What Can Horticultural Charcoal Do in Gardening?

Horticultural Charcoal

Okay, horticultural charcoal does not absorb odors, enrich or purify soil, or ward off any insect (more on Myths of Horticultural Charcoal in Gardening).   So, what good does horticultural charcoal do in gardening?

Porosity – Improve Drainage

Charcoal is a porous form of organic matter primarily composed of carbon. It is used as a soil conditioner to improve soil drainage. This is especially true for those pots without drainage holes, for the charcoal will provide a place for excess water to settle.

Research has shown that growing mediums with horticultural charcoal are able to buffer the effects of sporadic watering, and help preventing the plants from damping off.

When compare with other moisture-retaining potting soil ingredients, horticultural charcoal has its advantages. Horticultural charcoal is in bigger chunks than perlite, yet light in weight. In addition, it doesn’t break down as quick as bark, nor does it rot. So, while horticultural charcoal does not purify soil or water, it is a good medium to retain moisture, improve drainage, and loosen up the mix.


Charcoal is organic, a characteristic which some gardeners place high in value.

Ease of Use

For those plants that are often transplanted from pot to pot for a fresh potting medium, horticultural charcoal and other coarse ingredients can be shake off from the roots very easily, so to be discarded and replaced.

Hold and Deliver Nutrients in the Soil

Horticultural charcoal can reduces the leaching of fertilizer in free draining soils as the charcoal’s porous carbon structure enables the nutrients to be held for slower release to the plants. The inclusion of charcoal in open seedbeds showed that it facilitates the uptake of nutrients. Researches have shown that calcium uptake almost doubles, with significant increases in potassium, magnesium and phosphorus, the pH increases slightly and there is an obvious increase in organic matter.

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5 comments to What Can Horticultural Charcoal Do in Gardening?

  • michael angel

    Increase in organic matter or increase in microbiological soil life “wee beasties”?

  • Perhaps it’s worth talking about biochar here? Esentially what we’re talking about is ethically produced horticulutral charcoal. To see what I’m talking about visit http://www.outbackbiochar.com for biochar information, biochar research and the latest biochar news. This wonderfully informative site has gardening tips with biochar, recent studies published all over the world and informative biochar articles. In addition you can purchase biochar for your home garden from Outback Biochar. Thank you in advance for your support and remember, if we all work together we can make real progress on climate change!

  • phil

    Thanks for this, I use charcoal for a polystyrene “rental” garden in Adelaide South Australia. It’s a drip feed stacking system (skies the limit!) with 1 drainage hole and without the soil saturates.

  • Mark

    Hi Sandy,

    I had some herbicide damage to my plants last year when I applied cow manure that had residual hormone based herbicides in it. I think it was the University of Nebraska that states adding activated charcoal to the soil to deactivate the residual herbicide. I will know by this planting season if it works, as last season it hammered all of my cucurbits.

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