Fall is a special time of year for us composters due to the incredible bounty of organic matter available at our finger tips! We’ve previously written about the value of pumpkins for worm composting, but an autumn resource even more readily available to anyone living in temperate regions of the world is undoubtedly fall leaves!
Dead, fallen leaves (unlike their green, living counterparts) are widely considered to be a composting “brown” - a highly valuable resource for helping to balance out the more nitrogen-rich wastes such as weeds, grass clippings and livestock manures in more typical outdoor systems.
With this fact in mind, it’s very easy for the average worm composter to assume that leaves will automatically be a great bedding material in a typical worm bin (since “brown” and “bedding” are often synonymous in vermicomposting circles).
Unfortunately, this is a situation that’s a little less cut and dried than you might think! 😉
Leaves as Bedding - The Main Challenges:
- Intact leaves have little to no water-holding capacity. Moisture just tends to run off their surface and pool at the bottom of a bin (or drain out if there are drainage holes).
- Leaves also mat together very readily, impeding airflow and further limiting the potential for any sort of balanced moisture distribution in a smaller system (water hitting the surface tends to run to the sides and down).
- The reduced airflow and poor moisture distribution tends to result in a much slower breakdown process as well (unless you have some “helper” organisms - a topic we will circle back to in a minute), so you can end up with big clumps of intact leaves that can last for extended periods of time.
- Leaves also tend to heat up a lot more easily than some other types of worm bedding (e.g. coco coir, shredded cardboard), which can lead to temperature spikes and dry zones, especially in larger bins.
Now, before you assume leaves shouldn’t even be added to a regular worm bin at all, let us assure you that there are a handful of ways you can use them much more effectively:
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Basic Fragmentation - While perhaps not the most practical option in a lot of cases, especially if you have a larger worm bin, it’s worth mentioning that any sort of fragmentation of the leaves, alone, can make a big difference. Smaller particles means more surface area for microbial colonization and pore space for moisture penetration (and retention) - both of which will help the leaves break down faster and just generally be a much more useful material in the system.
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Lawnmower (and Other Machine) Mulching - This is a much easier and faster option for fragmenting a lot of leaves at once. If you do use a mower, you get the added bonus of ending up with a mix containing grass clippings and other materials, which can further assist with the breakdown process (and offer more nutrition for the microbes and worms). NOTE: With these types of mixes, especially when a lot of grass clippings are mixed in, we recommend using them more as a food supplement than as a main habitat material in your system, since they will heat up readily and may release harmful gases like ammonia if too much is added at once.
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Mixing with Other Materials - This can be helpful even with fully intact leaves, but it’s even better suited as a partner strategy when using some type of fragmented leaves. When you mix leaves with bulky absorbent bedding materials like shredded cardboard you can effectively offset some of the limitations that leaves have (listed earlier), while showcasing what makes them such a great material for composting.
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Aging / Composting - Letting your leaves sit for any length of time in a moist, warm(ish) environment will naturally make them more useful as worm bin food/habitat material. Generally, the longer they sit the better - and if you let them break down for a very long time, you should end up with actual leaf mold, which can be an excellent “living material” for any type of composting system.
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Using Helper Organisms - Unlike our Red Wiggler friends, there are other composting ecosystem organisms literally designed to munch on tough “browns” like dead leaves. The stars of the show in this department are most likely isopods (aka “rolly pollies”, “wood lice” etc), with millipedes being worthy of an honorary mention. Isopods can both fragment and directly consume leaves - even dry, fully intact leaves - very easily, especially if you have a sizable population of them in your systems. If you’d like to learn more about this (somewhat under-the-radar) topic, be sure to check out our blog post, “Isopods - The Ultimate Partner for Your Composting Worms?”
- As a Cover Bedding - Some of the properties that make intact leaves less ideal as a main habitat material can actually be advantageous when using them as a cover bedding, especially in larger systems with plenty of airflow. A thick layer of leaves above your main worm composting zone can help retain moisture and also provide insulation when a system is sitting in a cooler environment.
Summing Up
There’s never been any doubt that fall leaves are an excellent resource for most types of outdoor composting, but it should be clear by this point that there are some nuances when it comes to using them effectively in smaller (especially enclosed) worm bins. The good news, though, is that if you use at least one or (ideally) more of the strategies outlined above, you may come to realize that fall leaves are one of Mother Nature’s ultimate gifts for vermicomposters! 🍁🍂
Helpful Related Resources
Fall - A Great Time to Get Your Backyard Composter Going!
Pumpkins - The Ultimate Fall Bounty for Your Worms
Setting Up Your GeoBin for Worm Composting Success
Next Level Backyard Composting - Fall Prep
What is Living Material?
Bedding - The Most Important Material in Your Worm Bin?
How to Feed Your Worms to Get The Best Results From Your Worm Bin
Isopods - The Ultimate Partner for Your Composting Worms?
Recommended Products
Living Material Plus
GeoBin
pH Buffer Grit
BioChar
Worm Boost
Urban Worm Bag
Lil’ Wiggler Lab