A healthy columnar cactus, the tall, upright kind such as San Pedro, can be cut to make new plants. The piece you remove is the cutting. The plant you cut it from is the parent.
The short version
- Cut in warm, dry weather, once nights are staying at about 60 F or warmer.
- Cut only from a healthy plant, through firm green stem, with a disinfected blade.
- Cut at about 45 degrees, then trim the base of the cutting straight across.
- Leave the parent's wound open to the air and keep water off it until it is dry and hard.
- Dry every cutting, pups included, somewhere dry and airy, in bright shade out of direct sun, until the cut end is dry, firm and sealed.
- Then root it. Give an unrooted cutting no water until it has rooted.
When to cut
Cuttings generally root well when nights are 60 F or above. The cut end spends weeks callusing and then rooting, so cut when the nights ahead will stay there. Check the forecast lows for the week ahead: you want them at or above 60 F, not a single warm night. Cuttings taken at the wrong time of year may be slow to root or may not root at all, so if your nights have dropped below 60 F, leave the plant whole until they warm up again.
Pick a dry spell as well. One cut leaves 2 open wounds, one on the parent and one on the cutting, and both have to dry. This matters most for a plant that stands outdoors in the rain.
Where to cut
A columnar cactus can be cut anywhere along the stem, so a cut partway down is fine.
Healthy tissue. Cut through stem that is firm and evenly green. Do not take cuttings from a plant that is shriveled, bruised, badly blemished, diseased or rotting.
Younger growth. Growth from this year or last year generally roots best. A stem grows from its tip, so the youngest growth is the part nearest the top. Older growth lower down may root less readily.
For length, many growers cut San Pedro pieces at least 6 to 8 inches long. A cutting from a large column can be several feet long. Leave healthy green stem standing on the parent.
Making the cut
What you need. A sharp knife with a blade longer than the stem is wide. If the stem is wider than any knife you have, use a clean fine-toothed saw. Cactus gloves, or a folded strip of cardboard or newspaper wrapped around the stem as a handle, let you hold a spiny stem steady.
Disinfect the blade. A blade can carry disease from one plant to the next. Wipe off any sap and dirt, then wipe the blade with 70% isopropyl alcohol so it stays wet for at least 30 seconds. Let it air dry. Disinfect before you start and again before you move to another plant.
Cut on a slant. Hold the upper part of the stem with the gloves or the cardboard and cut through at about 45 degrees. The slant is there to protect the parent: a slanted cut leaves less chance of water collecting and standing on the wound.
Trim the cutting flat. The same cut leaves a slanted face on the cutting. Trim that base straight across.
Mark the top. If you divide a long piece into several shorter ones, cut each straight across and put a small pencil mark near the upper end of each piece as you go. Once the tip is gone, the 2 ends of a middle piece look alike, and which way up a cactus cutting goes matters when you plant it. Every cut face on every piece has to dry.
Some growers dust a fresh cut with sulfur powder. It is not necessary. Keeping the cut dry, in moving air, is what matters.
Caring for the parent
Let the parent's wound heal by itself. Leave it uncovered, with nothing wrapped around it or painted over it.
Keep water off the cut surface until it is dry and hard to the touch. Water at the soil, not over the top of the plant, and move a potted plant under cover if rain is coming. Apart from that, care for the parent as you did before.
Look at the wound every few days while it dries. If the surface turns dark, soft and wet, or a soft patch spreads down the stem, that is rot, and it needs cutting out. See cactus rot for how.
What the parent does next
A cut column tends to send out new shoots at or near the cut, often more than one, and it may send up new shoots from the base as well. A single column can become a branched plant this way. New growth comes in warm weather, so a plant cut late in the season may show nothing until the following spring.
Removing pups
Pups, also called offsets, are small side shoots that a plant produces by itself. Left in place, a pup grows into an extra stem on the same plant. To make a separate plant instead, remove it as below. On a clumping cactus with rounded stems, they are the small globes that form around the parent, and removing them is the usual way to propagate such a plant. A columnar cactus may also produce pups, usually at the base of the stem. If your plant has no side shoots, skip this section.
Cut a pup away where it joins the parent, with a disinfected blade. Both the pup and the parent are left with a fresh wound.
Some pups grow roots of their own while still attached. A rooted pup still has an open wound where it was joined, so dry it like any other cutting before you pot it.
Callusing the cuttings
A cutting has to seal its cut end before it goes into soil. The dry seal is called a callus, and it protects the cutting from most diseases that live in soil.
Set each cutting somewhere dry and airy, in bright shade out of direct sun, with the cut end open to the air. A covered porch or the dappled shade under a tree both suit. Give it no water.
The callus is finished when the whole cut surface is dry, firm and sealed, with no damp, soft or shiny spots when you press it lightly. Go by that sign. The wider the cut and the cooler or damper the air, the longer it takes, and a full callus on a thick stem may take months.
Once the cut is sealed, the next step is rooting a cactus cutting. Give an unrooted cutting no water until it has rooted. Rooting takes 4 to 8 weeks.
Sources
How to Propagate Agaves and Cacti from Cuttings and Seed. Jack Kelly, University of Arizona Cooperative Extension, AZ1483, 2009. https://extension.arizona.edu/sites/default/files/2025-03/How-to-Propagate-Agaves-and-Cacti-From-Cuttings-and-Seed.pdf
Problems and Pests of Agave, Aloe, Cactus and Yucca. Jack Kelly and Mary W. Olsen, University of Arizona Cooperative Extension, AZ1399, revised 2011. https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1399.pdf
Cacti and succulents. Deborah L. Brown, University of Minnesota Extension, reviewed 2026. https://extension.umn.edu/garden-and-home/yard-and-garden/gardening-in-minnesota/cacti-and-succulents
Clean and disinfect gardening tools and containers. Julie Weisenhorn, Natalie Hoidal and Annalisa Hultberg, University of Minnesota Extension, reviewed 2026. https://extension.umn.edu/planting-and-growing-guides/clean-and-disinfect-gardening-tools