Can You Put Wood Ashes In Composting?

There are many composting tips and tricks, as well as a seemingly long list of things that you should and should not put in compost. Wood ashes are one of the items that you will find some controversy about as to how much and even if it should be added.

So, can you put wood ashes in composting? Yes, and wood ashes can sometimes be quite beneficial. Some plants and soil types, in particular, can be significantly improved by the addition of some wood ashes.

However, not all plants like wood ashes. This will depend on what soil you have, and there are a few other essential details. In some cases, wood ashes are better left out of the composting bins and away from your plants.

What Are Wood Ashes?

Wood ashes are the leftover gray ash that is left after burning wood. The dark grey or black remains are charcoal, not actual ashes. True ashes are nearly white in color, being a very light grey and naturally being a fine powder.

You can make your own wood ashes at home by simply burning things. This can be in a fireplace, fire pit, or a burning barrel. Keep the fire going until nothing is left but ashes. This can take several hours for even smaller items.

The simplest way to get your wood ashes is to clean them out of your fireplace periodically. This cleaning needs to be done anyway. You can then put the wood ashes in a bucket with a lid to be added to the compost pile as needed.

To get pure wood ashes, you can use something to sift the larger pieces out. However, this sifting is unnecessary, since the charcoal pieces that you may get with your wood ashes are also good for your plants.

This is because the charcoal that may be in the ashes is very porous. This porousness keeps plenty of oxygen in your compost pile, something that the microbes in it need. It also keeps the nutrients in the compost, preventing them from leaching out so that they will be available for your plants.

After making wood ashes, give the ashes at least a few hours to cool before adding it to your compost. Stirring the ashes every now and then can help them to cool completely so that you do not set your compost on fire when you add it.

Different Types Of Wood Ashes

One type of ashes is the leftovers from grilling and using charcoal. Charcoal used for grills often has chemical additives to it that can be harmful to your plants. Therefore, this type of ashes should never be used in composting.

Also, ashes from wood that have been chemically treated or painted on it should be avoided for the same reason. Simply put, anything with any chemicals in it should not have its ashes put into your compost. This includes furniture, plastic, stained wood, and anything else.

However, things besides wood can still be burnt and the ashes used as long as there are no chemicals involved. Ashes from straw, fabric that is pure cotton with no colors or additives, and other things are perfectly safe to use.

If in doubt, and especially if the compost will be used on plants you plan on eating, leave it out of the fire. However, if you are using your compost for ornamentals, you might can get by with ashes from things such as cardboard or paper that might have few chemicals in them.

Wood Ashes And Your Plants

As mentioned, wood ashes can be great for your plants. Ashes do not contain noteworthy amounts of nitrogen and will not, therefore, burn out your plants. What wood ashes does have is lime, calcium, potassium, magnesium, and other trace elements that your plants can benefit from.

However, wood ashes in large amounts can inhibit growth by restricting nutrients like iron. Apart from that, if wood ashes were given the same nutrient breakdown that fertilizers are, it would be 0-1-10. That is because wood ashes have 1% phosphorus and 10% potassium.

This is a great fertilizer for plants that love potassium; just be sure not to overdo it. Other ingredients, such as iron, manganese, boron, copper, and zinc, are also in wood ashes as well. Ashes are particularly high in calcium carbonate, which is a critical ingredient for many plants.

This part of wood ashes also raises the soil’s pH, depending in part on the type of wood used to make the ashes. This change in pH is why ashes are much better off in a compost, instead of applying them directly on plants.

Besides improving the soil health, adding wood ash compost around plants may be beneficial in repelling some types of insect pests, including slugs and snails. Just be careful putting it around seedlings, which can be sensitive to any form of compost.

If the soil where you live is highly alkaline, you should perhaps avoid adding any amount of wood ash that would raise the pH of your compost. If your soil needs added lime, you could simply use compost that has plenty of wood ashes in place of the lime.

How Much Wood Ashes To Apply

Because wood ashes do affect the pH of the soil, you should take this into consideration when deciding how much of the wood ashes to add. Different plants prefer different pH levels, after all, so think about the type of plants you will be putting the finished compost on.

When adding wood ashes, you should also take into consideration what else is going into the pile too. Most compost piles can have the tendency to get acidic, so adding something alkaline like wood ashes can help balance the pH better.

If you are composting for plants that love acidity, such as blueberries, rhododendrons, or azaleas, you should reconsider adding wood ash to your compost since it will raise the pH level. If the plants you wish to put the compost on prefer a higher pH, feel free to add more wood ashes.

You do not want the soil’s pH to swing too far in either direction since this will lock up the nutrients in the compost. However, most plants prefer a slightly acidic soil. Therefore, you should test your compost pH regularly.

Finally, you do not want to add too much of any one ingredient into your compost pile, whether wood ashes or something else. When it comes to your compost pile, wood ashes are a ‘brown’ material that must be balanced out by ‘green’ things.

A healthy compost should have approximately three times as much brown ingredients as green ingredients. Wood ashes, by itself, should never make up any more than 5% of your compost.

How To Add The Wood Ashes To Your Compost

First, you should test the pH of your compost pile to make sure that it is not already too alkaline. You can get a test kit for your pH from most garden centers, or you can send in a sample to be tested.

Next, you will need to pick a day that won’t be either wet or windy. This is because wood ashes are very fine and will easily make clouds of powder in the air. For this same reason, you should put on a face mask and goggles when dealing with ashes.

The tiny particles of ash, if inhaled, can be extremely irritating for your lungs. Not to mention that the particles can irritate your skin, so you should at least consider wearing gloves as well so that the ashes don’t get on your skin.

Use the wood ashes while you are adding layers to your compost. Place 3’ of your green layer and then your 9’ of brown layer, but don’t use any more than ⅛” of ash per brown layer that you add. Make sure that you turn your compost regularly to get everything well-mixed.

If your compost pile is ‘hot,’ indicating that it is busy breaking down into dirt, you can add the wood ashes and other things to the compost every month. However, if your compost pile is ‘cold,’ only add it once or twice per season at most.

Also, if you are putting your ashes into something like a tumbler (FYI – this is my favorite tumbler (Amazon Link)), make sure they have had time to cool. One of my neighbors melted part of his tumbler by placing the ashes in too soon. He’s lucky he didn’t start a small fire.

Final Notes

Composting your wood ashes is a convenient thing to do with the ashes from your fireplace or fire pit. Not only does composting get rid of the ashes, but it also turns them into something quite beneficial for your plants.

While composting your wood ashes is better for your garden overall, you can apply the wood ashes directly. This should be added only if the soil is very acidic and only in small amounts, but it can deter pests like slugs and snails.

However, never mix ashes with a nitrogen fertilizer since this can cause a chemical reaction that can release ammonia. You should also be aware of the fact that wood ashes can be very caustic, especially when mixed with water.