Plant a cactus cutting the same way up as it grew: the end that was nearer the roots goes in the soil. If you cannot tell which end that is, consider planting the cutting on its side.
The short version
- The end that was nearer the roots goes down. The end that was nearer the growing tip stays up.
- A tip cutting has 1 cut end and a rounded, uncut top. The cut end goes down.
- A mid-section cutting has 2 cut ends. On San Pedro (a Trichocereus) and some other columnar cacti, the tall, ribbed, upright kinds, a small crease sits just above each cluster of spines. The crease is on the side toward the top.
- If you cannot tell the ends apart, lay the cutting flat on the soil. No end is buried, so there is no end to get wrong.
- A cutting planted upside down often roots poorly or not at all.
- If you planted one upside down, lift it. If both ends are dry and firm, turn it over and replant it. If the buried end is damp but firm, let it dry first. If it is soft, or has turned brown or black, do not replant it.
- Upright or flat, give an unrooted cutting no water until it has rooted. Rooting takes 4 to 8 weeks.
Why the direction matters
A piece of stem keeps its top and bottom after it is cut. This built-in direction is called polarity, and it is the same for stem cuttings of any plant.
It comes from a growth hormone called auxin. Auxin is made at the growing tip and moves through the stem in one direction only, away from the tip and toward the base. Where it collects at the lower end of a cutting, roots form. New shoots form toward the upper end.
Turning the cutting over does not reverse this. The end that was lower on the plant is still the end set up to make roots, even when it is pointing at the sky. Many growers report that cuttings planted that way root poorly or not at all.
Finding the bottom
A tip cutting is the top of a stem. It has 1 cut end and a rounded, uncut top with the growing point in the middle. The cut end is the bottom.
A mid-section cutting is a length of stem from below the tip, with a cut at both ends and no growing point. The 2 ends can look alike, so read the direction from the stem.
Look at the areoles, the small felted pads the spines grow from. On some Trichocereus, each areole sits just below a small crease that runs across the rib, like an eyebrow above an eye. The eyebrow is on the side toward the top of the plant. Hold the cutting so the creases are above the areoles, and the end at the bottom is the one to plant.
The crease is clearer on some stems than on others. Check several areoles on 2 or 3 ribs. If every crease is on the same side of its areole, you have your answer. If you cannot find a crease, or they do not match, lay the cutting flat. The same goes for a cactus of another kind that has no crease to read.
If you cut the pieces yourself, settle it at the cut: as each piece comes off, stand it upright the way it grew and leave it standing while it dries. Taking cactus cuttings covers the rest.
Planting upright
- Wait until the cut end has callused. A callus is a dry, firm, sealed surface across the whole cut face. A mid-section needs both ends callused.
- Use dry, fast-draining cactus soil. Set the bottom end in deep enough that the cutting stands on its own without leaning. A tall piece goes deeper than a short one.
- Keep it in light shade. Outdoors, the dappled shade under a tree is right. Indoors, choose a bright spot out of direct sun.
- Give it no water until it has rooted. Rooting takes 4 to 8 weeks when nights are about 60 F or warmer, and longer when nights are cooler.
- Watch for the signs of rooting: the stem plumps up, and new growth starts at the tip of a tip cutting or as shoots near the top of a mid-section.
How to root a cactus cutting covers callusing and the first waterings in full.
Planting flat
This is the method for a mid-section whose ends you cannot tell apart. A tip cutting has an obvious bottom and goes in upright.
Laid on its side, a mid-section tends to root along the side that touches the soil and send new shoots up from the side that faces the light. Cactus stems can root from this position.
When you do know which end is the bottom, upright is generally the surer choice. Flat is for when you do not know, or when you want a row of stems.
- Wait until both cut ends are callused.
- Lay the cutting on dry cactus soil and press it in until it no longer rolls. Most of the stem stays above the surface.
- Keep it in light shade, as for an upright cutting. A cactus lying on its side can sunburn along the upturned side.
- Give it no water until it has rooted. The timing is the same as for an upright cutting.
- Leave it where it lies. Turning it lifts the new roots out of the soil.
- Watch for the stem plumping up and for shoots along the upper side.
A flat cutting needs a container at least as long as the cutting, or a strip of ground. An upright mid-section fits an ordinary pot, and its new shoots come up close together near the top.
If you planted one upside down
Lift it out and look at both ends. Moving an unrooted cutting that has been sitting in dry soil generally does it no harm.
- Both ends dry and firm: turn it over and replant it, or lay it flat. Count the 4 to 8 weeks of rooting from the day you replant.
- The buried end is damp but still firm and its normal color: stand the cutting somewhere dry and shaded, with air moving around it, until the end is dry to the touch again. Then replant it.
- The buried end is soft, or has turned brown or black: do not replant it. Cactus rot covers what to do next.
- You are not sure it was upside down, and both ends are dry and firm: lay it flat.
Sources
Cutting Terminology, Polarity. University of Florida, Institute of Food and Agricultural Sciences, Department of Environmental Horticulture (a joint project of the University of Florida, University of Kentucky and Texas A&M University), 2023. https://propg.ifas.ufl.edu/05-cuttings/01-terminology/08-cuttingterms-polarity.html
Plant Hormones, Auxin. University of Florida, Institute of Food and Agricultural Sciences, Department of Environmental Horticulture (a joint project of the University of Florida, University of Kentucky and Texas A&M University), 2023. https://propg.ifas.ufl.edu/01-biology/01-hormones/02-hormones-auxin.html
PLSC 368: Lecture 9. North Dakota State University. https://ndsu.edu/pubweb/chiwonlee/plsc368/lecture/cpt10/cpt10cuttingbio.htm
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
How to Transplant a Cactus. Jack J. Kelly, revised by Michael Chamberland, University of Arizona Cooperative Extension, AZ1376, 2020. https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1376-2020.pdf
Vegetative Reproduction as Related to Biomechanics, Morphology and Anatomy of Four Cholla Cactus Species in the Sonoran Desert. Edward G. Bobich and Park S. Nobel, Annals of Botany 87: 485-493, 2001. https://www.eeb.ucla.edu/Faculty/Nobel/Reprints/333%20Bobich%20Nobel%202001%20Ann%20Bot.pdf