Using Wood Ashes in your Garden ( A Great Soil booster)

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Whether you have just had a small bonfire or a cookout, you are probably left with a pile of ashes that you just aren’t sure what to do with. Or maybe after a long winter you have a pile of wood ash from the fire place.

One idea you might have is using the ashes in your garden, but is this a good idea or one you should avoid? And is wood ash or charcoal better in your garden?

Instead of tossing wood ashes into the waste bin, they can be spread in the garden as they provide nutrients beneficial for growth. Commercial charcoal briquettes you would use for a barbecue likely contain chemicals like lighter fluid that can be harmful to your plants.

Because of this, the ash from these briquettes should never be used in the garden. Wood ash does contain a lot of good things your plants need, but moderation is key. If your soil already has high levels of certain minerals or nutrients adding more by sprinkling ash could overdose your plants.

For more in-depth information on using wood ash or charcoal in your garden continue reading this article.

Is charcoal the same as Ash?

Is ash and charcoal the same thing?

Ash Versus Charcoal

Ash is the dusty and flaky grey substance that remains of a wood fire in a fireplace or a wood-burning stove, whereas Charcoal is the chunky lightweight black pieces of a wood fire, these two substances are called ” Wood Ashes”

Many gardeners will add ash or charcoal to their gardens throughout the year.

The ash and charcoal act as a fertilizer or an amendment to the soil. A soil amendment is added to the soil in an effort to improve the ability of the soil, like water retention or drainage. Doing so creates a more ideal environment for the roots of plants in the garden.

Ash is more commonly thought of as a fertilizer while charcoal is classified as a soil amendment.  

The difference being that amendments are mixed into the soil to promote healthy plant growth.

They help to change the soil and make it better. Fertilizers are used to supply nutrients to the plants through the soil.

Wood ash from a fire pit or in home fire place can be used in the garden, in moderation to help provide nutrients or raise the pH if need be.

The ash from wood contains many nutrients that will benefit your plants, but moderation is the key. Too much and you could overdose your plants. Testing your soil to see what it needs first is a great starting point to adding any fertilizer, including wood ash. Remember to use well sourced wood ash in your garden.

Avoid using wood ash derived from trees grown in industrial areas. The soil could contain chemicals and heavy metals that the tree will absorb throughout its life. Treated wood should also not be burned to produce ash for garden use.

Charcoal is another option commonly used in gardens, but this might not be exactly the charcoal you are thinking of.

Charcoal briquettes used for grilling should never be used in your garden.

These briquettes usually contain chemicals like lighter fluid and adding them to your garden’s soil will only transfer those harmful chemicals to your plants.

The chemicals are unsafe for the plants and for people. The ash from this type of charcoal should not be directly applied to the garden or used in composting.

There is charcoal made specifically for horticultural uses. This is helpful in amending soil, making it better at retaining water. This charcoal, also referred to as biochar in the horticultural industry,  is available in pre-packaged packs from retailers.

Is Wood Ash Good For A Garden?

Charcoal ash can be beneficial for your garden, but you have to use the right charcoal and it has to be applied in the right amount.

Charcoal developed especially for horticulture use is available for purchase at garden centers. You cannot use ash left after a night of grilling. As we mentioned above, this charcoal will contain harmful chemicals.

Commercial charcoal used in horticulture is often beneficial when added to the soil. It has been found to increase the water-holding capacity in the soil, reduce soil density, improve soil structure, and reduce nutrient leaching in soil.

All of these benefits lead to healthier plans and an increase in crop growth.

If you don’t want to have to constantly be buying this charcoal, also referred to as biochar, you do have the option to buy or build a kiln that will allow you to create your own.  These will allow you to convert biomass into charcoal for application in your garden.

Biochar is often made from straw, coconut husks, yard waste, and even wooden pallets.

As with most things, proper application is key with charcoal.

Your soil might not need to be amended or maybe it will benefit greatly from an application. Do some research and testing before hand.

Some soils will not benefit from an application of biochar, while other soil types do. You should also consider the make up of the charcoal. Depending on what the biochar is made of, it will have different chemical make-ups.

What nutrients does wood ash contain?

Now that we have established that wood ash is good in your garden when used in moderation, you might wonder why it is good. What nutrients are found in wood ash that are helpful for plants?

Calcium will be the most prevalent nutrient found in almost any wood ash. Calcium is often used to raise the pH level in the soil in fields and gardens. One reason you should use ash in moderation especially if your plants are sensitive to certain pH levels.

In addition to calcium, wood ash contains potassium, phosphorus, magnesium, aluminum, and sodium. These nutrients are found in much lower levels than calcium.

Because these levels are so low, wood ash is classified as a low-grade fertilizer. The levels of sodium are high enough that it could do some damage to plants that are sensitive to salts.

You might also find other nutrients like boron, copper, sulfur and zinc are present in wood ash, but they will be in small amounts.

One nutrient wood ash does not contain is nitrogen. When the wood burns, it gives off nitrogen as well as sulfur.

This brings us to a real concern with using wood ash in gardens. Wood ash sometimes contains heavy metals including lead, cadmium, nickel and chromium. High levels of heavy metals cause health issues for humans and animals.

Using wood ash in recommended doses usually means you won’t have a problem with heavy metals if they are present in the ash.

The levels will be so low, you likely won’t have an issue. If you are concerned about the level of heavy metals in your ash, testing can be done to identify the exact make up of your ash. If levels are too high, you won’t be able to safely use the ash in your soil.

Using Wood Ash As A Fertilizer

Wood ash does contain a lot of good nutrients that can benefit your plants and your overall garden.  The calcium, potassium, magnesium, potassium and sulfur commonly found in wood ash, will benefit your plants as they grow and produce their crop.

These nutrients and others we discussed before are so important for the development of your plants. They need the nutrients to survive and thrive.

Other Wood Ash Uses In The Garden

Aside from providing vital nutrients, wood ash is also used to help with the pH in soils. Wood ash is commonly used as an alternative to applying lime to soil.

The carbonates in the wood ash neutralize acid in your soil and increase the pH, lowering the acidity levels.  Remember on the pH scale a 7 is neutral, less than 7 is acidic and over 7 up to 14, is basic.

Before applying the wood ash, it is best to get your soil tested so you know where the pH level is without any additions. This testing should be done every few years at the least, to ensure you providing your plants with what they need.

Most vegetables do best in soil that is slightly acidic, registering at a pH level between 6.5 and 6.8. If you run the test and find your soil is very acidic, applying wood ash is a great way to balance the acidity, but be sure you don’t add to much or you might get too basic.

If you are applying wood ash rather than lime, about four cups of ash will be a substitute for one pound of lime.

What to Avoid Doing With Wood Ashes

One of the most common mistakes people make with applying wood ash in their garden is overdoing it. If we sound like a broken record, it’s because this golden rule is so important to remember.

  • Do not over apply the wood ash in your soil. We cannot say this enough. Over applications will seriously mess with the pH in your soil potentially making it too basic for your plants.

  • Always look at the desired acidity of the plant where you are applying the wood ash and check your soil’s pH to see where you are before application.

A little research will save you a ton of frustration in the long run. There is nothing worse than seeing all your hard work ruined and plants killed by a simple over application. If your soil registers at a pH of 6.5 or 7 and up don’t add wood ash.

  • Avoid prolonged direct contact with wood ash.
  • Protective clothing like long pants, long-sleeved shirts, and gloves should be worn.
  • Additionally, goggles and a dust mask are also good ideas. These items will help reduce your exposure.

  • If you do apply wood ash, avoid leaving the ashes in piles or big clumps. When the ash is in these piles or clumps, the concentration of the salts may damage the roots of nearby plants.

Wood ash contains high levels of sodium, more commonly called salt. Most plants cannot tolerate a lot of salt. There are varying levels of salt tolerance in plants, most plants don’t want a lot of it. Think about dumping a ton of salt on your meal. Too much and you won’t be able to eat it.

Plants don’t like it either. Too much salt will draw water out of their roots, leaves or needles in the case of pine trees. The cells in the plant will be killed and the plant will suffer. Ultimately,  your plant will either die or become so weak it will be susceptible to other diseases.

Applications of wood ash are best done in winter or early spring before you have even planted anything. This will help better prepare the soil for when you do plant.

Wood ashes lose their effectiveness when they are wet. The nutrients quickly leach from the ash. If you are storing ash for later use, keep it somewhere dry and if you have already applied it, think about reapplying, but make sure you are leaving enough time in-between applications.

  • As a final tip, avoid using wood ash created by burning treated lumber, or wood that was located in an industrial area. Also do not use ash created from burning trash or plastics. Use wood that is naturally sourced so you know no chemicals have been introduced.

    This will ensure chemicals, toxins or high levels of nutrients you aren’t expecting to add are met introduced to your soil and your plants. This could have lasting effects on your soil and do a lot of damage to your garden.


The use of wood ash and charcoal is not a revolutionary idea. For hundreds of years, agriculturalists have used these products to help with the growth of their farms and gardens. Even thought this isn’t a new practice, it is new to many beginner gardeners.

Wood ash and charcoal made for horticultural practices are both beneficial to gardens because they add nutrients, help the soil structure and help with pH levels.

These soil amendments and fertilizers are commonly used because they are so helpful. Whether you are a pro gardener or trying a new hobby, after some soil testing, you might just find your garden can also benefit from the use of wood ash or charcoal.