Skip to main content

Winter Woodfires: Using wood ash

As you know, through winter we heat our home and cook using a woodstove, so we produce lots of wood ash as a result.  Our current woodstove has a very clever design where the ash tray can be pulled out and emptied easily, this makes cleaning much more pleasant than when you have to scoop out all the ash.  We have to clean out the ash tray every couple of days if we have the woodstove burning every day.

eight acres: how to use wood ash in the garden
 A bucket of wood ash
We don't see the ash as a waste product though.  Wood ash is all the mineral matter remaining from the wood that was burnt, so its great for adding minerals to garden soil.  It usually also contains some unburnt carbon (biochar).  I spread the ash through the garden and tip it into the compost as well.  Wood ash is good for chickens to dust bath with, so I put it in their nesting boxes with a layer of wood shavings.
Spreading wood ash on the garden - I just hose it into the soil
I thought it would be simple to find out the mineral composition of ash, but it took me a while to figure out why the elemental composition didn't add to 100%.  Then I realised the balance is oxygen, as all the elements are present as mineral oxides.  Anyway, the composition depends on species of wood, the part of the tree, the growing conditions AND the temperature of the fire, but roughly, its 30-60% calcium oxide, 20% potassium oxide, 10% magnesium oxide, 10% sulphur oxide, and small amounts of iron and sodium oxides, as well as trace minerals.  So wood ash is a good source of calcium and potassium, and some other minor minerals.  Both calcium and potassium and very important for healthy plants, so wood ash is a great way to return these minerals to the soil.

The clever ash tray on our wood stove
Two things to consider before you start spreading wood ash around:

1) make sure it is completely cold.  I spread ash directly from the woodstove onto dry mulch once and had to very quickly stamp out a fire, even though it didn't seem hot at the time, it was still very hot inside.  Its also best to use a metal bucket to store ashes, plenty of fires start from plastic buckets of ash melting through, and keep the bucket on concrete or dirt rather than wood or plastic.

2) test your soil pH as all those mineral oxides form hydroxides with water, which will increase soil pH.  Soil pH tends to decrease as calcium ions are leached, so usually it is safe to add wood ash to maintain calcium ions and a neutral pH (7), but if you have naturally high pH soil, then don't add wood ash.

Speaking of hydroxides, the other use for wood ash is to soak it in water to make lye for soap making.  This is the traditional method, and much more difficult that using purified sodium hydroxide (caustic soda) like we can do today.  I'm tempted to give it a go one day though.

How do you use your wood ash?


  1. I dig mine into the onion beds and add it to my home made liquid feeds (comfrey and nettle tea) for tomatoes and peppers to feed on as well as adding it to their mix that I plant them into. I never thought of letting the chickens have a dust bath in it.
    Thanks for the chemical composition of wood ash. I always wondered what I was putting on the soil.

    1. the potassium is great for your tomatoes, helps them to flower :)

  2. Hi Liz, I have been using mine in a similar way- apparently it is really good for citrus.It was interesting to hear about the chemical composition.I over did it in one of my beds though and threw the PH out , so that was really good advice about checking soil Ph .
    Always interesting reading over at your blogx

    1. the potassium is also great for the citrus!

  3. I spread it thinly over the garden once a year and the remainder goes on pasture. No problems with doing it this way for years now. but like you say, the fire needs to be out of it and you don't even want to set a metal bucket of it on anything that might burn. I find that if I can spread it on or after a rain it does well. Have a nice winter, we are getting into the heat of summer and I am actually installing steel flu liners for 2 more wood stoves and need to do maintenance on the main wood furnace.

  4. I give it to the chooks, in their dome, they are very happy to spread it around. It gives a nice boost to the soil, in combination with their manure, kitchen scraps and all the stock bones that they’ve buried then covered with some mulch. Makes a great start for planting the next lot of veggies and the fruit trees that border them.

    1. I need to get my chickens into the garden to do some work!

  5. Last 10 years we have central heating in our house. My dad is sick and we can't chop and store wood anymore. But when we had wood ash we used it to melt icy paths during the winter. Ash melts ice just like salt only it doesn't work so aggressive and animal paws don't get damaged.

    1. that's a great idea (not that we get ice or snow here, but useful for others!)

  6. Great post - top info. I use wood ash whenever I can. It is a great replacement for lime being alkaline. The garden loves it, the slugs and snails aren't so fussed. :)

    1. good point, got to love anything that keeps the slugs away!

  7. your post prompted me to look into wood ash and how it is used for soap making, sounds very time consuming but much better than using caustic soda definitely something to research further

  8. Great post, this will be a featured post, on the HomeAcre Hop on Thursday.
    Thanks for sharing!

  9. My ash goes into all the holes that the pesky four-legged children dig. After reading this may have to pop into the dust holes the chooks have dug.


Post a Comment

Thanks, I appreciate all your comments, suggestions and questions, but I don't always get time to reply right away. If you need me to reply personally to a question, please leave your email address in the comment or in your profile, or email me directly on eight.acres.liz at

Popular posts from this blog

Worm farm maintenance

I have had the worm farm for over a year now, and I have to say it’s the easiest and most convenient way I have found to make compost and to dispose of vege scraps and other organic waste. I have not had much success with putting everything in a compost bin, I find that the food scraps go all sloppy and don’t really compost properly. I have found that my current system works much better, all food scraps go to the worms and the compost bin is for weeds and manure. The worms are able to eat all our food scraps and convert it to compost and worm tea, and there is still plenty for the compost bin, but now its not full of sloppy food scraps. People often ask if its necessary or possible to have both a worm farm and a compost bin, and I think it actually works better for us.

The worm farm really requires very little maintenance.  All I have to do is tip in more food scraps every few days, drain the tea once a week or so, check that the top tray is damp (if not, tip in half a bucket of …

The new Eight Acres website is live!

Very soon this blogspot address will automatically redirect to the new Eight Acres site, but in the meantime, you can check it out here.  You will find all my soaps, ebooks and beeswax/honey products there, as well as the blog (needs a tidy up, but its all there!).  I will be gradually updating all my social media links and updating and sharing blog posts over the next few months.  I'm very excited to share this new website with you!

Getting started with chickens - Tanya from Lovely Greens

Sign up for my weekly email updates here, you will find out more about soap and our farmlife, straight to your inbox, never miss a post!  New soap website and shop opening soon....

Farmer Liz: You will remember Tanya from Lovely Greens from the first series, she lives on the Isle of Mann and added chickens to her garden about a year ago.  You can leave comments for this post on Tanya's blog.

How many chickens (and other fowl) do you keep, what breed and what do you use them for (meat, eggs, slug control etc)?
Tanya: Around the same time that we were initially thinking about having hens another friend beat us to the punch. She went to the local pet store and bought a flat-pack hen house and chicken run combo and found a local farmer who had dozens of semi-feral chickens running around his property. One night he pulled three down from the trees and my friend took them home in a pet carrier. She named them Miracel, Carmen, and Geraldine and though they’re probably related they were all…