How To Trim & Transplant Mexican Fence Post Cacti

Dominating our front yard is a 20 foot tall Mexican Fence Post Cactus (MFPC). It was planted in 2004, and the previous owner - according to my neighbor's observations - 'used to be out there every morning spraying something on it'. My observant neighbor has MFPC planted at the same time, within a week of mine, and his is 6 feet tall with arms no bigger than a human's. My MFPC is bigger than Barry Bonds, or Toruk. Problem is, the tallest arm, has started to Lean towards my garage.
Cacti are heavy, and I don't want it to come crashing down on my domicile in a strong storm. The roofs here are tile, and I don't want to think about how much fun that would be to repair.

So I assembled my Cactus specific gardening tools 2 weeks ago, just before the massive January rains arrived.

• The hat not only guards against too much UV exposure, but it also warns the wearer when the head is getting too close to a spine covered arm is in close proximity just-behind the head.
• The news paper is essential for wrapping around the arms, to making holding them less painful. Double gloving is recommended, cloth under leather, to protect the digits.
• The inconel machete will get it's own post later this weekend - it's essential to have such a useful tool here in the desert.
  
• Safety glasses keep any splatter from accidentally getting in the trimmer's eyes.
• 10:1 diluted water to bleach solution (normal laundry hypochlorite) in a spray bottle is the universal cacti disinfectant recommended by the Desert Botanical Garden, post chopping.
• Not pictured above are 10 and 6 foot ladders, a long sleeved shirt, trousers, and large sheets of left over card board.

I originally theorized that if I lopped off the top of the tallest arm, it would relieve the most stress, torsional load, and prevent a toppling. I did a free body diagram in my head, and decided where the best lopping off points would be. However, there were several larger arms preventing my access to the top, so I lopped them off first.
One hand on the machete. The other hand holding the arm that is about to come down via gravity once it is severed from the main plant. Newspaper wrapped around the spiny arm to help reduce the pain of being stabbed by MFPC needles. A Strong Downward Chopping motion with a sharp machete, and you should be able to hack through the arm.
After all the arms are chopped off, use the spray bottle of diluted bleach solution to disinfect the open wound and prevent infection. 10% is just enough to kill bacteria but not to damage the soft cactus tissue. Apply liberally.

















Now, the main plant is safe, but what to do with the arms you just chopped off?

Well, you can try to compost them, but they are covered in sharp needles. Not a good idea. You Could throw them away, and my City of Phoenix curbside dumpster IS large enough to contain them, but that is such a waste. So transplanting these newest arms, planting them next to the previously truncated arms (from frost damage in early 2008) was the option chosen.

DBG recommends to let the amputated arms dry for a day or 2 in the shade, to discourage infection at the open wound. I used my garage and the card board to rest them upon. Transferred to the card board using newspaper wrapped around the arm, and double gloved.

A week later, a rack, pick, spade shovel, garden trowel, and cushion to kneel upon were in order. Rake away the rocks, trowel carefully, closely to the existing arms, dig gently with pick and spade so as not to severe the network of established roots that has webbed out just below the surface of the soil.


Set the arms into the carefully dug hole, with space between them. Use clods of clay to brace them. MAKE SURE to orient the arms so that the sides that were southerly facing on the main plant previously, are still southerly face in the new location. Also make sure on the arms that have had the tops lopped off, that the UP side is pointed up, and the plant side, is in the ground. the MFPC telomeres will have a hard time doing a 180 when they start to sprout new children off the arms in a few months. For a belt-and-suspenders approach, I tie a loose nylon support line around some established stakes and loop it around the new transplants just in case they begin to lean once the ground settles. The transplants will never be larger than the original parent - I don't know what the previous owner used to spray on them - but I feel better not throwing these arms out. And the whole amputation & transplant process actually took longer to blog about, than it took out in the front yard to execute!