Improve Your Soil Using Wood Ash

, written by Benedict Vanheems gb flag

Spreading ash on garden soil

If you’ve recently had a bonfire, or like to warm yourself in front of a roaring fireplace or wood burner, then you’ll probably have lots of ash. Getting rid of it can be a bit of a nuisance, but it’s also a valuable source of nutrients, which makes it a great resource for the garden.

Wood Ash Nutrients

Wood ash is naturally high in potassium, which encourages flowering and fruiting. It also contains phosphorous as well as a catalog of micronutrients including manganese, iron, zinc and calcium.

Younger wood, such as twiggy prunings, produces ash with a higher concentration of nutrients than older wood. Similarly, ash from hardwoods like oak, maple and beech contain more nutrients than ashes of softwoods.

Ash from lumpwood charcoal is also good, but avoid using the ash from coal or treated timber, which could harm your soil and plants.

Wood ash can help make compost less acidic

Using Wood Ash in Compost

Wood ash is alkaline, so applying it to compost heaps helps to balance the tendency of compost to be more acidic. It also creates better conditions for composting worms, which will speed up decomposition. Compost that’s less acidic is perfect for mulching around vegetables.

Add wood ash little and often in thin layers. A few handfuls or one shovelful every six inches (15cm) of material is fine.

Using Wood Ash on Soil

Wood ash can play a useful role in correcting overly acidic soil. Most vegetables need a pH of 6.5 to 7.0, so if your soil’s below 6.5 sprinkle wood ash over the surface then rake or fork it in. Test your soil using an inexpensive test kit if you don’t already know its pH. Wood ash is particularly useful if you use lots of cattle manure in your garden, as this type of manure is very acidic.

Wood ash is approximately half as effective as lime in neutralizing acid. As a general rule, apply about two ounces of ash to every square yard (50-70g per square meter). Do this on a still day in winter and wear gloves to protect your hands.

Wood ash can be used around brassicas in place of lime

Using Wood Ash around Plants

Use the alkalinity of wood ash to improve soil for brassicas such as cabbage and Brussels sprouts. This is a great way to prevent club root, a common disease when soil’s too acidic. Apply it the winter before planting, or as a side dressing around actively growing plants.

Its high potassium content means wood ash is ideal to use around most fruit bushes, including currants and gooseberries, where it also helps wood to ripen, thereby improving hardiness, disease resistance and productivity. In fact, mix it into any soil used to grow fruiting vegetables, especially tomatoes.

Where Not to Use Wood Ash

Due to its alkalinity, wood ash shouldn’t be used around acid-loving plants such as blueberries and, to a lesser extent, raspberries. Don’t apply it to areas used to grow potatoes, as alkaline soil encourages potato scab. Avoid it coming into contact with seedlings too.

You’d need to add lots of wood ash to make your soil too alkaline for most crops. But for peace of mind re-test your soil’s pH every couple of years to check it doesn’t go above 7.5.

Store wood ash in a container with a close-fitting lid until you're ready to use it

How to Store Wood Ash

Finally, a word on storing wood ash. Because the nutrients it contains are soluble, you’ll need to keep it out of the rain so they don’t wash out. Containers with close-fitting lids are perfect for keeping ash dry until you’re ready to use it.

Wood ash can be a truly useful addition to the garden. If you use it too, please share your experiences in the comments section below.

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Show Comments


"I have planted radish two weeks apart x3. The radish have not made bulbs. My veg garden has plenty of organic compost (mostly from bokashi) and I have fertilsed with a general purpose organic fertiliser. The plants have now bolted . I live in the south western cape province of South Africa and we have NOT yet had real summer. What am I doing wrong?"
Theresa van der Byl on Thursday 6 December 2018
"Hi Theresa. This could be down to a number of factors. They need to be thinned out properly so that there is about 2 to 4 cm between each Radish. Also, if it has been particularly hot, this can sometimes encourage them to bolt. Keeping the radishes well watered in dry weather is essential too."
Ben Vanheems on Thursday 6 December 2018
"Thank you, great video which cleared up some concerns I had of over using wood ash. I have plenty from wood fire used in the winter. I've been putting ash in my compost with chicken manure and wood shavings from my chickens, but will now put around my veggies as well. Can I put it around fruit trees and roses?"
Karen Cane on Saturday 20 April 2019
"Yes, absolutely use it around your fruit trees and roses too. It will contribute towards better flowering and fruiting."
Ben Vanheems on Monday 22 April 2019
"I have been using wood ash for many years now. What I do is put a measured amount into a watering container ( typically a bucket for easy pouring ) and add water and mix the solution up. Then I pour this mixture directly around my plants. "
Richard Lyons on Wednesday 4 September 2019
"Thanks for sharing this Richard."
Ben Vanheems on Thursday 5 September 2019
"Hi, Thanks for the great videos. I live in the west of Ireland and burn turf ( know as peat in the UK ) on the fire, can I use this around my plants instead of wood ash? Patricia. "
Patricia on Saturday 5 October 2019
"Hi Patricia. Yes, turf/peat ash is fine to use in the garden, but mix it into the soil after applying. There is some scientific literature out there which links relatively high levels of lead and zinc in peat ash with the contamination of crop land on St Kilda in Scotland, which eventually lead to the evacuation of the main, inhabited island, Hirta. So I would advise caution and suggest you apply peat ash in moderation, saving the bulk of it for around flowering plants such as roses."
Ben Vanheems on Monday 7 October 2019
"Excellent video. Many thanks."
Phil Davies on Tuesday 2 June 2020
"I burn mostly wood but usually add some processed nuggets of coal type fuel into the mix - maybe 70/30% wood ash, coal type fuel. Does this mean my ash is unusable because of the coal content?"
JMW on Monday 3 August 2020
"I'm afraid it does mean you cannot use the ash. Coal ash can be damaging to the soil and plants, so I would dispose of it some other way. Pure wood ash is good though."
Ben Vanheems on Monday 3 August 2020
"I just recently purchased a compost barrel. The Instructions that came with the barrel said not to add wood ash to the compost as well as meats, bones , dairy or invasive plants. I understand all but the wood ash. Does anyone know why they would say this?"
Charlie on Tuesday 17 November 2020
"It may just be a precautionary statement. Pure wood ash - from clean, untreated wood that hasn't been painted or adulterated in any way - should give good, clean ash that can be added in (modest) amounts to the compost barrel. But there may be other reasons for not adding it I'm not aware of. Certainly any excess ash can be spread thinly onto beds and borders without causing any harm."
Ben Vanheems on Wednesday 18 November 2020
"I apparently have an invisible switch inside my brain that when triggered emits "feel good" hormones throughout my body. The triggering event is seeing, then participating with, people from every walk of life and DNA mix God has created; that are now joining together to freely help one another solve/improve common interests and goals. I am not naively wishing politicians, clergy, business leaders could do the same- but what a glorious world we ALL could walk in if "they" would try to emulate all of us rather than the inverse. I fervently hope you all recognize how special EVERY ONE of you are. To think- we were just trying to do better, to solve common problems by coming together over seeds and dirt..! Thank you all for allowing me to share an observation. Blessings, Kerry D"
Kerry D on Sunday 29 November 2020
"Gardening is a great unifier. Everyone becomes a better person when they garden!"
Ben Vanheems on Monday 30 November 2020
"People in the boreal forests tell me that the blueberries become very abundant the year after a fire. If the alkaline from the ashes should be a setback, what's going on?"
John Bartelt on Friday 4 December 2020
"Can you use the ash from smoking meat?"
Tammy on Saturday 5 December 2020
"Hi John. I've not heard this before, so can't really comment. Generally wood ash is quite alkaline, but perhaps the ash from the fire provides a sudden abundance of nutrients, while the soil itself remains acidic, as the wood ash from the fire may not be enough to significantly change the chemistry of what would be very acidic soil."
Ben Vanheems on Monday 7 December 2020
"Hi Tammy. Yes, I think this would be fine so long as the ash hasn't had lots of oily/fatty deposits dropped into it. But I imagine these will have burned off as the wood/shavings burned."
Ben Vanheems on Monday 7 December 2020
"Hello, I'm growing veg and fruit and olives in Southern Spain. Every year I get lots of ash from burning the branches after pruning olive trees. I usually use the wood char left from the fire in small quantities for my veggie garden but I have never used the ash because people say it is very acidic, nor I use it on my compost pile. I have never tested the ph of my soil. How do I go about testing ph? Is it good to use the wood char? Thank you for the video!"
Rosa on Thursday 17 December 2020
"Wood ash is very alkaline, so I think people are referring to its alkalinity. It certainly wouldn't be acid. This is why wood ash is good to use in the vegetable garden but not around acid-loving fruits like blueberry - as it will reduce acidity. I think it is fine to use in small amounts around the garden, as described in the article."
Ben Vanheems on Friday 18 December 2020
"I have used wood ash on my compost heap and round my apple tree and roses for many years now. I always wear gloves when doing this. One other thing it is very useful for is to put a small amount of wood ash on a slightly dampened cloth when cleaning the window of the wood burning stove. I have a sparkling window on my stove which is several years old, and have never needed to use anything else."
Cathy Bateman on Thursday 14 January 2021
"What an ingenious tip Cathy - thanks for sharing. :-)"
Ben Vanheems on Friday 15 January 2021
"There should be a warning at the top of this article about ash. After I read this article, I used ashes that I thought were fully extinguished. Twelve hours later, there were gusts of wind that ignited the smoldering embers near dried leaves. We had 20' flames, our hedge burned, and the fire fighters arrive. We are lucky our house or neighboring buildings around us didn't burn. Before composting ash, store ash in a metal container with a metal lid (no plastics) for over 4 days, so all the coals are 100% extinguished. We all want to do the right thing (i.e., compost) and not burn anything down in the process. "
Close Call in Cali on Saturday 13 February 2021
"Yes - that very sage advice. I always leave ashes where they are, in the fireplace, for at least a couple of days before emptying out. They should be cool enough to handle. Or pop them in a metal container as you suggest until they are completely cool. I'm very relieved to hear your house was okay in this instance."
Ben Vanheems on Saturday 13 February 2021
"I heard an old farmer who said he sprinkles wood ash on his lawn to deter the moles. I believe it’s actually deterring the Japanese beetle grubs. What are your thoughts?"
Rolande on Tuesday 1 June 2021
"Hi Rolande. I've not heard of that use of wood ash before. It wouldn't do any harm to the lawn in moderate doses, so it's certainly worth a try."
Ben Vanheems on Monday 7 June 2021
"we have a wood burner for heat, i always put it on my veg beds and in the compost but now thanks to the video i know not to put it on the bed where the spuds are going to grow. i always have potato scab, now i know why, thanks"
mel on Sunday 20 November 2022
"I love wood ash. I was reading about it this summer when I noticed my tomatoes had blossom-end rot. A TRAINED gardener next door tsk tsked and said the only thing to do was add agricultural lime and wait for next year because ag lime takes a long time to break down. But I’m a natural rebel so. I decided to try wood ash that I had in my outdoor fire circle that I wad worried about how to get rid of, and voila! within 10 days the new tomatoes were free of BER and the whole crop was saved. Love me some wood ashes!!! "
Jean on Monday 18 September 2023
"What a superb result Jean - great to be a rebel sometimes! :-)"
Ben Vanheems on Monday 18 September 2023

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