While not the same black gold the Beverly Hillbillies discovered on their lot all those years ago, this black “gardener’s gold” can still help yield a rich bounty. Called leaf mold for the fungus that aids in the breakdown process, it’s the perfect way to sustainably reuse all those autumn leaves blanketing your yard. But what exactly is leaf mold and how do you make it? Read on to see just how easy it is.
What is leaf mold?
Not to be confused with the disease that infects tomato plants, the leaf mold we’re discussing here has everything to do with helping, rather than harming, plants of all kinds. Also known as leaf compost, leaf mold is basically just a pile of leaves left to sit for a year or so as fungi break it down, gradually decomposing the contents.
Best as a soil amendment, leaf mold is a cost-free way to boost the organic makeup of your soil, creating a healthier environment for flowers, shrubs, trees, and produce to grow. It works by helping improve water retention (especially in clay soils), enhancing soil structure, and attracting earthworms — the latter of which oxygenate soil, break down pollutants, and add to the nutrient mix.
Note: Since leaf mold doesn’t produce enough nutrients on its own, it doesn’t really help much in the way of soil fertilization. So, it’s recommended that you add regular compost or other organic fertilizer to make up for that.
Benefits of leaf mold
Besides acting as a soil conditioner, leaf mold also:
- Reduces erosion and stormwater runoff
- Improves soil drainage
- Keeps weeds at bay in garden beds
- Boosts soil aeration
- Recycles fall leaves
- Adds organic material to soil
- Improves disease-resistance in plants
- Regulates soil temperature
How to make leaf mold (in 3 easy steps)
Unlike its traditional compost cousin (a combo of kitchen scraps, grass clippings, and wood chips, in addition to leaves), which undergoes the quicker, hot composting method, leaf mold is made by cold composting. This method utilizes fungi to break down the matter instead of bacteria.
A much easier, albeit slower process (it can take one to two years to complete), leaf mold requires zero upkeep; no turning of the pile and no monitoring of its temperature. Here’s how to make leaf mold in three easy steps:
Step 1: Collect the leaves
Just about any deciduous leaves can be used to make leaf mold, but be sure the ones you’re using all have a similar decomposition timeline. If you’re using leaves that decompose quickly, your leaf mold can be ready in six to 12 months. If the leaves you’re using decompose slowly, you’re looking at closer to two years before your leaf mold is ready.
Technically, you can use leaves from evergreen and conifer trees, too, but the waxy covering they have causes them to take the longest to decompose. If you want a usable pile in a more reasonable amount of time, stick with deciduous leaves.
Deciduous leaves that decompose quickly include:
- beech
- oak
- hornbeam
- ash
- poplar
Deciduous leaves that decompose slowly include:
- sycamore
- chestnut
- walnut
- maple
- magnolia
Note: Shredding leaves with your lawn mower will help the decomposition process go even faster. Make sure you dampen (not soak) them, too. Since fungi is what breaks down organic matter in this cold composting process, moisture is a must. Another tip? Nitrogen can help speed up decomposition, so focus on collecting your leaves as soon as they fall from the tree. Those leaves have a higher nitrogen content than leaves that have been sitting in your yard for a week or more.
Step 2: Pile them up and let them sit
You can store your leaf mold pile in a compost bin or a trash bag. Or, you can use a leaf blower or a rake to guide them into a stand-alone pile on the side of your yard.
Compost bin
At your local garden center, a compost bin (or tumbler) can cost anywhere from $25 to almost $500. But, you can DIY one, too. To build your own, you’ll need chicken wire, wire ties, and wooden stakes:
- Cut the chicken wire, so it’s at least 3 feet wide.
- Roll it into a cylindrical shape, and connect each end with wire ties.
- Set the wire cylinder on the ground, and lodge at least two wooden stakes into the ground inside the wire to keep it standing up.
- Fill the bin with your pile of fall leaves.
Trash bag
Another option is to gather your leaves into large trash bags. To make this process go a little faster, use shredded leaves–– and, after tying off the plastic bags, poke a few holes in them to ensure proper airflow.
Stand-alone pile
Using a leaf blower or rake to gather your leaves into a stand-alone pile is the easiest of the three options. Literally, that’s the only actionable step. Gather them and leave them alone.
Typically, leaf mold needs to sit a year or two before it’s ready to use. But different variables–– the size of your leaf pile, the amount of moisture it contains, and the type, age, and size of the leaves themselves–– can decrease or increase that time a bit.
Step 3: Use the leaf mold
When your leaves have metamorphosed into a pile of mushy, crumbly, dark brown to black matter (aka humus), you’ll know your leaf mold is done.
Layer on 2 to 3 inches of leaf mold overtop your potting soil for trees, shrubs, and vegetable gardens. For flower beds, use 3 to 4 inches of leaf mold.
As mentioned earlier, this soil amendment can improve soil’s water-holding capacity, increase drainage of the soil surface, and safeguard plant roots from extreme temperatures, among other things.
FAQ about leaf mold
Also an all-natural soil amendment, peat moss is harvested from bogs in the U.S. and Canada. And while, like leaf mold, peat moss retains water, helps with soil aeration, and contains nutrients and good bacteria, it’s not good with drainage and is much more expensive.
Plus, if you’re an eco-conscious gardener, you’re more likely to choose leaf mold over peat moss. The latter can take up to 20 years just to grow 1 inch, so it’s not considered a renewable resource.
Technically, you can use whole leaves in your garden beds, but doing so can also cause carbon-heavy leaves and microbes in the soil to battle it out for nitrogen access. Nitrogen is essential to plant metabolism, chlorophyll creation, and plant structure, so if those levels dip too low, it can stunt plant growth.
When to call in the pros
Leaf compost is probably the easiest DIY yard project a homeowner can take on. All you have to do is gather your leaves in a pile and let them sit for a year or two. Once the leaf mold is ready to use, you can put it to work in your garden.
Then again, raking leaves is a lot of work, and if you just don’t want to be bothered, hire a lawn care pro near you to tackle the job on your behalf. They’ll corral the leaves in a designated spot for you to come back to months down the road. Or, you can hire a landscaping pro once the leaf mold is ready for use, and they’ll help install it into your flower beds, vegetable gardens, and around trees and shrubs.
Main Photo Credit: Joi Ito | Flickr | CC BY 2.0
