly first can help them stick together so the mower can chop them up. There are special mulching mowers that can help if you have a lot of leaves. Finely chopped leaves soon become part of the soil, feeding the lawn.

Mulching with them

Mulch keeps soil moist, prevents extreme temperature changes, and it's great at stopping weeds. It also protects the soil from being blown or washed away. When you use leaves as mulch, you're also giving your soil extra nutrients. Over time, leaf mulch will become part of the soil, improving it more.

Digging them into soil

You can dig leaves straight into your garden soil to improve and protect it. This works best in autumn, so the leaves have time to break down before spring planting. Or you can let leaves break down into leaf mould before you dig them in – see ‘Storing them’, below.

Making compost piles or bins

Compost is a dark, crumbly, earth-smelling form of organic matter that makes soil healthier and helps plants grow. Leaves are high in carbon, which is an important compost ingredient. When making compost it's important to:

• choose the form of container that works for you – a bin or a pile
• include other compost, garden soil, manure, or compost activator to add a range of microbes
• keep the pile moist but not wet
• turn and mix the pile occasionally to get compost faster

Compost bins can be faster than piles as they keep the contents warmer. Any shape or style of bin can be effective – choose one that works for you and is easy to use. For stationary compost bins and piles, use a layering approach to build up your compost. For a tumbler bin, just include a mix of nitrogen and carbon-rich ingredients.

If you can't compost at home, you can put leaves in your green waste bin or drop them off at a recycling centre, where they will contribute to city composting.

Storing them in a leaf cage

When you have a lot of leaves, especially during autumn, you can store them for future use. Storing leaves is a very simple and effective way to prevent them from entering waterways. If you use them in compost, store them nearby and throw in a handful or two each time you add kitchen scraps. Or just leave them to break down over time, enhancing soil health by returning their nutrients to the soil as leaf mould. Leaf mould is a rich, dark, soil-like material that forms when leaves have broken down gradually.

Leaves can be stored in a simple wire cage, made with wooden or metal stakes and a roll of chicken wire or a wire mesh.

To make your own leaf cage:

• Choose a location that is easy to access, shady and sheltered from wind.
• Drive up to four stakes into the ground around your chosen area. Flexible chicken wire and larger cages need more stakes, while a small cage using a firm mesh can be made with just one stake to support it.
• Wrap or unroll the chicken wire around the stakes and secure it with wire or a few cable ties.
• Fill it up with leaves.

Lightly water the leaves from time to time to keep them moist but not soggy. Adding water and mixing the leaves will speed up the process. The leaf mould will be ready to use in 6 to 12 months. To harvest, partly detach part of the chicken wire from the cage and scoop out the leaf mould. Many gardeners use leaf mould as a natural fertiliser and soil improver, or as an ingredient in potting mix.