Tony O’Neill, gardener and author of the popular “Composting Masterclass” and “Your First Vegetable Garden,” combines lifelong passion and expert knowledge to simplify the art of gardening. His mission? Helping you cultivate a thriving garden. More on Tony O’Neill
There are many ways to manage leaves in Fall. You could mulch them with a mulching mower, collect them with a mower, blow or rake them into heaps, or use a vac-blower to shred and collect them. Whatever way you choose, they’re a fabulous resource to use in the garden.
Leaves are the tree’s primary energy converters and heat regulators. Perennial trees shed their leaves annually. Shed leaves consist mainly of cellulose and lignin. Leaves with high lignin levels are slow to decompose.
Because leaves are high in cellulose and lignin, they are resistant to bacteria breakdown. Fungi do initial decomposition, with bacteria taking over later in the process.
This piece will look at how easy it is to improve the soil in your garden with that often discarded without a second thought – leaves.
What is Leaf Composting?
In gardening terms, leaf compost is creating an environment where microorganisms can flourish to compost leaves into the soil, benefitting matter from yard waste.
The leaves that fall to the ground have little value in their initial state. Low in carbon matter, high in decomposition-resistant materials, and a tendency to either mat or blow away, fall leaves have little value.
However, by adding a little magic in the form of nitrogen, uric acid, carbon, water, and oxygen, boom, you have a highly valued soil enhancer.
To make the magic quicker when gardening, try to prevent too much heat from escaping. However, leaf compost doesn’t get as hot as bacteria-driven decomposition processes.
While it is common to refer to the process as compost, the composted product is leaf mold. This is because fungi, and not bacteria, mainly do the breakdown.
How Do You Compost Leaves?
Like with all compost processes, there are five essential ingredients to compost leaves when gardening:
- Carbon for the microorganisms
- Nitrogen for the microorganisms
- Uric acid for the fungi. Interesting fact: uric acid causes gout and can be found at high levels in beer. Second, mushrooms are high in uric acid, only to baker’s yeast.
- Water increases the mobility of microorganisms and acts as an energy supply line. Water also helps regulate temperatures.
- Oxygen to help with the oxidation process of the carbon-releasing CO2
- Heat speeds up the process. Much of the heat is self-generated, and our role is to help prevent that generated heat from escaping. A study done by MIT showed a direct correlation between ambient temperature and decomposition rates.
In all compost processes, it is good to have as much surface space as is practically possible. If you make your leaves too fine, room for air (oxygen) movement is reduced. Balancing particle size and porosity is crucial in your compost pile.
Because the construction of leaves has evolved to balance weight and efficient light exposure, leaves are generally flat (less so with succulents). Their flat shape creates a mat of leaves stuck to each other when wet or to blow away when dry.
It’s a good idea to shred the leaves before you add them to your compost pile. I shred my leaves 4-times before they are fine enough. To shred leaves, you can use one of the following methods:
- Run over them with a lawnmower that has a catch-bag.
- Vacuum them up with a blower-vac – Toro has a good one.
- Put them through a shredder.
You’ll need the following to create a leaf mold pile:
- Lots of shredded leaves – enough to create a pile that is no less than a 3-foot cube.
- Some* moist soil – ideally, you want some soil taken from a wooded area
- Some* horse manure – good but not essential
- Some urine mixed with water – urine is rich in uric acid – a rich form of nitrogen. The mixture should be a 2-gallon bucket full.
- A bin that can contain a cubic meter of leaves. Look at my video on making leaf mold and see what I did.
- A couple of sheets of wet newspaper
*The some referred to above is about a heaped spade full – or half a 4-gallon plastic shopping bag
Making a Nitrogen-Rich Wetting Agent
To make a wetting agent loaded with nitrogen and microorganisms, you will need:
- A cotton bag or a commercial horticultural compost tea bag
- 5-cups of horse manure
- 5-cups of nutrient-rich soil from a wooded area
- A 2-gallon bucket filled with water and topped up with 2-cups of urine
Place the horse manure and soil in the compost tea bag and soak in the water/urine mix for 48 -hours if you have an air pump (like those used in fish tanks), pumping air into the mixture will speed up the diffusion and proliferation of microorganisms in the solution.
The end product is a nitrogen- and microorganisms-rich water solution that radically speeds up the decomposition process in the compost pile.
Make Incredible Compost (Leaf Mold)
- Start with a 6-inch layer of shredded leaves
- Drizzle the layer with the urine mixture – wetting enough that a single drop can be squeezed out – bo more, no less.
- Spread a thin layer of horse manure/soil mixture
- Cover with a wet sheet of newspaper
- Repeat the previous steps until all the shredded leaves are used up.
- End with a layer of shredded damp leaves. Use a board or rake to compress the pile.
If you have an old rug, covering your pile will help retain heat and speed up the composting process considerably. It could even reduce the time to 6 months! That is 25 percent of what it usually would take (24 months).
What Is best for composting?
Leaves with a low lignin content are ideal for making leaf mold. Plant matter such as needles, which contain a lot of lignin (a strong building block), has a narrower decay rate range than leafier plants, which have much less lignin and more nutrients that attract microbes. Lignin protects organic compounds from degradation by acting as a shield.
Lignon-reduced leaves (with higher calcium and nitrogen levels) include ash, cherry, elm, linden, and maple. In 6 months, these leaves will be completely decomposed.
Beech, birch, oak, hornbeam, and sweet chestnut are unsuitable leaves because they are high in lignin and low in nitrogen. Magnolia and Holly are two more plants that should be included in this list. A typical two-year breakdown period is required. Trees like oaks, beech, and sycamore with thick leaves that stick around for a long time have high lignin levels and might leach nitrogen out of my soil.
How Long Does It Take For Leaves To Compost?
Leaves vary in their decomposition times. The Long-term Intersite Decomposition Experiment Team (LIDET) study collected litter from 27 North and Central America locations, from the Alaskan tundra to Panamanian rainforests.
The research showed that leaves in warm and wet regions decomposed faster in the compost pile than in cold and dry areas. The type was also a determinant – needles (high-lignin) deteriorated much slower than leaves with low levels of lignin.
In nature, leaves take about two years to decompose. As discussed above, decomposition can be reduced to six months in controlled environments when gardening this way.
Do leaves compost quicker if shredded?
Leaves are composted by the activities of microorganisms – mainly fungi. Because these organisms are tiny, and their action is on the material’s surface, maximizing the surface area maximizes their activity.
Consider a cube in water. Like a die, cubes have six sides. Cutting that cube into quarters produces 4 x 6 = 24 sides, which gives us 18 new surfaces exposed to the water. Repeating that process of quartering will increase the exposed surfaces exponentially.
Similarly, shredding your leaves increases the exposed surface area, thus increasing the fungi’s activity on the leaves. As seen in the video above, I shred my leaves four times to get a well-crushed mass that reduces the compost time by 400% – from 24 months to six.
Another handy way to speed up your composting is to create a wetting agent made from beer. You have an effective compost Kickstarter by mixing a medium bottle of beer, a can of sugar-containing soda, and half a cup of ammonia with two gallons of water.
What leaves should not be composted?
The general rule of thumb, a non-scientific approach, is using thinner leaves. The following is a list of trees and shrubs whose foliage has thicker leaves and are higher in lignin content:
- Sweet Chestnut
- Beech (to a lesser extent)
These leaves have high lignin content and might leach nitrogen out of your soil before giving any back.
For interest’s sake: lignin in wood is extracted to make polymers for paints and adhesives—nasty stuff for your garden, a good alternative to petroleum.
While lignin is strongly associated with retarded decomposition rates, the leaves’ C: N ratio has also been researched and may hold a more vital link to their slow decomposition. Either way, thicker leaves, even in accelerated environments, decompose slower.
Autumn carries more gold in its pockets than all the other seasonsJim Bishop
Can This Organic Matter be Added to Soil?
Mold is a fantastic way to make incredible compost. It is a gold mine for gardeners. It has a high mineral content and can grow plants naturally without additional fertilizer.
Contrary to popular belief, mold is beneficial to your garden lawn. As a result of the tree roots extracting minerals deep underground and transporting them to the leaves, leaf mold contains many valuable trace minerals.
Mold is one of the best soil conditioners you’ll ever use, despite the negative connotations associated with the word “mold.” A single mold spore can hold five times its weight in water. That’s on par with peat moss, if not better. Because of this, leaf mold is an excellent mulch to use around the garden. When added to sandy or clay soils, soil structure and texture are greatly improved.
Microbes and other beneficial organisms like earthworms thrive in mold environments. As a result, your garden’s soil will be vibrant and alive.
There’s also the fact that it’s free! Don’t let the lack of leaves in your yard stop you from participating. People are always willing to let you drop off bags of leaves or let you rake some for them.
Find out by talking to your friends and family! If you don’t like cleaning up after the leaves in the fall, make friends with them.
It can be used as a mulch, a soil amendment, in containers and raised beds in place of peat moss, and in your compost bin as a brown matter.
When using it as a soil amendment, I turn mold into the soil to a spade depth. I use between 2 and 3 inches of mulch around plants, careful not to mulch up to the plant’s stem or base.
Is It Legal To Collect Leaves to Compost?
Generally speaking, you can collect as much as you want from the garden and parks in the U.S.A. Otherwise, everything else is strictly forbidden.
If you’re going to collect leaves from national parks, don’t. To learn more, visit this site – Principle 4: What You Find – No Trace Center (lnt.org) – leave the leaves.
From local municipal parks, first, check with the park’s manager. Some counties encourage composters to collect the leaves from parks; others do not. You must check with your local council – breaking the rules can be expensive.
There are no prohibitions on collecting leaves in your own (and friends’) gardens, however. Your leaves, your choice.
What Equipment Do I Need To Make Leaf Compost?
Some ways of shredding leaves are gathering them in low piles, going over them with a mower, or vacuuming them up with a blower/vac shredder.
Alternatively, you can get a new garden shredder. The benefit of a shredder is that it will reduce effort and the volume of leaves. An electric shredder allows you to produce one bag of shredded leaves from several bags of leaves.
An advantage is that shredded leaves compost so much faster. I shred my leaves fine. An electric shredder allows you to choose between coarse, medium, and fine shredding. Since most electric shredders come with a stand, you can fit a catchment bag to collect the shredded leaves.
You can use the same shredder to shred paper too, a handy additive to the composting processes.
A tarp is a handy gardener’s tool. You can use it to gather leaves rapidly, cover your compost pile to retain heat, and much more.
1-Ton Bulk Bag
These items are perfect for carrying large volumes. A one-ton bulk bag is another excellent investment I found helpful in cultivating leaf mold. The size is ideal – 35 x 35 inches square and 43 inches deep. They are airtight and will prevent the compost from losing heat. Woven polypropylene bags are also handy for collecting leaves.
I use scoops that fit on my hands, converting them into big plastic shovels. Once you’ve raked your leaves into piles, use these to scoop the leaves into one of your 1-ton bags – ready for shredding.
It is easier to rake damp leaves than dry leaves. It is much easier if you have a 30-inch broad leaf rake that is light to use. Rake in the direction of the wind to make it easier. Create multiple piles that you can gather with your hand scoops.
While I usually use a hose to wet my compost heaps, for my leaf compost/mold, I use one of the above wetting regimes. To spread the compost tea evenly, I like using a watering can.
Compost Tea Bags
A compost tea bag allows you to create compost tea without clogging your watering can’s sprinkler. The instructions for how to do this are shared above.
Leaf Composting and Leaf Mold – what’s the difference?
Composting is the controlled aerobic biological decomposition of organic matter into a stable, hummus-like product called compost. Molds are different in that the decomposition breakdown is primarily done by fungi – though bacteria are involved to a lesser degree.
Is Leaf Mold a Good Groundcover?
Leaf mold is highly hygroscopic (attracts and retains water). As a soil additive, this is a great benefit. As a ground cover, this may hinder roots from accessing moisture. That’s the long answer. This short answer is that leaf mold is better in the soil than in the ground.
Can I use Leaf Mold as Potting Soil?
Absolutely! Leaf mold is an excellent option for potting soil. It is rich in nutrients, active with microorganisms, and retains moisture excellently.
You can significantly improve the soil in your garden by composting leaves. Additionally, the process is effortless and straightforward. It makes what, for many, is a tedious chore into a productive process. For me, leaf composting has become essential to a healthy, productive garden. I believe once you start, the same will be true for you too.
Composted leaves are black gold, which is called this for a reason. Adding leaf compost to your soil will build its structure and water retention capacity and improve microbial activity. Make yours now!
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