How to Salvage a Rotten Cactus

Ever wondered exactly how to salvage a rotten cactus? Unfortunately, we have! Whether you’ve over-watered a plant, or it’s contracted some drier form of fungus, etc., it’s important to excise the damaged or otherwise contaminated tissue as soon as possible. Doing this will maximise the chances of the plant surviving and hopefully recovering from rot or fungal attack.

Several years ago now, we noticed a small, black to brown and dry patch on one of the Trichocereus bridgesii monstrose clones from our personal collection. Considering that this didn’t appear to be the damp-to-soggy rotting commonly caused by overwatering (to which bridgesii is much more sensitive than other closely-related Trichocereus species) and that we’d never encountered such an attack before, we decided to experiment by letting nature take its course.

However – as is sadly apparent from the photos accompanying this tutorial – having decided this, we promptly forgot about this particular plant, due to both becoming completely engrossed in our other projects and to our foolish placement of this (quite small) plant behind many much larger specimens, hiding it from view. No water or TLC for this one for two or three months…not a situation that we would ordinarily encourage!

Moreover, while we only ever allowed this to happen in the spirit of inquiry (and only then because we have several genetically identical specimens of this great bridgesii form in our collection), when we finally remembered to check the plant, the dark patch had spread to the whole of the lower section, necessitating drastic action: the separation of the healthy-looking section from the entire affected area. This healthy section was then set aside to callous over, before being placed in a new growing container in which to strike roots.

There you have it – the story behind our no-nonsense guide covering how to salvage a rotten cactus! The basic technique described here works well for rooting most types of cactus species, whether cuttings made to salvage damaged plants, or simply to propagate desirable healthy genetics. Accordingly (and all conditions being favourable), we hope to see this poor bridgesii plant spring back into full health over the coming months!

How to Salvage a Rotten Cactus – Materials

  • Cactus (rotten or otherwise diseased)
  • Moler clay (or Perlite, etc.)
  • Sharp scalpel (or other suitable blade)
  • Plant pot (or other suitable container)
  • Potting soil
  • Water
Rotten Trichocereus bridgesii f. monstrosa 'Short-Stemmed' cactus

How to Salvage a Rotten Cactus – Method

  1. Prepare your cactus for the operation. If it’s growing as a small houseplant, as is the Trichocereus depicted here, gently remove it from its pot and clean off the bulk of the soil from the roots.
  2. Closely inspect the cactus to decide where to make your cut. You need to make sure that one hundred percent of the rotten/diseased tissue is removed, so it’s best to make an incision a five to ten millimetres above this, where the flesh appears normal and healthy.
  3. Take a clean scalpel and then position it at the point where you want to make the cut.
  4. Watching out for the spikes(!), firmly slice the cactus horizontally. To minimise the plant’s distress, it’s best to do this with as few cuts as possible.
  5. Once the healthy tissue is completely separated from the damaged part, inspect the newly exposed section carefully for any remaining signs of contamination. It’s often more widespread on the inside than may appear from the outside. For example, you can see from the accompanying photos that there was a bit of dodgy-looking tissue left when we made our example cut, which we sorted without further documentation.
  6. When you are sure that the cutting displays no obvious signs of rot/disease, place it somewhere dry in full sun to partial shade for its wound to callous over. Dependent on your climate, this can take anywhere from a week or so to two or three months.
  7. When you are satisfied that the cutting has calloused (or if it has visibly started to try to form roots already), you can plant it in a container of dry soil/volcanic rock mix to form roots. Bury the first few centimetres of the cactus. This is where the roots will form from.
  8. Place the cutting somewhere sunny and inspect every week or two to see whether roots have started to grow. Don’t water the cactus at all this occurs.
  9. Once the cutting has started to put down roots you can start to water it, although we recommend starting off by watering in cautious amounts, gradually increasing this over the next few applications to avoid rot while the plant’s roots are immature.

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