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.

Read on or watch our video to discover when and where to use it...

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

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