How to Take a Cactus Cut
Came across your excellent blog and had a question I could not find an answer for. There are lots of instructions and advice on how to cut portions off of a small cactus, but I have a large cactus that is about to grow through my eight foot ceiling!! I’d like some advice on cutting it in half and repotting the cut portion. I’d really appreciate any help you could give me. My guy looks like this.
Thanks in advance for your help.
Your Cereus is actually fairly easy to cut and re-root. You should be able to cut it at any height you like and then root the top cut as a new clone. The stump will eventually branch, so you should think about cutting somewhere about the height of the chair rail so it has room to grow in to a multi-branched tree form.
We use a pruning saw or a serrated bread knife to cut column cacti, cut at a slight angle with the down slope side towards the wall, so the scar is less evident on the stump. You can wrap the top piece you are cutting off with a towel or carpet scrap to make it easier to hold while cutting.
With the height it looks like it is a two person job, one holding the top and one using the saw. After you have cut off the top piece, spray or paint the cut ends with household hydrogen-peroxide to disinfect and help seal the injury. Re-treat daily for a couple of days to make sure it does not catch a fungus or bacterial infection. The top piece should be stood up against the wall on newspaper and let dry for a week. After a week the cut tissue should be scabbed over (think abrasion scab like after a bike crash…). Generally you don’t need rooting hormones for this type of cacti, but if you have some on hand or have any liquid kelp you could treat the cut end before potting it up to speed up rooting. If you use IBA rooting hormones only use it at low strength. Then pot up in dry cactus soil (fast draining and chunky). Stake as needed. Keep dry and warm for several weeks and then water.
It should grow roots in a month or two. If it starts to look dehydrated during this time frame you can mist the column at night with water. Cacti only open their stoma at night to transpire as it helps them preserve water in the deserts, so misting during the day will not help. You can give the stump a bit of low strength fertilizer to speed up branching and help it through the trauma of loosing it’s head.
Good luck and take care,