Wood Ashes in the Garden

March 11, 2010


YOU CAN FIND, in your fireplace, a valuable soil amendment. Wood ashes are rich in Potash, the very substance that raises the pH of soil, and therefore “sweetens” it. Sweet soil is the delight of lilacs; I swear my own shrubs flower so well in May because of regular wood-ash applications made beneath them in fall, winter and early spring. If your lilacs produce too few flowers, Potash can be the panacea they require. And here are other plants that prefer sweet soil:

Ornamentals:
Clematis, Gypsophila, Iris (tall bearded hybrids only); Japanese anemones, Lilacs, Madonna Lily, Nasturtium, Passionflower, Peonies, Phlox, Sweet Peas, Virginia Creeper

Herbs:
Lavender, Rosemary, Thyme

Vegetables:
Beets, Cauliflower, Cabbage, Leeks, Melons, Onions, Parsnips, Spinach

How much wood ash to use? This depends largely upon intuition. If you apply the ashes in fall, winter and early spring, as I do, you can hardly use too much; rain and snow dilute the concentration of Potash considerably. Here, I empty my thoroughly cooled fireplace ashes into a standard coal scuttle; when this is full, I pour the entire amount in a wide circle beneath the drip line of my mature lilac shrubs. For small ornamental, herb and vegetable plants, I pour about a cupful beneath drip lines.

For more definitive quantities, you must, of course, have your soil tested. Your county agent will leap at the chance to do this for you.

It is worth mentioning that Potash (and Lime, too) is a natural slug- and snail-deterrent. As I discovered last summer, these destructive mollusks abhor sweet earth.

Just take care when building a fire that you limit your burning material to hardwoods, and plain, not glossy, paper. Only these items are acceptable, after combustion, for garden use.

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Related Posts:
Tip: How To Find Free Mulch
How To Make Your Own Potting Soil
May Is For Lilacs

Comments

  1. Justin says:

    A friend of mine spreads wood ashes thinly on his lawn in spring. I don't know that it helps, but he does have a very nice, green lawn!

  2. Sally says:

    It makes sense that wood ashes would be good for certain plants. After all, forests (I've heard) regrow even stronger after a fire because there is more potash (and calcium, etc.) in the soil afterward.

  3. Adele says:

    Kevin, thanks for the tip. I will start spreading wood ashes around my big lilac. The ashes seem to have the same effect as lime.

  4. Randy J says:

    Kevin,
    As I use the wood stove for my primary heat source in the winter I end up with a lot of ash. After a mad dash to the garage in late November to get the hose, back to the house to hook it up, a run into the basement to turn the water on and a mad dash back out to the compost pile with the hose I learned that the ash must be REALLY cool before adding it to a huge pile of dried leaves! They burn really well! Now the ash goes from the stove into a coal scuttle for about 2 days then into a red wagon outdoors for another week or so and then into the compost pile. I haven't had such a manic morning since!

  5. Randy – Oh, my! One wants a compost pile to heat up, but not so much as you described! It's amazing how long the embers remain hot — even after they look ashen. Good thing you had water available!

  6. John Morrissey says:

    Another good topic you’ve hit on Kevin. I’ve spread wood ash on our lawn for years in place of lime and it seems to have a positive effect on it. My process is to sift it when I take it from the stove and store it in an old metal trash can until the summer and then I distribute it with a drop spreader (that’s why I sift it first, to remove any large charcoal bits that would clog the spreader). I also put some in our garden before planting in the late spring, but I don’t target specific plants. Based on your advice, I will save some specifically for the onions and spinach. I will also start spreading it around our lilacs before the snow hits.

  7. John Morrissey – And what good ideas you have — to save wood ashes in a metal trash can, and then to sift and spread them on your lawn. Great to have this free soil amendment, right?

  8. Chuck says:

    I’m really glad to know this. Thanks for the info

  9. Cary Bradley says:

    Off to spread wood ash, per your suggestion. Winter-sowing flowers also today. Busy bee. Thanks Kevin!

  10. amy says:

    I don’t have wood ash, but corn ash. We burn corn for heat, do you think that would work the same?

  11. Amy – That is a very good question, and one I unfortunately can not answer. I only know that wood ash contains potash, which sweetens the soil.

    But now I’m curious. Is the corn you burn in pelleted form, and intended for a wood-stove?

  12. diana says:

    I have been using wood ash on the driveway ice. After slipping on the ice a few times and the car slipping and sliding, I remembered someone telling me to use fireplace ashes on the ice. I could not believe how well it worked, INSTANTLY. And very much more environmentally safe than any ice melts on the market. It’s worth the extra carpet at the door (it does stick to the footwear). It doesn’t melt the ice, but it coats it, and stays with it until it melts on it’s own. Since we have had such a mild winter, I have plenty of ash in my can to use in the garden. Thank you.

  13. Diana – What a great tip. Thanks for sharing it here.

  14. Christy says:

    I was wondering, like Amy, about ash from a pellet stove. We use softwood (pine) pellets and there really isn’t much ash compared to our old woodstove, but why waste anything? Maybe I should just experiment on my lilacs. Think they would mind?

  15. slocan valley gal says:

    We have lilacs that have barely ever bloomed most probably from lack of sunshine and never being well pruned (except by the deer!) but I’m thinking of trying this! We heat our home with a wood stove and have a fair bit of ash thru the winter which my dad used to always throw on the flower bed out front (probably as it’s the closest bed to the house). I’ve been lazily dumping it in the bush near the house the last few years but think I will give it a try on the lilacs and put some in the garden for the onions. Thanks!

  16. Penster47 says:

    I have a large burn pit in the back of my yard where we burn yard waste, limbs and such. Used to burn leaves but I started a compost a couple of weeks ago and put what leaves I had in it. Mother Nature and the Wind raked most of them for me since we have had such a mild and dry winter!! :o ) I also put some of my woodchips from the limb chippers that were hired by the electric company to trim all the trees next to the lines in town and they were more than happy to dump a truckful in my yard! Free! yaaaaa. So, back to the original idea, I put some of the wood chips, some of the ash from the burn pit, and shredded newspaper in the compost along with some water. Plan on not using it until next spring, or maybe this fall. Depends on how fast it decomposes. But I will put some of the ash on my lilacs. I only have two small ones and they haven’t bloomed much, but they did bloom TWICE this last year. As I said, we’ve had a really mild winter for Missouri.

  17. KIM says:

    about the corn stove ash. have heard that it is good for all flowers so i’m thinking is like wood ash. olny difference i know about burning corn is it produces a sugar when it burns.

  18. Sabrina says:

    What a great website! I live in Alaska and we use wood as our primary source of heat. I recently discovered a site that suggested that you could add bones (leftover from cooking) to your fire to increase the value of your ashes for the garden. Since I buy bonemeal to add to my garden, this seemed to make sense to me. It reduces the amount of garbage we produce and the heat from the fire should be enough to address any bacteria concerns. Has anyone else tried this?

  19. Sabrina – Very interesting! And it makes sense. But would a bone would turn into ash if it were added to a regular fireplace-fire?

  20. Sabrina says:

    Kevin – Thanks for answering. I have been adding bones this winter to our EPA approved wood stove and when I remove the ashes….there are no large chunks of bone. We don’t have an open fireplace, so that may be different. I even put in a large bone from a ham and it turned to ash. I also add my egg shells and the yolks that are left when I am baking light. We’ll see how the garden reacts to this new addition. Still very winter, here but the sun is coming back strong….we are gaining 6 minutes a day!

  21. Jeri says:

    Kevin, You say wood ash “sweetens” the soil. Does that mean it raises the alkalinity or the acidity? I would love to use my fireplace ashes in my compost bin but we already have very alkaline soil and I was afraid that would make it worse.
    Thanks,

  22. Bob Daniel says:

    What about the ash from my charcoal grill? We use charcoal to cook and was wondering if this was okay for the garden?

  23. Robin Mavis says:

    We use natural lump wood charcoal in our grill instead of brickets. Can we use the ash from that? We don’t have a fireplace.

  24. Mel says:

    I noticed that you mention to only use hardwood in your stove. We live in an area where hardwoods are not plentiful so we burn pine and fir. We have been using our ashes for a few years in the yard and garden. My question is you mention to only use hardwoods. Is there a reason you restrict to hardwoods?

  25. Mel – My chimney-cleaning person told me never to burn soft wood in my fireplaces. And it is a fireplace (not a wood stove) that I am referring to in the above article.

    I suspect that with a wood stove, you have much more freedom to burn soft wood. A friend of mine actually adds green (unseasoned) wood to his stove! In any event, ashes from both soft and hard wood are perfectly fine for garden use.

  26. DAndrew says:

    Jeri, try using your spent coffee grounds on your soil to add some acidity. Works great here on the Rhodo’s and blueberries. If you live near a local coffee shop that uses organic coffee they may give you their spent grounds as well… Worth a try.

  27. Jill says:

    I have a ton of ashes and some lilacs that I would so like to have grow into beautiful mature plants..so I will be spreading the ashes. Thanks so much for this tip!

  28. Sandi says:

    Jeri,

    Sweet soil is acidic and alkaline in sour. Who knew. I googled it.

  29. Juanita says:

    Great tips! I learned about the benefits of using wood ash a few years ago. Now I save mine to add to my plants. So much more environmentally friendly and won’t harm the soil, an added benefit!!
    I started using my spent coffee grinds last year on my gardenia; I had so many yellowing leaves. I’m already seeing a greener bush! Then I learned I could use it on my azaleas as well Putting another waste product to good use!
    Thanks so much for all the great tips Kevin.

  30. Rose says:

    Kevin, today I was going to spread the ashes around my lilac. I have germander next to it. What will be the effect of the ashes on the germander?
    Thank you for your tips.

    Also, I like your pictures and I would like to take some pictures myself and send them to you. Would you be interested in having a folder for the fan’s pictures? I bet your fans would surprise and please you.

    Rose

  31. David H says:

    I made a mistake when I used my wood ash to fertilize my asparagus. It requires a balanced fertilizer and a later fertilization high in nitrogen. But here’s a tip that works well for me and is free. I save egg shells to plant with my tomatoes. Wash the egg shells, dry them thoroughly and then crush them by hand and store until planting time. Dig the hole for your plant and put a couple of tablespoons of crushed egg shells in the hole. Blossom end rot solved! FREE!

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