Understanding Wood Ash in the Garden – It’s Not All Good


You may have heard that wood ash is a great addition in your garden. But what if I told you that in my garden wood ash is one of the worst things I can add, but at the same time it might be one of the best things that you could add to your garden. Join me as I discuss wood ash. Hi, I’m Gardener Scott and wood ash is one of the most misunderstood additives and amendments that you might use in your garden. It’s almost universally recommended as something that’s very good for your soil and something you should be doing in your garden. But that’s not the complete truth because for many of us it really isn’t something that we should be adding to the soil, to the garden, or any part of our landscape. Wood ash is quite simply the ashes left over from burning wood, like in my fire pit. At the end of the winter you may be left with a lot of ash from your fireplace, from your wood-burning stove, or maybe from a fire pit. And because it’s so prevalent in so much of the world, you see a lot of videos and there’s a lot of books and there’s a lot of blogs from gardeners who recommend taking this wood ash and using it in your garden and there is good reason for this because wood ash is very high in many of the nutrients that plants need. It’s got phosphorus. It’s got a huge amounts of potassium. It’s got calcium and magnesium. And on the surface, it really looks like it is something that you should be adding to your soil. And that’s why so many gardeners recommend it. So for something that has so much nutritive value why is it a bad thing? Well, it’s because wood ash is very alkaline. Now for many parts of the world that have acidic soil adding some wood ash to the soil will actually raise the pH closer to neutral, which is great for most plants. And that’s one reason why you see it recommended so much because a lot of those authors and a lot those gardeners are gardening in areas with acidic soil and by adding wood ash they’re actually making their soil and the pH in the soil much better for plants. But for me and many other gardeners who grow in areas with very alkaline soil, this makes a bad situation worse because we’re already dealing with high pH values that might be right on the border for plants and their ability to absorb nutrients. And nutrient absorption, within the plants, begins to fall once pH gets outside that normal neutral range. So if I increase the alkalinity in my soil beyond where it already is, I may actually be harming the plants to the point that they would die. So I can’t add this to my soil. You need to understand your own pH. Do you have an acid soil or do you have an alkaline soil? Because that is critical in determining whether you use wood ash in your garden. Also, there are many plants, acid-loving plants, that do not want the pH raised at all. Plants like blueberries and azaleas and rhododendrons. They need an acidic soil and by adding wood ash you’re really inhibiting their growth. And even plants like raspberries, that I have a lot of in my garden, they prefer it slightly acidic and it’s harder to grow in my soil that’s alkaline already. This would do no good for the plants that I like to grow. I highly recommend getting a soil test done for your garden so that you have a really good idea of your pH and the nutritive value of your soil. I’ll be doing a video showing how to do that in the weeks ahead. When it’s complete I’ll put a link right here. With a soil test it takes the guesswork out of the benefit of wood ash. It’s one of those things that almost every video you look at discussing wood ash recommends the application. But like I already pointed out you can make a bad situation worse. So avoid the guesswork and get an answer to what your pH is before you consider the use of wood ash. There are many gardeners that refer to the potassium we use in our garden as potash. That’s the word that’s come down through the centuries to describe the ash at the bottom of the pot after the wood was burned and for centuries it’s been used as a source of potassium. It is very caustic. It’s also used to make homemade lye to use in making homemade soap. So if you do choose to use wood ash in your garden I recommend spreading it on a calm day, wearing some eye protection, and wearing gloves. Because in large amounts it can definitely harm your skin and be very hazardous for your eyes. If you have acidic soil, then yes, you should definitely be spreading wood ash in your garden, if you’ve got a good source because of your own fireplace or fire pit or wood-burning stove. I would caution, however, that you only use ash from a natural wood. Don’t use charcoal briquettes. Don’t use one of those formed logs that you might use in a fireplace. And definitely don’t use the ash from treated lumber. But if it’s a natural wood that you’ve been burning, collect it and you can spread it throughout the landscape. It’s particularly good on lawns that have an acidic soil underneath them. Wood ash is very high in calcium carbonate and it can be used as a substitute for lime. So if you’re already in the practice of spreading lime on your lawn or anyplace else in your garden, transition to wood ash. You will need to use about twice as much ash as you would lime and you would spread it about two and a half pounds per hundred square feet. But if you burn a lot of fires, you’ve got a free resource at your fingertips, and you can really benefit the plants that you’re growing. For those of us with high pH soils there is one way we can use wood ash in our garden and that’s by adding it to a compost pile. The magic of a hot compost pile is that it tends to neutralize the pH values within the pile over a period of time and so even though this wood ash might have a high pH it eventually buffers within the compost pile and all these nutrients get added to that finished compost. There is no nitrogen in the potash or wood ash but there’s enough of the phosphorus and the potassium and all of the other nutrients that it really can make for a better compost. Another option if you have none of those pH concerns is to make ash tea and put that around your plants. It’s like a compost tea. You basically just take a bag of ashes and soak them in a bucket of water. After a few days you use that water to fertilize your plants. Because the potash is a 0-1-3 fertilizer, if you choose to use it as such. Wood ash really can be good for your garden. But please don’t blindly follow all of those other gardeners out there that say you must use it or you should use it in your garden until you know your pH. Because if you’re a gardener like me, following that advice it could really be catastrophic for my plants. If you’ve used wood ash and had success with it, I’d love to hear about that below and on the other side if you’ve used wood ash and it didn’t turn out so well tell me about that too. In fact if you have any comments or questions about using potash, wood ash, in your garden I’d like to hear about it. If you’d like to see more Gardener Scott videos now’s your chance to subscribe to the Gardener Scott channel, if you haven’t already done so. If you like this video, you can give me a thumbs up and share it. I’m Gardener Scott. Enjoy gardening.

21 thoughts on “Understanding Wood Ash in the Garden – It’s Not All Good

  1. Here in the desert, gypsum is the key to lower ph and unlock the soils nutrients and of course compost, peat and mulch on top to preserve water. I use ash and gypsum at a 1:1 ratio twice a year.

  2. Very interesting! I bought a soil tester so ill see where im at now, i was going to douse my beds with all this ash ive been saving,when in fact i may not need to!

  3. Hi im new in gardening, i woundered is rice husk ash can also be use like wood ash? Any idea will be appreciated and a great help for me as a newbie in ganrdening

  4. Took a gamble and on a small stretch of my garden (3ft×40ft strip) I dumped my wood stove ashes with chunks of charcoal. Early in the spring I tilled it in deep. 1ft. Probably close to 50 gallons worth of ashes. That particular stretch has been out producing the rest. Flowering earlier and much more vigorous growth.

  5. This may sound rather unhygienic… would a urine (nitrogen rich) and wood ash tea be a good source of plant nutrition in acidic soils?

  6. I grow red wigglers. My suggestion is to feed the ashes to the worms first. They will break the nutrients down to a simpler form. Also, they will add microbiology and growth hormones.

  7. I have used ash from friends wood stoves or mine when I had one. But sparingly in two past gardens. My last soil test 3 years ago in this garden showed a  phosphorus level of 352ppm. for the veggie gardens, on the high level of optimal. 3 years before that 565 ppm. That was almost off the charts so I have used only lime in this garden to keep the ph above 6.0 to around 6.5. this next test will be in the late fall and I'll make some changes based on those results . How do you feel about using mineral supplements every 5 or 6 years ? May be  like Kozomite which seems to have a nice mix including green sand and crushed bathsalt rock . There are other brands available hear on the east coast. Like Azomite which is  easier to find locally  . I would value your opinion . Mike from Maryland

  8. pH value is just one indicator of some of the properties of your soil. It is like inflation rate. You cannot judge everything by looking at just one indicator. Wood ash contains a lot of essential minerals for all plants. Everything is a matter of concentration. If you add water to dilute these mineral compounds, you will have everything close to neutral, plus these minerals are readily absorbed by any plants. See even if you have hydrochloric acid, when you dilute it with tons of water, it will have a pH which is close to 7.0.

  9. Not only the wood ash just burned wood. It's all the minerals and nutritions the trees has sucked up..

  10. i have a very large pile of pine needles and was thinking about burning it and adding the ash to my compost. do you think that will be alright?

  11. Is this info strictly for wood burns only? Im using ash from my charcoal grill on my tomatoes. They seem to like it. Very tall and firm main stems, but not a lot of fruit. I'm not worried, i plan on wintering them this year.

  12. Useful information but presentation is so boring. Why not start in giving instruction in how to test your existing soil first, which is the most important point, then talk about how to use it and on which plants.

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