Wally Richards – Condy’s Crystals: A gardening boon


Potassium Permanganate (Condy’s Crystals) has numerous uses in gardening as well as in other areas. I remember as a boy that if one had a sore throat a mild tincture of Condy’s Crystals would be made up to use as a gargle. This would hopefully kill the bacteria which was causing the sore throat. It was also extensively used as an antiseptic in pre-antibiotic days. We’ll stick to its uses in the garden for now.

Condy’s Crystals is great for:

  • club root in brassicas & other susceptible plants
  • control for moss in lawns
  • carrot fly deterrent
  • control powdery mildew in gardens
  • black spot & mildew on roses. 5 grams to 5 litres.
  • tomatoes: occasional watering with Condy’s Crystals will act as a tonic improving flavour and colour
  • sterilising soil
  • disinfectant
  • staining timber
  • fungus control on fish in tanks and ponds (using a very mild solution)

First though, a little history. In 1659 a German chemist, J.R. Glauber, fused a mixture of the mineral pyrolusite and potassium carbonate to obtain a material that, when dissolved in water, gave a green solution (potassium manganate) which slowly shifted to violet potassium permanganate and then finally red. This was the first recorded production of potassium permanganate.

Just under two hundred years later London chemist Henry Bollmann Condy had an interest in disinfectants, and marketed several products including ozonised water. He found that fusing pyrolusite with NaOH and dissolving it in water produced a solution with disinfectant properties.

He patented this solution, and marketed it as Condy’s Fluid. Although effective, the solution was not very stable. This was overcome by using KOH rather than NaOH. This was more stable, and had the advantage of easy conversion to the equally effective potassium permanganate crystals.

This crystalline material was known as Condy’s Crystals or Condy’s Powder. Potassium permanganate was comparatively easy to manufacture so Condy was subsequently forced to spend considerable time in litigation in order to stop competitors from marketing products similar to Condy’s Fluid or Condy’s Crystals.

Now, back to the garden…

Sterilising Soil
I originally came across the gardening use of Condy’s Crystals from a South Island gardener who told me how to apply the chemical for club root control in brassicas.

Dissolve a quarter teaspoon of Condy’s Crystals in one litre of water along with 3 desert spoons of common salt. Once dissolved the coloured mix is added to a further 9 litres of water and stirred to mix. One litre of this diluted mixture is then poured into each planting hole where a cabbage or other brassica is to grow. The preparation sterilizes the surrounding soil and reduces damage to the roots from the club root disease.

A number of gardeners like to sterilize the soil in glasshouses or in areas where the same crop is grown year after year, such as tomatoes. There are products such as Basamid that can do this and in the past many gardeners would use Jeyes Fluid which is also a sterilizing agent. The first is rather expensive and the second one is difficult to obtain these days.

My suggestion is to make up the above preparation as for club root but to use only half the amount of water thus doubling the strength of the solution. This then would be watered over 3 to 5 square metres of soil that you wish to treat. The soil should be moist but not wet prior to application. Leave for a week or so then water the area lightly to force the solution deeper into the soil. About a week or two prior to planting in the area, flood the soil to wash away any residue that may be left.

Moss Control
For moss control in lawns place one teaspoonful into 9 litres of water and spray over the moss. As an alternative to this mixture to control moss, use either Moss and Liverwort Control or Surrender.

Carrot Fly
To deter carrot fly add a few grains of Condy’s Crystals to water to make a light pinky colour and spray this over the young carrot tops.

Celery Rust
More recently another South Island gardener told me how he controlled rust on celery. At the first sign of rust a weak solution of Condy’s Crystals would be made up and sprayed over the celery for complete coverage. This would be repeated as needed. He told me that it worked a treat and as long as he used it, his celery would be rust free. I see no reason that the same can’t be used on any plants to control rust disease.

Fungus Control

This then can be extended to control of other fungus diseases such as black spot and powdery mildew. These can also be prevented or controlled with the use of Baking Soda. (Heaped tablespoon to a litre of water with one ml of Raingard added)

You could take this a step further and make up a winter-strength solution which would be the same as for club root and spray this over your roses and the surrounding soil to kill any disease spores that may be waiting for spring to attack. Other deciduous plants such as fruit trees could be treated in a like manner for various diseases such as curly leaf, black spot, brown rot and bladder plum.

It’s for you as gardeners to decide how effective these solutions turn out to be. They are my own suggestions and I would love to have feedback on any success or failure you may have.

One advantage is that Condy’s Crystals are cheap compared to many other sprays. A number of garden centres stock 150 gram jars of Condy’s Crystals sold under the correct name KmnO4 Potassium Permanganate. The jars are also available by mail order in areas where garden centres do not stock them. A few chemists may still stock Condy’s Crystals but from my research, few do – and these sell only small amounts (such as 25 grams for a price dearer than 150 grams from a garden centre).

Give it a try in any case, if you see a solution here to one of your problems – and let me know how you get on!

Problems ring me at 0800 466464 (Palmerston North (06) 357 0606)
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12 comments on “Wally Richards – Condy’s Crystals: A gardening boon

  1. Lorna Baxter on said:

    I shall try some of these uses. Thank you.

  2. Hi Wally – just wondering if it is okay to use Condy’s crystals as a dye marker for weedspraying…… I can see where I have been already?

  3. Mrs Diane Gower on said:

    Hi Wally,

    We have club root in our vegetable garden at Bell Block, New Plymouth. We have tried rotating the plants, not planting brassicas for 7-8 years, used Condy’s Crystals, rhubarb, lime etc and finally, this year we have decided to remove all of the soil from our vegetable garden and replace it with new topsoil, as well as completely cleaning out the compost bins, emptying all garden pots and sterilising the gardening tools.

    But there are a few questions we would like answered:
    a) how deep down do we need to remove the soil out of the garden?
    b) when can we start growing brassicas in the new soil?
    c) Is there anything else we should be doing?

    I look forward to your answers.

    Many Thanks

    Diane Gower

  4. Wally Richards on said:

    I beleive you would be wasting your time as the amount of soil to remove and replace would be too great and may not fix the problem as club root is a soil borne disease it has likely spread by movement and water to areas outside of the garden such as the lawn.
    Try the condys crystals as above article for growing brassicas. Do not use mustard as a green crop.
    Wally Richards

  5. Peter Grant on said:

    Hi Wally …

    Can I use Condis Crystals to get rid of Lawn Grub ?

    If so, what would be the recipe and best way to use it ?

    Regards …

  6. Hullo Wally, where do i buy condys crystals in Manawatu. I have tried chemists and some garden centres without any luck. thanks

    Mairi Isabeth

  7. Glenys on said:

    Hi Wally
    I am not a good carrot grower and read recently to add condys crystals at the time ofplanting the seed. Because I don’t use chemicals, is condys crystals safe to use?

  8. Melodie on said:

    It is absolutely wonderful in the treatment of fungal infection (blackspot on blades) of my lawn.  I use a teaspoon to a watering can leave the hose running in the can while I distribute over the lawn (light swinging motion) – I almost lost my back lawn entirely and after trying everything from commercial sprays, feeds, washing powder mixtures decided to try condi’s crystals.  100% recovery- and in fact better than before!!  Not so sure though if it would have any affect on my tortoises that roam free in the garden – anyone know??

  9. John on said:

    I think that creating better drainage would go a long way to prevent club root. This means building up the garden soil around 8 inches, using the condies crystal method, rather than removing it.

  10. Hi Wally
    I have black spot on the brassicas will condys crystals work. First time I have had this problem.

  11. Jerry on said:

    Hi Wally… where can I buy Condys Crystals… Thanks… Jerry

  12. leonie on said:

    Hi Wally hope you can help me I lost all my goldfish over the last six months ans was wondering if I can use condys crystals to clean out my outdoor pond, as Iam thinking of trying againg in the coming weeks after it settles Hoping you can help Many thanks Leonie

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