Burning leaves is a popular way to get rid of this plentiful yard waste. Will burned leaves be a good source of free fertilizer?
Burned leaves can be used in the garden in plants that prefer alkaline soil, greens, garlic, and peas. Burned leaves and wood are high in potassium which can improve flowering, strengthen cell walls and improve the nutrition of your garden produce.
The richest wood ash fertilizer is made of a combination of wood, twigs, and leaves. White ashes contain more potassium than darker gray and black ash.
If you have burned leaves in your yard you want to collect them as soon as possible before they get wet and lose the potassium to the surrounding soil.
You can use burned leaves on your garden plants to fertilize the plants and deter some pests.
The practice of using ash in the garden is well documented in gardening for centuries. The original name for this fertilizer was potash.
Potash came from the practice of collecting ash from fires, adding water, and using the resulting mixture in the garden.
If you want to use your own ashes in your garden there is no need to add water to process the ash.
Simply sprinkle the ash around plants and immediately water them to get the ash dust off the leaves and get the potassium and other nutrients into the soil.
It can also be tilled into soil that is known to be overly acidic.
Store any ash in a dry location for later use if you have extra left over.
Add Burned Leaves to Compost
Burned leaves can also be added to compost with other materials. The ash will increase the PH in your compost pile.
This can be a good strategy if you have a lot of leaves and a small compost area.
Be sure to obey all local ordinances about open-air leaf burning and be courteous of your neighbors who may be bothered by the irritants that are released with open-air burning.
White ash contains more potassium, but the chunkier or darker ash may help aerate the soil and improve its condition over time.
The Problem With Burned Leaves In the Garden
While using this free fertilizer in your garden can improve flowering, strengthen cell walls, and improve the nutrition of your garden produce, it does have drawbacks.
There are some characteristics of ash that may be harmful to your plants.
Lye
Ash contains lye and if ash is added at too high of a rate to your soil lye can accumulate and cause burns on your plants.
Lye is produced when large amounts of ash get wet.
If you sprinkle ash on your garden beds you are unlikely to get harmful levels of lye, but if you are adding large amounts of ash to a compost pile you may end up with a build-up of lye.
Salts
When ash gets wet it produces lye and salts. These salts can burn your plants.
As with any fertilizer, be careful to avoid overuse.
Accelerants
If you used any accelerants like gasoline, lighter fluid, oil, or kerosene when burning wood or leaves do not use them in the garden.
Accelerants should not be necessary when burning leaves and they should not be used when preparing wood and leaves for use in fertilizer or compost.
Altering Soil PH
When you add ash to your soil it turns the soil alkaline so things like blueberries and potatoes prefer acidic soil and they should not be fertilized with potash.
Be sure to know your plants and only use ash on plants that prefer alkaline soil conditions.
Wood Ash Vs. Leaf Ash
Not all ash is equal. White ash contains more potassium than darker ash and wood from hardwoods has higher nutrients than softwoods.
Hardwoods
Hardwoods like oak and maple are slower growing and more densely composed. The ash from these trees contains more nutrients.
Adding twigs and debris from these trees to your leaf burning may improve the nutrition to the ashes.
Softwoods
Softwoods like pine grow quickly and the wood contains fewer nutrients for your plants.
It stands to reason that since leaves grow on both trees at the same rate the nutrition level in the leaves is very similar.
If you choose to burn yard debris to fertilize your garden use a mix of leaves, twigs, and larger pieces of wood to create the best blend. Remove them from the fire pit as soon as they are cool enough to handle and store them somewhere dry before use.
Do Not Burn Your Leaves
While there are benefits of using wood ash in your garden, there are plenty of reasons to avoid burning your leaves.
Some cities have ordinances against open-air burning. This can result in a visit from the fire department and a fine.
When you burn leaves you release irritants into the air that can be challenging for those with allergies and asthma. Neighbors who are dealing with these conditions will appreciate you handling your leaves in a different way.
Leaves make great composting material and they can be mixed with other materials like animal waste to create a rich soil amendment for your garden.
Many people burn leaves to reduce the amount of space they are taking up in your yard.
Composting will reduce the size of your leaf pile over the course of several months without burning.
Some towns and cities offer free composting services. Call your local waste management office and see where you can drop off your leaves to be composted.
You may even be able to get compost from your city to use when you need it.
Should I use burned leaves in my garden?
There are many benefits to using burned leaves as a fertilizer in your garden. The added potassium can improve yields and nutrition in your garden produce.
Burned leaves or any other ash should only be used on plants that enjoy a low PH soil. Greens like cabbage, spinach, collards, and kale benefit from this fertilizer, and plants like tomatoes, peppers, and dill also tolerate this type of fertilizer.
If you are able to burn leaves where you live it can be a good source of free fertilizer but consider composting leaves when that is an option.