How to Use Ashes As Fertilizer

Last Updated: December 15, 2022 Approved

You can use ashes from your wood-burning fireplace or brush pile to enrich your garden. Wood ashes contain most of the essential nutrients plants need to thrive. Knowing how to use ashes as fertilizer lets you recycle waste while helping to grow a luscious garden.

Steps

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Use wood ashes as a soil amendment in the early spring while the soil is dry and before the plant life has begun to actively grow.
- Nearly all plants benefit from the potash content of wood ashes.^{[1]
  X
  Trustworthy Source
  Royal Horticultural Society
  Leading gardening charity in the U.K. providing resources for identifying, growing and caring for flowers and other plants
  Go to source} Other components of the ashes are beneficial to the soil and plant growth as well.
- Because the wood ashes act as a liming agent, they reduce the acidity of the soil.^{[2]
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  Research source} Plants that prefer acidic soil such as blueberries, azaleas or rhododendrons will not thrive if wood ashes are applied.
Leaving the ashes in concentrated piles could cause too much of a salt build-up in areas of the soil that could potentially harm your plants.

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The ashes help break down the organic materials as they compost.
Sprinkled lightly throughout the garden bed, wood ashes repel maggots, aphids, slugs, snails, and cutworms.^{[3]
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Research source} Reapply the ashes after heavy rains.
Otherwise they're liable to blow away before they have a chance to settle into the soil.
7
Use caution when using ashes in the garden.^{[4]
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Research source}
- The ashes contain a good amount of lye which is a caustic agent. For this reason, refrain from placing them on young tender plants. Wear gloves when handling the ashes. Use a mask to avoid breathing in the residue and protect your eyes with sunglasses or goggles.
- Avoid using ashes from cardboard, coal or painted wood. These substances contain chemicals that can be harmful to your plants.
- Monitor your soil to be sure it hasn't become too alkaline. Use a soil testing kit to check the PH levels or take a soil sample to your county extension office lab to be evaluated.^{[5]
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  Research source} Alkaline soil will need sulfur added to it.
Hardwoods will make 3 times the amount of ash per cord of wood than soft woods.

Community Q&A

Question

Can I use ash for a yellow rose plant?

Community Answer

No, you should never give ashes to rose plants because they prefer acidic soil. If you use ashes for roses, they may die in the alkaline soil.
Question

Is paper ash good for plants and shrubs?

Community Answer

It will be better if you'll use decayed organic matters like leaves or manure, used to improve soil structure and provide nutrients.
Question

Does boiling water remove fluoride?

William Shaw

Community Answer

It is very unlikely that boiling water would remove fluoride from the soil, and cold water would be cheaper. Adding a diluted solution of calcium chloride would effectively remove any ionic fluoride because calcium fluoride is virtually insoluble in water.

Warnings

Avoid mixing wood ashes with fertilizer containing nitrogen. Hazardous ammonia gas could result.

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Never apply wood ashes to potatoes as they promote potato scab.^{[6]
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Royal Horticultural Society
Leading gardening charity in the U.K. providing resources for identifying, growing and caring for flowers and other plants
Go to source}

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