Spreading wood ash across the garden is an old method that has been used for hundreds of years. It gives plants potassium and can help raise the pH of acidic soils. Traditionally, briquettes used in grilling food were nothing more than cinders of pure wood. Today, charcoal briquettes made in factories are mixed with many different substances that make them easier to light and help control the temperature and length of the burn. Grill briquette ash is full of harmful chemicals that should not be used in the garden or compost pile.
Even though charcoal briquettes are made from biodegradable wood and contain many trace minerals, they also contain a lot of impurities from the process of making them. Contemporary charcoal used in grills has many added ingredients that are designed to make the grill easy to light and control while cooking. Different brands of charcoal briquettes may contain different amounts of coal dust, starch, sodium nitrate, limestone, and borax. Often, sodium dioxide remains in the ashes as a result of combustion reactions. Once mixed with water, sodium dioxide may become sulfuric acid.
Ash from charcoal briquettes contains too many toxins and residues for use in the garden as a fertilizer. Do not put this ash in the compost pile because it will add dirt to the humus that will then be spread on top of the soil. It is possible to make a pile of charcoal ash, but plants nearby, like grass and weeds, will die from the high concentration of ash and salts. Because rain will wash the charcoal ash across the ground, it’s best to put barbecue briquette ash in a fireproof container and take it to a landfill or another safe, nonvegetated place to be thrown away.
You can use clean, dry wood chips or logs from a fire pit to fertilize your garden. When wood is burned, it turns into basic nutrients that plants can use, as long as it is not treated with a lighter fluid. Wood ash contains substantial amounts of calcium, potassium and phosphorus. These elements are initially bound in salt forms, so its important to scatter wood ash broadly and lightly. When wood ash gets wet, it can release salts that can burn the roots of plants because they are so high in salt. This is what happens when potassium hydroxide forms.
Scattering wood ash on a garden is not always necessary. If your garden soil already has a lot of potassium in it, adding wood ash every year before planting is more work than it’s worth. Also, wood ash can raise the pH of soil, so adding it to soil that is already alkaline makes it even more alkaline, which is usually bad for plants. Do not scatter wood ashes around plants that need an acid soil environment to stay healthy. To make acidic soils more neutral, wood ash can be added. This makes the soil better for growing many common vegetable crops.
Charcoal ashes may seem like a great natural fertilizer for your garden, but should you use them? There are some benefits to using charcoal ashes but also some potential downsides. This article will examine the pros and cons of using charcoal ashes on plants.
What are Charcoal Ashes?
Charcoal ashes are the powdery grey remnants left over after charcoal has been burned. They are primarily composed of minerals like calcium, potassium, and phosphorus that were present in the original wood or organic material used to make the charcoal.
Small amounts of charcoal may also remain in the ashes, though most of the carbon is burned off during combustion. The ash content varies depending on the type of wood and the temperature at which the charcoal was produced.
Charcoal briquettes in particular tend to have more chemical additives and less mineral content compared to lump charcoal made purely from wood.
Potential Benefits of Charcoal Ashes for Plants
There are some potential benefits to using charcoal ashes in your garden
-
Provides minerals: Charcoal ashes contain minerals like calcium, potassium, and phosphorus that plants need for healthy growth. This gives them some value as a fertilizer.
-
Increases pH: Charcoal ashes are alkaline, so adding them to acidic soils can help raise pH. This makes nutrients more available to plants.
-
May enhance soil structure: The minerals and charcoal fragments in ashes could improve water retention and aeration in sandy soils.
-
Suppresses plant diseases: There is some evidence that applying ashes may suppress certain soil-borne plant diseases.
-
Deters pests: Spreading a light layer of ashes around plants may help deter slugs, snails, and other crawling pests. The abrasive texture irritates them.
Potential Drawbacks of Charcoal Ashes for Plants
However, there are also some potential downsides to amending your soil with charcoal ashes:
-
Nutrients easily leach out: Unlike more stable organic matter, the nutrients in ashes can quickly leach out of soil with rain or watering. The benefits are very short-lived compared to compost.
-
Can alter soil pH too much: Excessive applications of ash can drastically change soil pH, harming plants that prefer acidic soils. It’s easy to overdo it.
-
May contain harmful residues: Charcoal briquettes and some lump charcoals contain chemical additives and fuel residues that could be harmful to plants.
-
Can damage plants if too concentrated: The salts, alkali, and trace metals present in ash can burn plant roots and leaves if too much is applied in one place.
-
Provides no organic matter: Unlike compost, ashes contain no organic matter or humus to improve soil texture, moisture retention, and nutrition.
Best Practices for Using Charcoal Ashes in Gardens
If you do choose to recycle charcoal ashes in your garden, follow these tips:
-
Test your soil’s pH first and only apply ashes if your soil is too acidic. Excess alkalinity can be just as harmful to plants as excess acidity.
-
Thoroughly mix any ashes into the top few inches of soil over a broad area. Never apply concentrated ashes directly into planting holes or beds.
-
Use ashes sparingly and intermittently to prevent salt buildup. Less is often more with wood ash fertilization.
-
Focus applications around heavy feeding plants like corn, potatoes, tomatoes, and fruit trees. Avoid ashes around acid-loving plants.
-
Stick to lump charcoal ashes if possible instead of briquettes, and avoid ashes from charcoals with lighter fluid or other chemicals.
-
Consider supplementing ashes with nitrogen fertilizers. Wood ashes are low in nitrogen, so pairing them with nitrogen sources helps balance plant nutrition.
-
Till ashes into soil in fall if possible, giving time for salts to disperse before spring planting. Apply lightly, only once every 2-3 years.
-
Water soil thoroughly after applying ashes to minimize alkalinity and salt buildup in localized areas.
-
Monitor how plants respond – discontinue ash applications if you notice signs of soil pH issues or plant damage.
The Bottom Line
While charcoal ashes certainly aren’t poisonous and may supply some nutrients, their benefits tend to be small and short-lived compared to organic matter like compost. Excessive use can harm soil biology and plant health.
Occasional, light applications to acidic soils low in minerals can be helpful, but a balanced organic fertilizer program is generally a better option. Take care not to overdo it with ashes. When in doubt, test soil changes and plant responses over time.
WOOD ASH & BIOCHAR in the Garden // BENEFITS & DANGERS
FAQ
Can I put charcoal ashes in my garden?
Does coal ash help plants grow?
Is too much charcoal bad for plants?
What plants like charcoal?
How to use charcoal ash in your garden?
The following are some of the most effective ways you can use charcoal ash in your garden. If you have a pest problem in your garden, you can use charcoal ash to solve it. Just sprinkle some ash around your plants to keep the pests at bay. You can also use a pest-killing spray using charcoal ash if you want.
What are the benefits of charcoal ash?
Provides essential nutrients – Charcoal ash contains potassium, calcium, and magnesium, which are all important for plant growth. Improves soil pH – Charcoal ash is highly alkaline, which can help raise the pH level of acidic soils.
Does charcoal ash affect plants?
Please remember that excess charcoal ash will alter soil pH causing it to become more alkaline. So it can affect plants that prefer acidic soil such as blueberries, strawberries, azaleas, etc. if you use too much. Is Kingsford Charcoal Ash Good For Plants?
Are charcoal ashes good for soil?
The short answer to this question is: “it depends.” Not all types of charcoal ashes are good for the soil and plants. In addition, there are certain situations when using ash can damage the fertility of the soil. We will explain this answer in detail below. What Is Charcoal Made Of?