Leaf Compost

When Autumn Leaves Start to Fall…


Now that leaves are falling, don’t waste them.  Gather them up and compost them.

Left to rot they will make a mess.  The may cause hard surfaces to become slippery or they may stain light coloured surfaces as they decompose.

You might be inclined to think they can be left to rot into grass and that they will act as a fertilizer.  It is true the leaves can make a great fertilizer – but it is not a good idea to leave them to rot on your lawn.  They take quite a while to break down and, in the meantime, they will block light from the grass causing die-back and bald patches. These will be colonized by moss and weeds.   So, give yourself a good upper-body workout and rake them up. If your lawn is too large (or if you are too lazy) to rake up the leaves,  you can use a leaf blower, or suck up the leaves by driving over them with a rotary lawn mower with the deck set to its highest setting.  An added advantage of using the mower is that the blades of the lawn mower will chop the leaves which should help speed up the composting process.

Once you’ve gathered them up don’t burn them or dump them.  Once properly composted they will be invaluable in the garden.  Most trees are deep-rooted, they absorb minerals from deep in the soil A good portion of these minerals go into the leaves.  Leaf compost may contain twice as  many minerals as farmyard manure.  The mineral content may include things like phosphorus, calcium, magnesium, and other trace elements.  Recycling fallen leaves can restore these trace elements to the soil, and it will also add humous.   Humous is any fibrous organic matter that improves the   structure of the soil.  Humous will help to break up and aerate heavy clay soils, making it easier to dig and more free draining .  This will make it easier for a wider range of plants to develop healthy root systems.  Humous will also prevent sandy soils from drying out too fast.  It will help to soak up rain and check evaporation.

Composting Leaves

Good compost comes from an appropriate mix of carbon and nitrogen rich materials.  Fallen leaves are carbon rich.  So, on their own, they can take a long time to break down and won’t make great compost.  There are two things you can do that to encourage faster composting and a better result.

  1. Shred the leaves. Large un-shredded leaves tend to blow away or mat down into a soggy mess.  It can take 2 or more years for them to decay.   If shredded they will compost much faster. If you don’t have a leaf shredder you can use a rotary mower to chop up the leaves.  Pile up leaves and run the mower back and forth over the pile.
  2. Add extra nitrogen. Fallen leaves don’t contain enough nitrogen to provide sufficient food for the bacteria that aid composting.  Adding a nitrogen source, such as some farmyard manure , will help to start the compost heating up.  A mixture of one part manure to four or five parts leaves should work fairly well.  If you compost in bags, you can experiment with different ratios to see what works best.  If you don’t have access to farmyard manure, dried nitrogen supplements like dried blood, fish or bone meal can be used as substitutes.  Add about two cups of dried natural nitrogen supplement to each wheelbarrow load of leaves.

One way to try composting your leaves is to use heavy duty plastic bags.  Shred the leaves, fill up the bags with shredded leaves, dampen with rain water, and 1 part nitrogen-rich material – such as grass clippings or green household waste for every 4 or 5 parts leaves.  If you forget to add some  “green” nitrogen-rich components to the bag, the carbon-rich leaves won’t have sufficient nitrogen to get the composting process started.  Mix well and compact everything down enough so that you are able to close the bag, seal the bags, puncture them a few times with a pitch fork and leave them in an out-of-the-way corner in your garden.   Tumbling the bags regularly over the winter will help to keep things mixed things up which may help speed up composting.  It can take up to two years for the leaves to break down into completely into a crumbly compost.

If you prefer to build a compost heap, then it is a good idea to add the material in layers. To compost leaves, start with a six-inch layer of leaves, preferably shredded. Then add a two-inch layer of other organic material that is higher in nitrogen than leaves, e.g. animal manure, green household waste, green weeds, grass clippings, etc.  The heap should be kept slightly damp but definitely not soggy. Cover it cover it with a heavy duty plastic sheet or old carpet to keep the warmth in, and prevent the heap from getting too wet or too dry.

You need to turn/churn any compost heap regularly with a pitch-fork – at least every three weeks or so – to keep everything from compacting down into soggy mat.  The more you churn the better.

Leaf mold is basically semi-composted leaves.  It is not as rich a fertilizer as fully composted leaves, but it’s easier to make and useful as mulch.  Make a cage or leaf bin using posts and fine chicken wire. Gather your leaves, dump them in the cage, wet them thoroughly and tamp them down.   Wet leaves have a slight acid reaction. If your soil is already acid, you might want to add a little ground limestone to the leaves before tamping them down.

Over one winter, leaves stored in a wire cage are unlikely to break down enough to form a good compost but, especially if they were finely chopped up to start with,  they should be decayed and broken up enough to be used as a mulch.  Leaf mold is very good at retaining moisture – so it’s a great mulch for dry areas.  Good  topsoil will hold maybe 60% of its weight, but leaf mold can retain over 300% of its weight in water. If left for several years leaf mold should,  eventually, break down into a black, crumbly humus.

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