Is Burnt Charcoal Ash decent fertilizer?

easttexgardenmanJune 8, 2007

Wanted to see if anyone has tried or knew if burnt charcoal ash is a good fertilizer. I was considering putting it around the root base of my toms and then watering it in but I wanted to ask on here from you experts out there before I did anything.


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it can be. it's a great source of potash, but it also changes yer soil's pH.

also, i wouldn't do it if it was the ash from briquettes, god knows what they put in those.

    Bookmark   June 8, 2007 at 6:35PM
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digdirt2(6b-7a No.Cent. AR HZ8 Sun-35)

For what it is worth, the FAQ over on the Soil & Compost forum says to avoid charcoal and its ash because of the chemical additives. It says don't even add it to your compost pile. But it's safety is debated somewhat so ultimately it is up to you.

Wood ash is ok if your soil ph will allow for it but I think I'd avoid the charcoal.

    Bookmark   June 8, 2007 at 7:58PM
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Ok, well It looks like I am going to stay away from the charcoal ash. :)

What about Used Coffee or Tea grounds. I always have a lot of this stuff put in the trash. Has anyone tried this?

Thanks everyone for your answers. I appreciate it.

    Bookmark   June 9, 2007 at 10:38AM
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yardenman(z7 MD)

Too many additives and odd chemicals in most charcoal. If you are using naturally-produced lump charcoal it is OK in moderation.

    Bookmark   June 9, 2007 at 4:35PM
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i seem to remember seeing or reading something where charcoal is bad for soil as in toxic?

    Bookmark   June 10, 2007 at 1:21AM
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pkapeckopickldpepprz(z9 a/b FL)

What if you use Royal Oak 100% natural wood charcoal? Maybe I am assuming it has no chemicals since it says 100% wood?

After reading the Terra Preta threads online and how fertile the soil was, I was curious to try this myself by crumbling a few briquets of this into a few gallons of my soil blend and see if it affects the plants I will grow in it.

    Bookmark   June 10, 2007 at 4:13PM
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I would wonder in that a lot of chemical compounds that are destroyed is done by burning, how could a chemical compound that you have just cooked your dinner on be bad to put in your garden after exposing it to the heat of actually burning the charcol.

    Bookmark   June 11, 2007 at 12:40AM
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Coffee grounds = AWESOME for tamatoes!!! Keeep with those and skip the ash!!!! I have been using them and my mother and grandmother use is the bomb for tomatoes and roses!!!

    Bookmark   June 11, 2007 at 5:51PM
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fcivish(Zone 6 Utah)

I don't know if you are talking about wood ash/charcol, or the ash from charcol briquets.

It should be noted that some of the richest soil found in the Amazon is what is called TERRA PRETA (which translates as BLACK EARTH). It only occurs in a few places. It turns out that is was DELIBERATELY manufacured, hundreds or even thousands of years ago, by the native indians who lived there. Scientists are studying it, to try to figure out what makes it so strong and rich, since, even now, hundreds of years later, it is greatly prized by farmers and growers in the region.

The process by which it was created is a real mystery, but one of the primary ingredients that they have been able to identify is wood ash.

It seems that the wood ash and bits of charcolized wood have the ability to grab and hold onto the nutrients and then give them up to the plants that grow in it.

    Bookmark   June 13, 2007 at 6:29PM
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Charcoal pH varies widely with the source and the pyrolysis temperature. High temp (1000 degC) hardwood charcoal has high pH, in the vicinity of 10. Low temp (300 degC) conifer charcoal has a pH near neutral pH. Low temp charcoal has pyroligneous acid condensates which partially account for the lower pH.

Here is a link that might be useful: pyrolysis posts at transect points, my blog

    Bookmark   June 16, 2007 at 4:30PM
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sunsi(z5 NY)

rdubow Quote:
"coffee is the bomb for tomatoes and roses!!"

I was going to say coffee grounds for roses but if it works for tomatoes too that's great got plenty of that :)

    Bookmark   June 17, 2007 at 7:26AM
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Coffee grounds are great anywhere in the garden!

Adds organic matter and it attracts earthworms too.

I put it by my tomatoes, roses, daylilies and hydrangias.

    Bookmark   June 18, 2007 at 2:49AM
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korney19(z6a Buffalo, NY)

Check the organic forum, I think there was a thread about charcoal, and a post with a link to actual ingredients found in a big brand name, maybe Kingsford.

    Bookmark   June 19, 2007 at 2:46AM
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I hear people saying briquettes because of all the chemicals. It that is true then should we be cooking with it. I only use Kingsford charcoal and briquettes.

    Bookmark   June 9, 2011 at 10:21PM
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Used kingsford charcoal ash on my blackberry plant. It didn't like it at all. Also killed surrounding grass. Didn't seem to bother my lime or banana plants though. Idk why.

    Bookmark   July 2, 2011 at 7:21AM
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I am currently in Philippines. the only fertilizer available is urea. So tried charcoal from the market, they use to cook with. Plants that had no growth for a year, (Palmagranet, and peppers) sprang to life, gaining height and body. Pepper's turned dark green then leaves wilted and growth stunted. I think it made the soil to alkaline. In time it begin to grow again. Tomatoes same effect, but not so pronounced. Plants triple in size, compared to not treated plants. My soil is river sand, tropical, acidic. very poor.

    Bookmark   July 8, 2011 at 4:45AM
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I used it on Boswellia Saca ( Frankincense tree) seeds mixed potting soil, pummice, and crushed charcoal and I got 1 to grow within a week ~ that being said Boswellia Saca prefers High Alkaline soil and is usually grown in poor soil and desert conditions and that is why I took the gamble on it working knowing the average germination rate of the seeds were less than 10% and that getting 1 out of 25 was a gamble any way but I got one so my guess is they are ok to use if the plant/tree requires high Alkaline soil just use it in moderation in comparison to the rest of the portions (not sure if I had a brick that had chemicals in it or not but it was a Kingsford briquet that was not burnt (chunks and powder from the bottom of the bag mixed and tested to get correct Alkalinity) and I got 1 to grow

    Bookmark   January 12, 2014 at 4:29PM
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seysonn(8a WA/HZ 1)

The things that is sold in nuggets form as charcoal, is made from COAL and not from wood. Plus they add additives to it to burn better.
The coal itself has no beneficial elements (Mostly C, S, some P ?).
But ash made by burning real wood charcoal, is the same as the wood ash that comes out of fireplace. It is highly recommended if your soil pH is under 6.5., and as long as it does not raise the pH over 7.

    Bookmark   January 12, 2014 at 5:21PM
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bcfromfl(z8a NW FL)

Anecdotally, I carry the WOOD ash from our fireplace out to a spot next to my compost piles to dump. There are all sorts of weeds and little bushy shrubs growing around the compost piles, but NOTHING grows out of the wood ash...and I've been dumping it there since 2006. Recently I've noticed some sheet moss taking hold over one side of the ash, but moss only grows on the top layer of things, and there could be a thin layer of dust or organic matter on top.

I would say at the very least, it's not worth the trouble, and based upon my unscientific experiment, it looks like any quantity of it in one place can suppress growth.

    Bookmark   January 12, 2014 at 5:51PM
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seysonn(8a WA/HZ 1)

... but NOTHING grows out of the wood ash...and I've been dumping it there since 2006.
That is quite normal and logical.

Wood ash, by itself, does NOT have all the ingredients needed by the plants to grow in it. Consider it as a source of some elements like potassium, Calcium etc. Compost is rich in nutrients and almost any thing that needed, to some extent.

When wood is burnt its organic properties are vanished. All is left i some of the INorganic elements.

    Bookmark   January 12, 2014 at 11:21PM
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bcfromfl(z8a NW FL)

I understand what you're saying, but given that there are already woody shrubs established all around the spot, one might expect them to eventually poke through from underneath.

True, it's a thick layer perhaps 4-5" deep, but the weeds aren't even creeping up to the edges...

    Bookmark   January 14, 2014 at 4:03PM
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seysonn(8a WA/HZ 1)

Another reason the plants might not grow in too much wood ash, could be a too high pH. Just guessing.

    Bookmark   January 17, 2014 at 7:18AM
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Wood ash is an excellent fertilizer in reasonable amounts. A layer several inches thick will have a ph so high that nothing can grow in it. Apply it to a small garden in amounts to correct existing low ph problems and it is a fantastic additive. The rules are simple, check soil ph, add charcoal to raise ph to a level plants are happy with. If you have alkaline soils, most likely you can't add wood ash.

There is a major difference between wood ash and the charcoal in tierra prieta charcoal soils. Charcoal has not been burnt entirely down. It is a highly absorptive material that holds nutrients. If you want to make homemade tierra prieta, you need a source of charcoal in large amounts.

    Bookmark   January 17, 2014 at 12:22PM
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yardenman(z7 MD)

Do not use charcoal ash or any burned wood with synthetic materials in your yard.

    Bookmark   January 19, 2014 at 4:47AM
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I use wood pellets over the winter. I know they have a binders added to them but they are generally cornstarch or plant gum. Any ideas if adding wood ash from wood pellets would be deleterious to the garden soil and if not, how many cups or pounds should be added per yard of garden soil?


    Bookmark   January 19, 2014 at 8:53AM
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