Reducing the height of a tall cactus

I have a 7ft columnar cactus.  I wondered if I could cut off the top 5 ft (which is the more healthy and attractive part of the cactus) and replant it so the top doesn't hit the ceiling? I can no longer fit it in my house.


Answer

One impediment to this plan is that the most successful size from which to regenerate growth with a columnar cactus is quite a lot smaller than your plant. No greater than 4 inches in diameter is a common rule of thumb. That is not to say that a larger cactus propagation will never be successful, but the opportunity for fungal infection or rot on such a large cut is higher and the and the chance of developing a root system quickly that is adequate to sustain a very large plant is far riskier. You are likely to be disappointed with the result.

It is also late summer at the moment, which is not an ideal a time for propagation. Spring or early summer are best, when the plant is in its strongest growth and will regenerate more quickly.

If the cactus is in great health, you have no other alternatives and you feel that there is nothing to lose in giving it a try, be extra strict with following the recommended technique. Use a sharp, sterilized knife to make the cut. The wound should be dusted with a fungicide, allowed to completely callus, and the new soil should be very gritty and fast draining. Do not bury the cut end in the soil, just place it on top. 

The bottom segment of the cactus can also generate new growth and with an intact root system will do so more easily. The new growth will be different from the old and resemble small cactus branches emerging from the top of the cut surface.

Courtesy of NYBG Plant Information Service

  • Last Updated Aug 05, 2022
  • Views 5
  • Answered By Leslie Coleman

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