Does Wood Ash Kill Grass? A Definitive Guide

Wood ash is the powdery residue left out after the combustion of wood for burning wood in the fireplace, bonfire, or from any industrial plant. The wood ash is made of 25% calcium carbonate, which helps to increase the alkalinity of the soil.

It is also used as fertilizer, containing less than 10% potash, 1% phosphate, and minute traces of micronutrients copper, iron, zinc, and manganese. It also has minute traces of heavy metals nickel, cadmium, lead, and chromium. However, wood ash has no traces of nitrogen in it. But, does wood ash kill grass?

In short, wood ash doesn’t have that much of a ability to kill grass.

Does wood ash kill grass? What you need to know

Does wood ash kill grass?

In general, wood ash does not have the capability to kill grass. However, the application process of wood ash depends on the survival of grass on your lawn. Applying wood ash properly is essential, or it would eventually kill the grass.

Since it has lots of micronutrients and calcium, it’s great for the fertility of the soil and is used as fertilizer. Since it is highly alkaline with a pH of 9 and above, it is also used to increase the soil’s pH. 

Therefore, you must be cautious when applying wood ash to your lawn. Because it is the significant nature of the soil to be slightly acidic, so when you apply wood ash to adjust the pH of the soil, be very careful with the quantity.

It is best to check the pH of the soil first. Or else, if the soil is already alkaline and wood ash is added, it would kill the grass of your lawn. 

How to Apply Wood Ash on Grass?

Wood ash should be applied very carefully and cautiously on your lawn to prevent the grass from getting killed. 

How to Apply Wood Ash on Grass
  • Since wood ash is alkaline, it is mandatory to test the pH of the soil first before applying wood ash. Based on the test results, you can decide on the quantity of wood ash to be applied. 
  • It is strongly advised not to apply wood ash when seeding or overseeding the lawn. Because the presence of salt in ash would be too harsh for the seedlings to withstand and eventually die, so it is best to apply it before seeding or overseeding or once the turfs come out. 
  • Never apply wood ash that is still burning or hot. Make sure it is cooled before it is spread over the lawn. 
  • Sieve the wood ash thoroughly before it is applied, and remove the large chunk of coals and unburned wood. 
  • Wear protective gear before applying wood ash. It is best to wear gloves, a respiratory kit, goggles, and safety glasses. It is not good to breathe in ash. 
  • Apply wood ash on a calm day. Moist the lawn first, as it will prevent the particles from drifting away. Once you wear all the protective gear, spread the wood ash in small quantities gently. 
  • Ash should be spread on the lawn in even quantities and avoid any lumps in it. 
  • Make sure you do not apply any types of nitrogen fertilizer within one month of application of wood ash, as it is detrimental to the growth and development of the grass. 
  • It is always best to check the wood ash before it is spread over the lawn. It should not have any type of chemical contaminants, or else it will get mixed with the soil and destroy the grass. 
  • Be very sure with the quantity you apply. Generally, 10-15 pounds of wood ash is appropriate for 1000 sq ft of lawn. 

What does wood ash kill?

Wood ash, if not applied properly, kills grass. However, it is a great chemical to kill moss and weeds like spear thistle, Japanese knotweed, and kudzu from your lawn and garden. Moss and weeds prefer neutral or acidic soil, and wood ash being alkaline, is capable enough to kill them.

What does wood ash kill

They also kill and prevent slugs and snails from attacking your garden and lawn. They are also used to melt the ice that gets accumulated in your garden. Wood ash also kills parasites such as mites, ticks, fleas, and lice. They are also spread in the garden to kill pests like aphids and cutworms. 

Other Articles About Killing Grass: Does Antifreeze Kill Grass | How To kill Orchard Grass In Your Lawn

frequently asked questions (fAQs)

Will grass grow over ash?

Yes, grass can grow after applying wood ash onto the lawn. Wood ash comes from the firepit for the lawn and the soil of the garden. However, the pH of the soil needs to be checked first before applying wood ash to the grass. If the quantity is not correct, instead of growing more grass, it will result in killing the grass.

What is the best thing to do with fireplace ashes?

Fireplace ashes should not be thrown away. It is best to amend the soil’s pH and boost the grass’s growth in your lawn. Due to the presence of nutrients in wood ash, it is also beneficial for plants. You can also make compost tea by mixing wood ash with indoor compost, which is great for the growth of plants and lawns.

Are Ashes good lawn fertilizer?

Wood ash is considered to be a great lawn fertilizer that helps in the growth of the lush green grass of the lawn. The presence of potassium is highly favorable for the growth of lawn grass. The best is the alkaline nature of the ash helps raise the pH of the lawn’s soil and works better than limestone as it is easily soluble in water.

Is fire pit ashes good for grass?

Yes, wood ash is extremely good for lawn grass. Wood ash develops the overall quality of the soil. It also helps to boost the health of the grass due to the presence of potassium in wood ash and helps the soil to thrive in better grass. The presence of macronutrients in wood ash improves the growth and development of the grassroots lawn. 

Which plants love wood ash?

Apart from lawn grass, wood ash is also great for the growth of certain plants. They are garlic, onion, chives, leeks, lettuce, asparagus, and stone-fruit trees. Flowering plants like hydrangea, lavender, roses, and citrus thrive very well when wood ash is mixed with the soil.  


Wood ash should be applied very carefully when applied to lawn grass. When wood ash is applied in appropriate quantity, it helps the lawn grass to thrive properly. However, if it is not used in proper quantity, it would result in killing the grass of your lawn. Wood ash is already alkaline, so it is better to test the soil’s pH level.

Based on the soil’s pH level, the quantity of wood ash is decided and needs to be applied to the soil. Wood ash should be applied to the soil before seeding or overseeding or once the turf grass comes out and moist the soil before applying wood ash. Wood ash is also used to kill moss and weeds from the garden. 

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