It’s that time of the year again. The coffee shops we shake down for their spent grinds are wafting pumpkin spice into the air. The psychos in our lives have already started celebrating Halloween.
Most importantly for us as worm farmers, the leaves are starting to fall off the trees. Fall is the perfect time to load up on free bedding material for the year. For us, money does fall off trees.
Leaves!
They are not all created equal. Some are poisonous, and we need to take precautions to avoid them. Others may have dangerous chemicals on them that can hurt our herd. Use this guide as a reference to avoid causing more harm than good with your rake this fall.
Attention New Wormers!
Are you new to worm farming? Do you want to create a solid foundation of knowledge? There is too much information online! Much of it contradicts itself. You're asking yourself, "Who can I trust?"
Captain Matt!
Captain Matt and the Wormpeople team created Learn to Worm for you. We put everything we have into this course, which simplifies the process and will help you become a successful worm farmer.
Now, let's talk about our fallen heroes.
Why Are Leaves Great for Worm Farming?
Leaves are an excellent source of carbon for our worm bin. Carbon serves as the bedding for our bin. See our Bedding Guide for a deep dive into the different bedding types and their role. Leaves are an excellent source of bedding for a few reasons:
- Leaves are free: For us, money does fall from trees. Some people will pay you to remove their leaves!
- Support a microbial environment: Decomposing leaves create an ideal habitat for microbes, our worms' favorite food.
- Enhance fungal and mycelium growth: Leaves promote a fungal-rich environment, encouraging mycelium development and boosting nutrient availability, particularly phosphate, which is tough for plants to absorb.
Safe Leaves for Worm Farming
While some leaves are toxic, plenty of safe options can keep your worms happy and healthy. Here's a list of typical safe leaves:
- Maple
- Ash
- Elm
- Beech
- Oak (though it’s slow to break down)
- Fruit tree leaves (except for cherry)
Why are these leaves safe?
These leaves decompose quickly, providing a steady carbon source while creating a balanced environment in your worm bin. They don’t contain harmful toxins; worms can break them down efficiently. Oak leaves, although safe, take longer to decompose, so it’s best to mix them with other faster-decomposing leaves to maintain good airflow and moisture balance in the bin.
What Leaves Should You Avoid?
Here is a complete list of toxic tree leaves, where they are found, and what they look like so you can avoid them.
1. Eucalyptus
Regions: Australia (native), North America (California), Europe (Mediterranean areas).
Where they are found: Native woodlands, reforestation efforts, parks, and landscapes in warm climates.
Toxic Compounds: Volatile oils (eucalyptol) are harmful to worms and other organisms.
2. Rhododendron and Azalea
Regions: North America, Europe (U.K., temperate regions), Australia (common ornamental).
Where they are found: Residential gardens, public parks, and landscaped areas.
Toxic Compounds: Grayanotoxins, which are harmful to worms, pets, and livestock.
3. Yew (Taxus species)
Regions: North America, Europe (especially U.K.), Australia (less common).
Where they are found: Gardens, cemeteries, parks, and used as formal hedges.
Toxic Compounds: Alkaloids, particularly taxine, are toxic to many animals, including worms.
4. Black Locust (Robinia pseudoacacia)
Regions: North America (eastern U.S.), Europe, Australia (less common).
Where they are found: Forests, urban areas, roadside planting, gardens.
Toxic Compounds: Robin and phytotoxins present in the leaves, bark, and seeds.
5. Black Walnut (Juglans nigra)
Regions: North America (eastern U.S.), Europe (less common), Australia (rare).
Where they are found: Native forests, parks, residential areas.
Toxic Compounds: Juglone, which is toxic to worms, plants, and soil microorganisms.
6. Red Maple (Acer rubrum)
Regions: North America (common in the eastern U.S.), Europe (less common), Australia (rare).
Where they are found: Streets, parks, woodlands, and residential gardens.
Toxic Compounds: Wilted leaves produce compounds that can form oxidants harmful to worms and animals (specifically horses).
7. Boxwood (Buxus species)
Regions: North America, Europe (common in formal gardens), Australia.
Where they are found: Formal hedging, residential gardens, parks, and ornamental landscapes.
Toxic Compounds: Alkaloids, particularly buxin, which can affect soil organisms.
8. Cherry Tree Leaves (Prunus species)
Regions: North America (common), Europe (common in temperate areas), Australia (common in gardens and orchards).
Where they are found: Orchards, wild areas, residential gardens.
Toxic Compounds: Cyanogenic glycosides (can release cyanide during decomposition).
9. Horse Chestnut (Aesculus hippocastanum)
Regions: North America (common decorative tree), Europe (very common in parks and streets), Australia (less common).
Where they are found: Streets, parks, gardens, used for shade and decorative purposes.
Toxic Compounds: Saponins (including aesculin) are toxic to many animals and worms.
10. Oleander
Regions: North America (California, Florida, Texas), Europe (Mediterranean regions), Australia (common in warmer climates).
Where they are found: Gardens, parks, roadside landscaping, and hedges.
Toxic Compounds: Oleandrin and neriine are highly toxic to worms, pets, and humans.
11. Mountain Laurel (Kalmia latifolia)
Regions: North America (eastern U.S., especially Appalachians), Europe (rare), Australia (rarely planted).
Where they are found: Woodlands, gardens, and parks.
Toxic Compounds: Grayanotoxins, similar to rhododendron, are harmful to worms and animals.
12. Laburnum (Golden Chain Tree)
Regions: North America (less common), Europe (very common in ornamental gardens), Australia (occasionally found in gardens).
Where they are found: Gardens and parks as a decorative tree.
Toxic Compounds: Cytisine, highly toxic to humans, pets, and worms.
The Hidden Danger: Chemical Residue on Leaves
Even if the leaves you collect are not inherently toxic, there’s another threat lurking—chemical residues. Leaves collected from orchards, commercial farms, or treated lawns may have been exposed to harmful pesticides, herbicides, or fungicides. These chemicals can build up in your worm bin and potentially harm your worms and the quality of the vermicompost.
Common Chemicals to Avoid:
- Neonicotinoids: These pesticides harm the nervous systems of worms and other soil organisms.
- Glyphosate: A widely used herbicide, residues can disrupt the microbial balance in your worm bin and harm your worms.
- Copper-based fungicides: Commonly used in fruit orchards, copper can accumulate in the compost and damage soil life, including worms.
Avoid Waxy or Leathery Leaves in Your Worm Bin
While some leaves may seem harmless, waxy or leathery leaves should be avoided in worm farming. The thick, shiny coating on these leaves makes them resistant to decomposition. This coating can create anaerobic pockets in your worm bin, which harms worms by reducing airflow and increasing moisture retention. Worms may also avoid waxy leaves because they take much longer to break down.
Examples of Waxy or Leathery Leaves to Avoid:
- Magnolia: These large, thick leaves have a leathery texture and take a long time to decompose, making them unsuitable for worm bins.
- Holly: Holly leaves are thorny and spiny, with a glossy, waxy coating that worms struggle to break down.
- Laurel: Found in hedges, laurel leaves are leathery and slow to break down, making them a poor choice for vermicomposting.
Whenever you encounter waxy or leathery leaves, it’s best to avoid them and choose softer, more easily decomposable leaves for your worm's bedding.
How to Safely Use Leaves in Your Worm Bin
A little preparation goes a long way when using leaves in your worm bin. Follow these steps to use leaves in your bin.
Steps to Prepare Leaves:
- Shred the leaves: This helps them break down faster, making them easier for worms to digest and providing better airflow in the bin.
- Let the leaves age: Let leaves partially decompose or compost before adding them to your bin. This reduces the risk of harmful compounds and makes the material more palatable to worms.
- Mix with nitrogen-rich materials: Combine your shredded leaves with food scraps or other nitrogen-rich materials to balance the carbon-to-nitrogen ratio, which is crucial for worm health.
- Test small batches: When introducing new types of leaves, add them in small amounts and monitor your worms. If you notice them avoiding the material or trying to escape, remove it immediately.
How to Avoid Chemical Exposure:
- Collect from untreated areas: Whenever possible, collect leaves from places where you know chemicals haven’t been used, such as public forests, parks, or your yard.
- Monitor worm behavior: After adding new leaves, watch your worms. If they seem distressed or inactive, it may indicate the presence of harmful substances.
Best Practices for Storing Leaves for Worm Bedding
Properly storing leaves provides a reliable bedding material for your worm bin all year. Here’s how to store leaves effectively:
- Airflow is Key: Whether you're using bags, bins, or outdoor piles, good ventilation prevents mold. Using large garbage bags, stand them upright and open the tops for airflow.
- Keep Leaves Dry: Dry the leaves before storing them to avoid mold, rot, or unwanted pests. Fresh fallen leaves are best because they are dry and do not have bugs.
- Storage Options:
- Breathable bags (like burlap or mesh): These are ideal for airflow and can be stored indoors or outdoors.
- Plastic bins: Use bins with ventilation holes to avoid trapping moisture.
- Outdoor piles: You can store leaves in an outdoor pile, but cover them with a tarp to prevent them from getting too wet while still allowing some air circulation.
You cannot prevent other critters from inhabiting an outdoor storage pile. Check out our worm bin pest guide to learn friend from foe.
Worm People Conversations
Here are a few fun conversations about leaves from the Worm People forum. Not a member? Sign Up. Remember, when you first join, do as our worms do– Dig around and get settled. Use the search function to see if your question has already been answered.
Chad asked a great question about storing leaves and using them instead of cardboard. Following this guide will help you store them properly, and yes, we recommend you add them as you feed to maintain a 50:1 carbon ratio. Refer to our Worm Food Guide and Worm Bin Bedding Guide for more information about C:N ratios.
This is an excellent thread with a ton of information about collecting leaves in your community. You all are dropping a lot of wisdom in this conversation. Thanks Elizabeth, Chad, George, Lauri, Brooke, Luke, Robert, Kevin, and Rexx. You make the Worm People community the best place on the internet!
Trick or Treat
You can keep your worms safe and happy by choosing suitable leaves and taking precautions to avoid toxic or chemically treated materials. Whether using tried-and-true safe leaves like maple or elm or avoiding toxic options like black walnut, your fall leaf collection can provide an excellent, free resource for your worm farm. Just remember to check your leaves, prep them properly, and keep an eye on your herd!
Happy worm farming, and remember—sometimes money does fall off trees!
